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- Introduction of the Blackhead Fireworm
2 UNITED STATES DEPARTMENT OF AGRICULTURE
) BULLETIN No. 1032
Contribution from the Bureau of Entomology —
L. O. HOWARD, Chief
Washington, D. C. Vv April 25, 1922
‘
THE BLACKHEAD FIREWORM —
) OF CRANBERRY )
ON THE PACIFIC COAST
BY
\ H. K. PLANK
Scientific Assistant, Fruit Insect Investigations
In cooperation with the Washington Agricultural Experiment Station, with.
Technical Deseription by CARL HEINRICH, Bureau of Entomology
CONTENTS
Introduction Seasonal History
Natural Enemies
Control Experiments
Recommendations for Control
Summary and Conclusions
‘Systematic Description of Rhopobota
naeverna Hiibner
Explanation of Plates
into the Northwest
Distribution :
Number of Generations
Description of Stages and Habits
WASHINGTON
GOVERNMENT PRINTING OFFICE
“1922 —
Vey re a
i PN
Via he
UNITED STATES DEPARTMENT OF AGRICULTURE
Contribution from the Bureau of Entomology
L. O. HOWARD, Chief
Washington, D. C. ay April 25, 1922
THE BLACKHEAD FIREWORM?: OF CRANBERRY ON THE
PACIFIC COAST.
By H. K. PLanx,’ Scientific Assistant, Fruit Insect Investigations, in cooperation
with the Washington Agricultural Experiment Station. (With technical
description by CArL HEINRICH, Bureau of Entomology..)
CONTENTS.
Page. Page.
TN EEOGU Ct OMs es erate es ee aS 1 | Description of stages and habits—Con.
Importance of the blackhead ANON ese ep SOE NS ate ae 16
ETL TN eee Peed cy ace 2 | Seasonal history__-—_—_ _— cane 19
The cranberry industry on the INEM EDURR NEN ene oo eS a ee 20
ISSUE GOMeRe ee ee a ae 2 Bardsitese 22 ae ae aoe 20
Features of bog management__ 3 Predacious enemies___________ 2ili
Phenology of the cranberry on Control experiments —_ Li 22
thembactie coast. 2 22a 3 Miscellaneous spraying experi-
Introduction of the blackhead fire- TCT RS yee 20 2s ee i ee De
worm into the Northwest_______ 4 Demonstration spraying experi-
DISGRID UNO N poe he wee ee ee 5 TNE MG See SE . Sacgey ow ae 26
Hood plants o2 = = ss ew ieal S aph Sate 5 | Recommendations for control] ______ 34
DM eStTRUChiveNeGcae ates Saye tt 5 IER TT Wahid i Sa Se ae 34
Number of. generations____________ 6 SS Duce sya pete ae pee pe rte lee 34
Descriptien of stages and habits__—_ |) Summary, and conclusions) =2222i25 37
iE oetinee septa Ge reid eo 2 A A 7 | Systematic description of Rhopobota
1 OGTR Ve Te ee eer ee es 9 VOCE EU DIME Ty aise erases areas movi 42
TUN epee es ee 14.1 Hxplanation of plates. ~—._.__=_— 45
INTRODUCTION.
Numerous complaints from Washington cranberry growers, re-
ceived by the Bureau of Entomology and the State College of Wash-
ington, led the two institutions to make a cooperative investigation
of cranberry pests in the Pacific Northwest in 1918 and 1919. In
this joint undertaking the writer represented the Bureau of Ento-
1 Rhopobota naevana Hiibner; order Lepidoptera, family Olethreutidae. Determined by
Carl Heinrich, of the Bureau of Entomology.
2 Appointed Collaborator, Tropical and Subtropical Fruit Insect Investigations, July 1,
1920.
T4890 °— 22 1
2 BULLETIN 1032,.U. S. DEPARTMENT OF AGRICULTURE.
mology and, successively, A. Spuler, Miss Orilla Miner, and Miss
Flora A. Friese the State C ollege of Washington.
IMPORTANCE OF THE BLACKHEAD FIREWORM.
The blackhead fireworm proved to be the most important cran-
berry pest of western bogs, and at the time the ravages of this insect
were first observed by the writer it was causing an estimated loss of
approximately 40 per cent of the combined crops of Washington and
Oregon. In 1918 this loss was reduced to approximately 15 per cent
and in 1919 to approximately 5 per cent, principally as a result of a
better knowledge of the life history and habits of the insect and more
general adoption of effective methods of control.
This bulletin reports the results of an investigation of the life
history and habits of the blackhead fireworm in the States of Wash-
ington and Oregon which was conducted during the years 1918 and
1919 from laboratory headquarters at Seaview, Wash. During this
period various methods of control were studied and thorcughly tested
under actual bog conditions.
THE CRANBERRY INDUSTRY ON THE PACIFIC COAST.
_ The town of Seaview, Wash., is located practically in the center of
the cranberry-growing district on the Pacific coast. In the State of
Washington this district comprises most of the peninsula of Pacific
County, in the southwestern corner of the State, directly north of the
mouth of the Columbia River. Here the industry was started on a
commercial scale in the early eighties by a French gardener named
Chebot, who set out about 35 acres to the McFarlin, Native Jersey,
Early Black, and Cape Cod Beauty varieties. Cuttings of most of
these varieties were brought in from Wisconsin, New Jersey, and
Massachusetts bogs. Some cuttings, especially of the McFarlin
variety, were doubtless brought in from Marshfield, Oreg., where
a Mr. McFarlin had started a bog 10 years aaieusl= with his own
selection of vines from the East, which bear his name. Extensive
planting, however, did not take place until 1912, from which time up
to 1915 large areas in southwestern Washington were drained,
cleared, and made available for cranberry culture.
Approximately 700 acres of cranberries are now in bearing in
southwestern Washington, with about 1,500 acres of peat land still
available for cranberry culture. In Oregon and the remainder of
Washington there is possibly a total of 1,500 additional acres of
cranberry land, about 300 acres of which in Oregon (in Clatsop and
Coos Counties) are now in bearing. Practically all the bogs of the
Pacific coast are sphagnum peat of various ages and thicknesses,
THE BLACKHEAD FIREWORM OF CRANBERRY. 3
found generally in swales between shore-sand ridges of slight ele-
vation.
FEATURES OF BOG MANAGEMENT.
Although considerable water sometimes collects on the Pacific
~ coast bogs, especially during winter, as a result of the heavy rains
from September or October to April, flooding as a distinct part of
cranberry bog management is rarely practiced in that section of
the country. Few bogs on the Pacific coast have a good supply of
water suitable for flooding purposes, and the mild winter climate in
the principal cranberry-growing region seems to obviate the necessity
of protecting the vines from winter injury. Principally is this true
in southwestern Washington. As a consequence many terminal
buds, especially on the warmer bogs, start to unfold shortly after
the vines reach maturity in September and October and a certain
amount of growth usually takes place during the warmer periods
of the winter. It rarely happens, however, that any material damage
is done by frost.
Covering the bog with water, usually from about November 15 to
March 1, is practiced only to a limited extent in Oregon, but where
this procedure is followed good results are usually secured. In the
southern sections of the State it is almost necessary to cover the
bogs with water during this period in order to keep the terminal
buds from pushing forth during the warmer periods of the winter
and meeting probable damage from frost during the late winter and
spring.
The application of sand once every few years, as practiced on
many eastern cranberry bogs, is not practiced on the coast, but prob-
ably could be employed with benefit. Inasmuch as the majority of
the bogs are located between sand ridges, an abundant supply of good
sand is readily available should its use become desirable.
PHENOLOGY OF THE CRANBERRY ON THE PACIFIC COAST.
The growth of the cranberry vine on the Pacific coast bogs 1s
exceedingly variable, as will be borne out by the data presented in
Table 1. This is probably because these bogs are for the most part
managed as dry bogs. The relatively variable weather in that sec-
tion of the country is also doubtless reflected in the early growth,
blooming, and fruiting of the cranberry. It is for these reasons
chiefly that no exact dates can be given for the various stages in the
phenology of the cranberry in that region.
4 BULLETIN 1032, U. S. DEPARTMENT OF AGRICULTURE.
An attempt has been made, however, after a long series of fre-
quent observations, to determine as closely as possible the approxi-
mate dates when these stages occur in their greatest abundance.
These dates are presented, therefore, in Table 1 for the earliest grow-
ing varieties, such as Early Black and McFarlin, and for the latest-
growing varieties, such as Howe. There seems to be considerable
variation in the growth of the varieties belonging to these two classes,
the height of each stage in the growth of the latest varieties gen-
erally coming a month after that of the earliest varieties.
TABLE 1.—Phenology of the cranberry on unflowed bogs on the Pacific coast,
based on observations at Seaview, Wash., 1918 and 1919.
Approximate date
of occurrence of
the height of each
stage on—
Stage of development.
The ear-| The la-
liest va- | test va-
rieties. rieties.
Buds breaking and new growth beginning to push forth.._._..................-.-.-- Apr. 6] May 7
Newuprigh trerowth nck co sinehyl on ees eee eee ae ee ees See ee eae Apr. 10} May 14
iIBlossomSan “hook Staee soho ss Gree Se ee ae EIR Daa ene a ie May 12] June 14
Mines metal DIOOmMen sass Taek ee ARE Reet eye oe Mey Wee tt te ee ee ene ee June 9} June 30
IBlosSomSialline@ and berries Seb Gms ee ee eee ee ee June 30} July 30
Such local influencing conditions as depth of vines, depth of the
underlying peat, or protection from the strong northwest wind which
commonly blows during much of the early growing season will, of
course, cause wider local variations than those here given. The
limits of each phenological stage are even more variable than the
height, it being not uncommon, for instance, to find blossoms on some
vines as early as May 12 and on others, many not yet fully opened, by
July 15. An early spring, too, would have the effect of somewhat
advancing the dates given in this table and a late one would prob-
ably delay the early stages a little, but the later stages, such as bloom-
ing and setting of berries, would probably be delayed to a less extent.
INTRODUCTION OF THE BLACKHEAD FIREWORM INTO THE
NORTHWEST.
Although the blackhead fireworm is found on the wild cranberry *
as far as 2 miles from any cultivated vines, the severest infestations
in Washington and Oregon are on bogs planted originally with vines
from Wisconsin, New Jersey, and Massachusetts. A study of the
history of the cranberry industry on the Pacific coast and of the
3 Specimens growing wild in southwestern Washington were submitted to Dr. F. L.
Pickett, of the Washington Agricultural Experiment Station and were determined by
him as the common western cranberry, Oxycoccus (oxrycoccus) intermedius, with the
following note: ‘‘ This is a little coarser than the small cranberry of the East, and
bears slightly larger berries.”’
Sen
THE BLACKHEAD FIREWORM OF CRANBERRY, 5
origin of the cuttings used furnishes convincing evidence that large
numbers of the eggs of this pest were brought into this region on the
leaves of cuttings from bogs in these three States. These cuttings,
principally from Massachusetts bogs, were used extensively in plant-
ing a large number of bogs set out in Washington and Oregon between
1912 and 1915, which was about the time the blackhead fireworm
became a pest of considerable importance in the regions from which
these cuttings were imported.
After the newly planted bogs had made sufficient growth, it was
the practice to mow them and use the cuttings thus obtained to plant
other areas, as these cuttings could, of course, be obtained at less cost
and in better condition than those from the East. So, helped in this
way, the blackhead fireworm spread over practically the entire region.
Once established on a bog it was a matter of only a few seasons until
this pest had overrun nearly every part of it and caused considerable
damage almost before the owner was aware of its presence.
DISTRIBUTION.
The blackhead fireworm is found on nearly every cranberry bog
on the Pacific coast. It has long been a pest of the cranberry in New
Jersey, Massachusetts, and Wisconsin, where it now causes as much
damage as any other cranberry pest and often more. According to
Fernald,‘ it has also been found on the cranberry in New York and
California.
FOOD PLANTS.
Numerous small larve resembling very closely in appearance those
of Rhopobota naevana were found feeding on some common bog
plants, such as “buck brush”*® and “sweet gale.”® None of these
proved to be the blackhead fireworm; and, so far as known on the
Pacific coast, Rhopobota naevana feeds only on the cranberry, both
native’ and cultivated.®
DESTRUCTIVENESS.
The injury to the cranberry by the blackhead fireworm is caused
by the feeding of the larvee, or worms, on the buds, foliage, blos-
soms, and fruit throughout the growing season. It is very charac-
teristic and quite unmistakable; there is no other pest of the cran-
berry on the Pacific coast the work of which is similar in all respects
*FWernald, C. H. A Synonyniical Catalogue of the Described Tortricidae of North
America North of Mexico. Jn Trans. Amer. Ent. Scc., v. 10, p. 48. 1882.
5 Specimens of this plant were identified as Spiraea douglasii by Dr. F. L. Pickett, of
the Washington Agricultural Experiment Station.
6 Also identified by Dr: Pickett as Myrica gale. ‘It belongs to the bayberry group.”
7 Oxycoccus (oxrycoccus) intermedius, the common western cranberry.
8 Oxyaoccus macrocarpus, the common cultivated cranberry.
6 BULLETIN 1032, U. S. DEPARTMENT OF AGRICULTURE.
to that of the blackhead fireworm, nor has the cranberry there any
other pest which annually destroys so much as this one.
The young larve start to feed on the newly growing tips shortly
after they hatch, in the months of April and May, and continue
their work throughout the growing season, attacking in greater or
less severity the buds, blossoms, and later the berries, injuring
the berries by boring into them and causing them to shrivel and
dry and often to fall from the vines. The most noticeable feature
of the attack of the fireworm during the middle or latter part of
the summer is the burnt appearance of the vines which results from
the work of this insect, suggesting the name fireworm. Since the ©
terminals are most affected, few if any fruit buds are set when the
vines are badly infested, and as a result nearly all the crops of the
current season and of the following year are~destroyed by the
feeding of the larve during a single season. The vines, while never
completely killed, are very much stunted and by the end of the
summer are left stripped of the majority of the leaves. They are
often brittle, and in the case of long-standing infestation are short
and scrubby with numerous short and crooked branches as a result
of being prevented from making a natural terminal growth. From
this condition they do not usually return to their normal produc-
tiveness until good control work has been in force for several years.
NUMBER OF GENERATIONS.
By rearing the insect from the winter egg stage in an outdoor
shelter it was found that it passes through two generations and
sometimes a partial third. For example, the hatching of the winter
eggs starts the first generation, and the resulting larvee which change
into pups and moths also belong to the first generation.
The eggs that these moths lay start the second generation. Con-
trary to the behavior of this pest in the East, only about four-fifths
of these eggs hatched to form a second generation the same season in
which they were deposited. The remaining one-fifth did not hatch
until the following spring.
All the eggs deposited by the moths resulting from the second set
of individuals are known as the eggs of the third generation. So
far as is known, in eastern cranberry regions the eggs of this genera-
tion do not hatch until the following spring. On the Pacific coast,
however, it was found that about one-third of the eggs of this gen-
eration hatched late in the summer, forming a third generation of
larve. Because of adverse weather conditions toward the latter
part of the season, none of these larve developed into pups and
moths. This generation is therefore called a partial or incomplete
generation.
)
THE BLACKHEAD FIREWORM OF CRANBERRY, 4
DESCRIPTION OF STAGES AND HABITS.
THE EGG.
The egg of the blackhead fireworm is smooth, slightly elliptical,
with the center partially raised and rounded. It measures approxi-
mately 0.65 millimeter wide, or about the size of the head of a very
small pin. When first laid it has a slight opalescent sheen and a
light lemon-yellow color which changes to a deeper yellow in about.
two weeks. The hatched egg is more inconspicuous, being trans-
parent and appearing much like a small drop of albumin which has
dried on the leaf. (Fig. 1.)
Fic. 1.—Eggs of the blackhead fireworm moth on the undersides of the cranberry leaves,
enlarged 7.5 times: a, Winter eggs; b, eggs in the * black-spot”’ or first stage of devel-
opment ; c, hatched eggs. :
HIBERNATION,
4
The eggs are laid by the parent moth singly or in groups on the
underside of the cranberry leaves; rarely, a few eggs will be found
deposited on the upper surface of the leaves. On the badly infested
bogs as many as 10 or 12 eggs may be found on the underside of a
single leaf. The majority of the wintering eggs are usually deposited
on the leaves on the lower portions of the vines, the short, low up-
rights near the ground generally containing the greatest number
of eggs. During picking season and the following winter, many of
these leaves are dislodged from the vines, and it is not an uncom-
mon thing to find them on the bog floor bearing numerous eggs. An
infestation may easily be distributed from one part of a bog to
:
8 BULLETIN 1032, U. S. DEPARTMENT OF AGRICULTURE. %
another by these leaves drifting from place to place over the bog in
and on the water which sometimes collects during the winter time.
Instances were noted in which numerous egg-bearing leaves had been
washed into a corner of a bog, where they almost covered the vines.
These eggs, being the first affected by rising temperatures. were the
first to hatch in the spring, and the young larve had almost com-
pletely destroyed the surrounding uprights before eggs elsewhere in
the bog had hatched.
INCUBATION AND HATCHING.
The first signs of incubation are noted as the black head and tho-
racic shield of the developing larva begin to show through the chor-
ion or eggshell. As development progresses the young larva may be
seen to move within the egg and finally, as it grows in vigor, to rup-
ture the egg wall at a point over its mandibles and gradually escape
by means of a wriggling sidewise motion through this slitlike open-
ing, which is near the top of the upper surface of the egg. (Fig.
1,6, ¢.) It usually takes from about 3 to 5 minutes for the larva to
free itself entirely from the eggshell.
FActTorRS INFLUENCING HATCHING AND DEVELOPMENT.
(a) Temperature—Temperature has the greatest influence on the
fireworm eggs as well as on the other stages. This varies more than
is generally supposed among different bogs, depending upon location.
(0) Depth of vines—Another very important factor which tends
to retard or hasten development of fireworm eggs is the depth of the
vines in which they are deposited. A bog with thin vines will warm
up more readily in the spring and maintain a higher temperature
generally throughout the season than a bog with rather thick vines.
Observations show, for instance, that on bogs with thin vines, hatch-
ing generally starts during the first warm days of spring (sometimes
late in March or in early or mid-April), reaches its maximum early
(say towards the latter part of April), and produces moths in maxi-
mum numbers in the middle or late part of June. Ona thickly vined
bog, in the same locality, however, and under similar conditions of
temperature and moisture, hatching, while it may start about the
same time as it does on the thinly vined bog, will be only desultory
until the vines have warmed up considerably. Hatching in maximum
numbers may not take place then until the middle or latter part of
May. This in the absence of a winter flooding distributes hatching,
on bogs with a medium or heavy growth of vines, over a considerable
period.
(c) Drainage—During the winter or rainy season more or less
water usually accumulates on the majority of the cranberry bogs
THE BLACKHEAD FIREWORM OF CRANBERRY. 9
on the Pacific coast. On those which are not quickly and easily
drained this winter water remaining on the bog late in the spring
causes the vines_and the fireworm eggs to be rather slow in de-
veloping, with a consequent grouping of the hatching and develop-
ment of the first generation of larve.
THE LARVA.
The newly-hatched larva of the blackhead fireworm (fig. 2, a) is
about 0.1 mm., or a little over one-thirty-second of an inch in length;
at first it has a pale yellow color which turns to a darker yellow with
age, and has a relatively large dark brown or black head, accentuated
by the thoracic shield, the first segment back of the head, which is
nearly as dark as the head; hence the name “ blackhead.”
Fic. 2.—The blackhead fireworm: Views of the larva, enlarged 7.5 times: a, Newly
hatched larve: b, dorsal, lateral, and ventral views of full-grown larve.
When fully grown (fig. 2, 6) the larvee measure about 6.5 mm., or
about one-fourth inch in length, and are dark greenish yellow with a
coat of darker olive green above. The head and thoracic shield
are black. The larve are very active from the time they are about one-
fifth to one-fourth grown and vigorously wriggle from their gal-
leries when disturbed, falling to the ground and quickly concealing
themselves among the trash and leaves beneath the vines by a char-
acteristic sidewise and backward movement of the body. They are
provided with three pairs of thoracic legs, four pairs of abdominal
legs, and one pair of anal legs. Depending upon the weather and
the time of the season, the blackhead fireworm spends from 10 to
about 75 days in the larva state,
74890 ° —22—_2
10 BULLETIN 1032, U. S. DEPARTMENT OF AGRICULTURE.
é
FEEDING HABITS.
A newly hatched larva begins feeding shortly after it leaves the
ego, but may wander about for from 15 minutes to half an hour be-
fore taking any food. It usually starts feeding on the underside
of the leaves, generally near the eggshell from which it has just
emerged. At first it bites into the epidermis of the leaf, and, mix-
ing the nibblings with the thread of silk which it spins continuously
from several points beneath its lower lip, soon covers itself with a
Fig. 3.—The blackhead fireworm: Characteristic work of the newly hatched larye on
the underside of cranberry leaves.
greenish brown material which has the appearance of fine sawdust.
For a time it continues to chew into the leaf, feeding principally be-
tween the upper and lower surfaces, acting in many respects hike
aleaf-miner. (See fig. 3.) This is particularly characteristic of the
early-hatched larvee of the first generation. The larve of this gen-
eration which hatch later, and usually those of later generations
hatched in warmer weather after the new growth is weil out, pro-
ceed almost directly to the tip, spending very little time as leaf-
miners.
(T
THE BLACKHEAD FIREWORM OF CRANBERRY. _ 11
Depending upon the prevailing temperature and the condition of
the weather at this time, the young larva in a somewhat dormant con-
dition spends two weeks, more or less, in its burrow, feeding only
when the weather is warm and favorable. If the weather is warm it
will be quite active and may stay in its burrow only two or three days.
On badly infested bogs it is a common thing to find the underside of
the lower leaves on the vines badly chewed and full of burrows. The
majority of instances of this type of injury are doubtless caused by
the larva hatching early in the spring before the bogs have become
sufficiently warm to permit active feeding, and also by those hatching
late in the fall, as is often the case on account of the bogs being ex-
posed to the weather the year round.
At the approach of warm weather, or after the young larva has
grown larger and stronger, it leaves its burrow and proceeds toward
the tip of the upright. Here, if the weather should turn cool, it
starts to feed in the whorl of leaves about the terminal fruit bud and
incloses itself in a loosely constructed web of frass and silk, either
between two terminal leaves or between the bud and the adjoining
leaf, where it awaits more favorable conditions which may cause the
terminal bud to break and grow. As these conditions become intensi-
fied the larva proceeds to web up the unfolding leaves as it feeds
on and skeletonizes them from within. From about the latter part
of May or the beginning of June this injury is noticeable to the
casual observer, many of the short, new uprights assuming a withered
and bent-over appearance at the tip, similar to those shown in the
accompanying illustration (fig. 4).
As the weather becomes warmer and the vine growth increases the
fireworms, the majority of which at this time (about early June)
may be nearly one-half to three-fourths of an inch long, feed rapidly
on the leaves in their web galleries, gradually extending them or
moving to an adjacent tip or upright as new food is needed. The
vines gradually assume the characteristic dried, hight yellow-brown
appearance, and as feeding continues the bog begins to look as
though a fire had swept over it, scorching the tips of the vines,
which by midsummer are dry, reddish brown, and often nearly
leafless; whence the name “ fireworm.”
On a-vigorously growing bog the late-hatched larve of the first
generation often feed upon the unfolding blossoms and newly
formed berries, sometimes causing them to drop from the vines. In
their feeding the young larve frequently burrow into the blossoms
at a point near the base of the petals and feed on the floral organs
within, or they may bore into the ovary directly from the outside.
This feeding is first noticed about the time when the blossoms are
in the “hook stage” or about the beginning of June on the early
bogs. At this time a few very small larve usually may be seen eat-
12 BULLETIN 1032, U. S. DEPARTMENT OF AGRICULTURE.
ing into the blossoms or berries, as described above; later on, both
large and small larve may attack the berries, eating into them
where the berries touch one another or the leaves or an adjoining
upright. (See fig. 5.) :
The second generation of worms makes its appearance in consid-
erable numbers the latter part of July. These larvee not only feed
upon the foliage, like those of the first generation. but they also web
it up more, feed longer, and move from place to place much oftener
than do the larve of the first generation. Especially on bogs
Fig. 4.—The blackhead fireworm. Early work of the larve in the tips: a. Entire new
tip destroyed: b, showing how the tip leaves are webbed together: c. an uninjured
upright.
making little new growth they may extend their feeding to the old
foliage, including many of the old uprights in their webs. In
addition, many of them may also feed extensively throughout the
remainder of the season on berries of all sizes. It does not seem to
make much difference whether the berries are webbed up or not; in
fact, the majority of the berries attacked are not webbed up at all.
(See fig. 5.) The injury done by the second generation of larve is,
therefore, very striking. The third generation of worms is not very
distinct from the second and not quite so numerous; but occurring
THE BLACKHEAD FIREWORM OF CRANBERRY. es
later in the season, when the vines are maturing, these larve feed
principally on the berries, and therefore do more immediate damage
to the crop if any remains on the vines.
The result of the work on all three generations is not only the de-
struction of the current season’s crop or its material reduction but
also the loss of a considerable proportion of the crop the following
year, the setting of fruit buds being largely prevented by the attack
of the larve on the terminals. It will thus be seen that the fireworm
in one season can very materially reduce the cranberry crop of two
f
seasons.
Fic. 5.—The blackhead fireworm: Injury of the larve to the berries. The large berry on
the upright is uninjured.
PLACE OF PUPATION.
After the larve have reached their full growth they usually leave
the webbed uprights and descend to the trash and leaves beneath the
vines, where they inclose themselves between several old leaves in more
or less loosely constructed cocoons, typical specimens of which are
shown in figure 6. Sometimes, however, especially in the case of the
larve of the first generation, some may spin themselves up within
a thin cocoon in the tips of the uprights, as shown in figure 7. Very
14 BULLETIN 1032, U. S. DEPARTMENT OF AGRICULTURE.
often some larvee, after feeding in a cluster of berries, will spin their
cocoons and also pupate on the inside of one of them, or they may
fasten their cocoons between the berries, mixing their silk with frass
and any skeletonized leaves available. This is commonly true of the
larvee of the second generation. It is not very unusual, therefore, to
find some berries with the empty pupa cases protruding from a hole in
the side. The great majority of the larve of all generations, how-
ever, descend to the ground to pupate.
THE Cocoon.
As previously referred to, the cocoon of the blackhead fireworm is
composed of strands of silk which the larva fastens to any surround-
ing objects, as frass, leaves, or berries, and more or less loosely draws
Fig. 6.—The blackhead fireworm: Typical cocoons formed out of dead cranberry leaves
beneath the vines. The ones in the top row have been opened to show the interior;
those in the lower row show the empty pupa cases protruding. All slightly enlarged.
about itself preparatory to pupation. The interior of the cocoon is
shown in figures 6, 7, and 8. It is in cocoons similar to these that the
larvee pass through a resting period followed by a final molting of
the larval skin. This resting and molting, during which the pupa or
chrysalis is formed, is called pupation.
THE PUPA.
The pupa or chrysalis of the fireworm is about 5.5 mm. or a little
less than one-fourth inch long by 1.5 mm. or about one-sixteenth inch
wide, and of a light amber yellow color immediately after casting the
larval skin. This color soon changes to a deeper amber brown, and
in pup about to change to adults the color is a very deep amber
approaching almost black. The pupz are not usually encountered
without a rather close examination of the leaves and trash beneath
(T
THE BLACKHEAD FIREWORM OF CRANBERRY, 15
the vines in which, as already mentioned, most of the individuals
of all generations pupate. (See fig. 8.)
The pups wriggle considerably when first picked up, moving the
end of the abdomen in a circular motion, but they have no power of
locomotion such as the larve have. Just before the moth is ready to
emerge, and in order that it may do so without hindrance, the pupa,
Hig. 7.—The blackhead fireworm: Pupa in cocoon spun in a tip of a cranberry upright.
Enlarged 6 times.
_by means of this wriggling motion and with the aid of a number of
small backwardly directed spines arranged in double rows around the
back of each segment of the abdomen, forves itself out through the
end of its loosely spun cocoon until the thorax and the tips of the wing
pads are free of the edge of the cocoon. (See last specimen at right
in lower row of fig. 6.)
16 BULLETIN 1032, U. S. DEPARTMENT OF AGRICULTURE.
The duration of the pupa stage varivs from 10 to about 65 days,
depending upon the weather and the tinie of the season.
THE ADULT.
The adults, or moths, of the blackhead fireworm are conspicuous
because of their habits of flight; when disturbed they often rise in
very large numbers. Upon close examination they are found to be
small in size, measuring in length from the tip of the head to the
tip of the wing on the average about 6 or 7 mm., a little over one-
fourth of an inch, or about the same length as the mature larve.
With the wings spread they measure about 10 mm. across, or a little
over three-eighths of an inch.
The moths (fig. 9) differ somewhat in color, seeming to vary espe-
cially according to age. The first pair of wings of freshly emerged —
‘Hig. 8.—The blackhead fireworm: View of pupa and interior of cocoon. Enlarged about
7.5 times.
and unrubbed specimens have a ground color above of deep silver
eray, with irregular markings of brown, which often give them a
golden-brown sheen. Characteristic markings of a single row of
short alternating brown and silver-gray bars running diagonally to
the front margin are found on the first or upper pair of wings. The
second or lower pair of wings of the female are without characteristic
markings; those of the male have an irregular dark spot on the under-
side near the front margin. The second or lower pair of wings of
both male and female have a fringe of long, bristlelike scales extend-
ing from near the tip along the back margin to the body. The abdo-
men is medium and slender, depending on the sex, female specimens
having a somewhat broader and shorter abdomen than the males. The
abdomen and the legs are covered with dark silver-gray scales, which
their habits of flight.
THE BLACKHEAD FIREWORM OF CRANBERRY. Li
often have a light golden-brown sheen. The antenne are about one-
half the length of the body and more or less bristlelike.
The adults live from 3 to 83 days after they emerge, and during this
time eat little or nothing, except, perhaps, a little nectar from the
blossoms, or water in the form of dew or rain.
HABITS OF FLIGHT.
After the moth emerges from the pupal case it rests for a short time,
during which the wings are spread and dried. It then starts to fly |
and moves rather swiftly in a short, jerky, darting motion, making
usually only short flights from place to place over the vines. . Par-
ticularly on heavily infested bogs the moths are very conspicuous for
They will often be seen
to rise in large numbers
when disturbed, as by
spraying or by a person
walking through the
vines on a warm after-
noon, suggesting to some
the appearance of a>
cloud.
PERIODS OF ACTIVITY.
A few moths may
generally be seen flying
from tip to tip almost
every hour of the day
from the time of their
first appearance in June Fic. 9.—The adult or moth at rest on a cranberry up-
right. Enlarged about 6 times.
until late in September
and October, but the time of day they are most active is from about
3 o'clock in the afternoon until after dusk. During this period,
especially if the weather is warm, they may be seen to rise in the air
for a few feet, making their characteristic short, jerky flights.
MIGRATION.
It is in the moth stage principally that the blackhead fireworm
spreads itself over the bog or invades an adjoining one. The moth,
however, flying only short distances, would not naturally migrate
more than several yards from its original region of activity; but,
helped by the wind, it is possible for it to be carried as far as several
74890°—22 3
18 BULLETIN 1032, U. S. DEPARTMENT OF AGRICULTURE.
hundred feet in one flight, and it is thus that bogs neighboring badly
infested ones, especially to the leeward, may become badly infested
in a few seasons. Bete .
Other ways in which the fireworm is disseminated over a bog have
been mentioned, namely, in the egg state, on leaves floating over the
bog in the winter water (p. 7-8), and also on cuttings (p. 4-5).
PROPORTION OF SEXES.
In 1918, of 158 moths of the first generation emerging in the in-
sectary, 81, or 51 per cent, were males, and 77, or 49 per cent, were
females; of 59 moths of the second generation, 24, or 41 per cent,
were males, and 35, or 59 per cent, were females. In 1919, of 101
moths of the first generation emerging in the insectary 53, or about
52 per cent, were males, and 48, or about 48 per cent, were females;
of 52 moths of the second generation 24, or 46 per cent, were males,
and 28, or 54 per cent, were females. This shows a slight predomi-
nance of males over females in the first generation and the opposite
in the second generation.
COPULATION.
Copulation usually occurs shortly after emergence. Of those pairs
observed in the rearing shelter, one was found copulating the same
day it emerged, two the day after emergence, and one pair did not
copulate until 7 days after emergence. The same pair was never
seen to copulate more than once.
The period of copulation varies in length, the minimum period
observed being 1 hour and 26 minutes and the maximum 26 hours and
55 minutes. The male of one pair observed was noted dead and still
attached to the female 3 days after copulation was first observed.
OVIPOSITION.
Egg-laying commences shortly after copulation, usually within a
few days. During oviposition the female rather quickly pushes the
egg out through the tip of the abdomen, which she holds very close
to the underside of the leaf. Here the egg, a soft, plastic drop, settles
over the surface and soon assumes its ordinary flat, oval shape. The
outermost covering, which is rather moist when the egg is first laid,
dries and cements the egg to the leaf and gives it its appearance of
being glued on. (See fig. 1, a.)
TIME OF Day WHEN OVIPOSITION OCCURS.
Eggs may be laid at almost any hour of the day and evening when
the weather is warm and fair. However, in order to determine the
time of day when the moths were depositing eggs in largest numbers,
(D
THE BLACKHEAD FIREWORM OF CRANBERRY. 19
32 males and 42 females of the first generation were collected from a
cranberry bog on July 15, 1918, and immediately confined as follows
in three battery jars 9 inches high by 5 inches wide: Jar No. 1 con-
tained 12 males and 12 females; jar No. 2, 10 males and 12 females;
jar No. 3, 10 males and 18 females. Each jar was provided with a
few inches of slightly moist sand on the bottom, an abundance of
clean cranberry uprights, and a sponge moistened with a weak solu-
tion of sugar and water for food and moisture, |
Every 3 hours from 2 a. m. to 9 p. m. daily until July 20 the up-
rights in each jar were replaced with fresh ones and the eggs on them
and on the side of the jar counted and recorded. The sponge was
also moistened daily.
The number of eggs found deposited at each examination is sum-
marized in Table 2. As will be noted therein, eggs were laid during
every period between examinations, but the largest number of eggs
was deposited between 3 p. m. and 9 p. m., 663, or 39.6 per cent of
the total, being deposited between 3 and 6 p. m., and 650, or 38.8 per
cent, between 6 and 9 p.m. The smallest numbers were deposited in
the 12-hour period between 9 p.m. and 9a.m. It will be noted fur-
ther that the time of day during which eggs were deposited in largest
numbers is also the period of greatest activity on the bog.
TABLE 2.—Number of eggs of bluckhead fireworm moth deposited every 3 hours
from 6 a. m. to 9 p. m. by moths of the first generation confined in battery
jars; Seaview, Wash., July 15 to 20, 1918.
Number | Per cent : Number | Per cent
Period of deposition. of eggs of total Period of deposition. ofeggs | of total
deposited.) deposited. ; deposited.|deposited,
i| |
psamsto Gasms sie oe 7 ARGUE Sep wriasit OFGuoase ae eee | 663 39.6
apm tO Oden = 8 yt Gaps ite OVO, pe Imes ee ee | 650 38.8
9a:m.to12noon.._.......... 67 4.0 —
L2TVOOM-tOVE pS Mao ee) ao 209 12.5 To talesitce. Cia sane ss | 1, 675- 100.0
The number of eggs found deposited at each examination is shown
in graphic form in figure 10, together with a curve showing the hourly
temperature during the period of the experiment. Attention is here
drawn to the influence of the temperature on egg-laying. It will be
noted that the largest number was deposited between 3 and 6 p. m. on
July 16, a few hours after the highest temperature, namely, 75° F.,
was recorded.
SEASONAL HISTORY.
It was noted that larve of the first generation appeared in greatest
abundance on the bogs about the latter part of May, the pupe toward
the middle of June, and the moths about the first or second week
in July.
90 BULLETIN 1032, U. S. DEPARTMENT OF AGRICULTURE.
Because of the overlapping of the generations, one can scarcely do
more than speculate as to the date of occurrence of the stages of the
second and third generations on the bogs; and the latest dates of the
occurrence, particularly of the moths of the first generation and all
the stages of the second and third generations, could only be obtained,
therefore, by rearing methods.
NATURAL ENEMIES.
PARASITES.
INSECTS.
Although numerous very small wasplike insects (members of the
order Hymenoptera) can be seen flying over the tops of the vines on
: | : s
(2 a
:
Ny
Q
g
all
8
ai alee
8
NUMEER OF ECCS CEPOS/ITEDO
~
8
| =
HL =
Ah
i.
3 g g
WOURLY TEMPERATURE (NV CEGREES FARENHE/T.
|
i
| | ‘\ | i “+ ---- | ‘ |
Ord yaaa el yey ed jay ES ES } eee SEs AY ai Oo
LMT 6 GIZF 6 YEMTZ © PsE3B 6 XLMTEA OC PIZFT CO YMTB OS PIAP 6 FEMTAO FIZ FT O FEMED 6 FID OC YOMTZC
SULLY 15 - SULYIE SLLY/7 SAYS SULLY 19 SLLY2O Shy eal
Fig. 10.—Egg deposition by blackhead fireworm moths of the first generation. Records
every three hours from July 15 to 20; Seaview, Wash., 1918.
badly infested bogs on warm, clear days, none of these could be reared
from collections of the eggs and larve of Rhopobota naevana from
various bogs. Circumstances indicate very strongly, however, that the
blackhead fireworm on the Pacific coast is parasitized, to a certain ex-
tent at least, although not as much as on some dry cranberry bogs in
the East.
Funcous DISEASE OF THE PUP.
From about the beginning or middle of August it is very common
to find, especially on the older and more badly infested cranberry
bogs, areas of 3 to 5 inches or more in diameter of old leaves beneath
the vines which have the appearance of being smeared with a floury-
white substance. Closer examination of these areas will show that
this whitish appearance is due to the fruiting growth of a para-
sitic fungus, which attacks and kills the pup concealed in their
cocoons in these old leaves. This fungus is shown growing from the
° Determined by Dr. A. T. Speare, of the Bureau of Entomology, as a species of Spicaria.
THE BLACKHEAD FIREWORM OF CRANBERRY. OA i
cocoon in the lower row of specimens in figure 11. The specimens in
the top row have been dissected from the loosely constructed cocoons
and show the fungous disease growing on the pupe.
While this disease certainly causes the death of a large number
of pupe on bogs where it is prevalent, not too much reliance should
be placed on it in the control of the fireworm, since the greatest, part
of the damage by the fireworm is done to the vines before the time
when the fungous disease 1s growing rapidly. The weather also
may or may not be favorable to its rapid growth, and hence its
killing power and spread are Ne to vary considerably from one
season to another.
Fig. 11.—Fungous disease, a species of Spicaria, growing from the blackhead fireworm
pupz in their cocoons. Slightly enlarged.
PREDACIOUS ENEMIES.
SPIDERS.
On the cranberry bogs of the Pacific coast spiders of various kinds
are found in very large numbers and doubtless devour many fire-
worm larvee and moths.
INSECTS.
A large number of “ladybugs” are also seen on cranberry bogs,
and their presence there sometimes causes alarm to a grower who is
not familiar with their habits. One species, the California red
ladybird beetle,?° is very common, and both larve and beetles can be
seen actively walking over the tips of the cranberry uprights any
+20 Specimens determined by Mr. E. A. Schwarz, of the Bureau of Entomology, as
Coccinella californica Mann.
92 _ BULLETIN 1032, U. S. DEPARTMENT OF AGRICULTURE.
time throughout the summer. The ladybird beetles, with few excep-
tions, are beneficial insects; the adults of this species have been
observed to feed readily on the larve of the blackhead fireworm in
captivity, and in the field doubtless consume large numbers of this
insect.
CONTROL EXPERIMENTS.
Since most of the cranberry bogs on the Pacific coast can not be
provided with a sufficient supply of water for use in control work,
insect pests on these bogs should be combated largely by the applica-
tion of insecticides in the form of a liquid spray. This method seems
especially desirable against the fireworm after a study of its habits
and methods of feeding. It may also be necessary to do more or less
spraying for certain fungous diseases at various times throughout
the season, and some of the dates for these applications may corre-
spond to a great extent with the time of application in the control
of the fireworm. The grower, therefore, can combine the materials
used for the control of the fireworm with those necessary for fungous
diseases whenever: the times for these two applications coincide, and
thus save the expense of separate applications.
_ All the control experiments against the blackhead fireworm were ©
arranged, therefore, so as to include tests under actual bog conditions
of several methods of spraying the eggs, larvee, and adults with a
number of promising insecticides, both with and without spreaders,
at various times throughout the season. These sprays were applied
by the types of nozzles shown in figures 12, 18, and 14, all the tests
being so planned as to shed some light on questions concerning the
number of applications, the best materials to be used, the amount of
spray material which should be used per acre, and the most effective
manner of applying it.
MISCELLANEOUS SPRAYING EXPERIMENTS.
In Table 3 is given an outline and the results of the miscellaneous
spraying experiments conducted on Howe vines on the Portland-Sea-
view Cranberry Co. bog at Seaview, Wash., in 1919. Very similar
experiments were performed on this bog in 1918, but the severe infes- ©
tations previous to that season had so reduced the bearing power of
the vines that few blossoms were set in 1918, and the results therefore
were not wholly dependable. They showed, however, a decided in-
crease in control by the use of insecticides combined with spreaders,
such as soap or glue, as compared with the same insecticides applied
without the addition of these wetting agents. They also suggested
that a solution of 40 per cent nicotine sulphate, used at the rate of 1
part to 1,000 parts of water, with the addition of fish-oil soap at the
rate of 2 pounds to 50 gallons and applied at the rate of about 300
(D
THE BLACKHEAD FIREWORM OF CRANBERRY. 23
gallons per acre, might be just as effective as the same kind of a solu-
tion in which the nicotine was used at the rate of 1 part to 800 parts
of water and applied at the rate of about 200 to 250 gallons per acre.
The miscellaneous spraying experiments conducted on this bog in
1919 were therefore planned in the light of the results of the pre-
vious season. |
TIME AND NUMBER OF APPLICATIONS.
The odd-numbered plats, I to XV inclusive, received 3 applica-
tions on the dates shown in Table 3. - The first application (May 13
and 14) was made to catch the largest possible number of small larvee
in and near the tips of the uprights before they had a chance to web
up the new unfolding leaves. The new growth at this time was ap-
proximately three-fourths of an inch long. The second application,
June 12, was made to kill the next lot of larve hatching after the first
application and came about the time when the majority of the blos-
soms were in the “hook stage.” In order to catch the late-hatching
larvee the third spraying was made July 1 and 2 as the vines were ap-
proaching full bloom. The even-numbered plats, from II to XVI
inclusive, and plat XVII, received in addition to these applications
just described one more apphcation (July 16 and 17) about the time
the moths were flying on this bog in greatest abundance. The pur-
pose of this fourth application was to kill these moths and also any
larvee which had moved into the tips at this time.
While the frosts of May 4, 5, and 6 somewhat reduced the crop on
nearly all the plats, the comparative results, as obtained by the ex-
amination of the berries from 3 circular areas of about 100 square
inches, each picked at random over each of the plats, strengthen the
observations made of these plats at various times throughout the
season.
TABLE 3.—Outline of miscellaneous spraying experiments in the control of the
blackhead fireworm on the Portland-Seaview Cranberry Co. bog at Seaview,
Wash., 1919.
Nl
Number of gallons used calculated per
acre per application. Total Total
number | number Gain
Plat | Spray materials, dosage, | of ber- | of ber- auer
No. etc. Aver- ries. |rieSfree check
May 13 ned July 1 | July 16] age per} exam- from :
and 14. ‘| and 2. |and17.| appli- | ined. | injury.
cation.
?
j
(oe 40 per cent nicotine sul-
phate, 1-1,000+fish-oil Per cem.' Per cent.
Soaps 2-505. fe. onc 380 300 S20 a | eeteepe | 333 | 388 92. 52 | 15. 50
TE Sas | 40 per cent nicotine sul- 7 | |
phate, 1-1,000-+fish-oil | ‘ | ung
SOaDp 220088 oe 5h 55a 380 300 320 480 370 | 402} 95.52 | 18. 50
Ili_...| 40-per cent nicotine sul-
phate, 1-800 + fish-oil | Z aes Z
SUa pis 2-00) ee sas 330 280 ssi 0) 0} lean eee 297 | 735 93.74 | 16.72
VES 5) 40 per cent nicouine sa | | |
te, 1-800 -O1 ; = as
a. al aes 2 peathakd. Cs 330 280 280 480 342 | 737 97.42 | 20.40
94 BULLETIN 1032, U. S. DEPARTMENT OF AGRICULTURE.
TABLE 3.—Outline of miscellaneous spraying experiments, etc.—Continued.
|
Number of gallons used calculated per
acre per application. Total Total
number} number Gain
Plat | Spray materials, dosage, | of ber-| of ber- suces
No. etc. Aver- ries | ries free check
May 13 Tame 12 July 1 | July 16] age per} exam- from :
and 14. *} and 2. |}and17.} appli- | ined. | injury.
cation.
|
Vie era ae 40 per cent nicotine sul- |
phate, 1-600 + fish-oil Per cent.| Per cent.
Soaps 2=00 22 es eee eae 295 270 Path Ua Bie ey 278 820 91.21 14.19
VI....| 40 per cent nicotine sul-
phate, 1-600 + fish-oil
Soap, 2-50.........- warts 295 270 270 500 333 485 94.22 17.20
VII...| Powdered arsenate oflead,
450+ fish-oilsoap , 2-50. 340 | - 300 2002 eet ae 300 401 83.04 6.02
VIII. .| Powderedarsenate oflead,
23-50-+ fish-oilsoap, 2-50. 340 300 260 450 337 172 76.16 - 96
IX....| Nicotine oleate, 1-300-.... 295 270 ZC OS aes 278 433 91.45 14. 43
DCS See Nicotine oleate, 1-300-...-- 295 270 270 320 289 862 91.99 14.97
XI....| 40 per cent nicotine sul-
phate, 1-800-+ glue, 1-200. 290 280 S103| See 293 703 83. 64 6.62
XII...| 40 per cent nicotine sul-
phate, 1-800+ glue, 1-200. 290 280 310 620 375 600 86.16 9.14
XIII..| Nicotine oleate, 1-400..... 300 320 170 )s| naan eres 32. 1,012 92.29 SG H7/
XIV .-.| Nicotine oleate, 1-400..... 300 320]. 350 660 407 1,061 91.42 14. 40
XV ...| Nicotine oleate, 1-500..... 330 380 3203 |2es A 343 793 87.64 10. 62
XVI.-| Nicotine oleate, 1-500... _. 330 380 320 600 407 827 92.38 15.36
XVII.| ‘‘Phenoleompound”’ No. 5
00 RSE ee a Se ee 420 560 320 560 460 628 73.56 3.46
XV Check untreated ae=<5 4: |- S25 salSe ates alae ne oe See one Sere ae 74 CEZAR eee eens
| |
| is }
NotE.—Mist nozzles as shown in figure 13 used for allapplications, with hand barrel spray pump giving
pressure of 50 to 100 pounds,
NICOTINE SULPHATE.
The conclusions drawn by Scammell"! regarding the effectiveness
and safety of 40 per cent nicotine sulphate in the contro] of. the
blackhead fireworm were borne out in the work on the Pacific coast.
Of the various strengths used, 1 part to 800 parts of water with 2
pounds of fish-oil soap to each 50 gallons of solution, applied 4 times,
seemed to give the highest percentage of cranberries free from fire-
worm injury; it will be noted in Table 3, however, that 4 applica-
tions of this material, used 1 to 1,000, gave nearly as great a gain
over the check. The fact that it gave a higher percentage of clean
fruit than 1 to 600 was probably due to the fact that there was a
larger setting of fruit on this plat and perhaps a somewhat lighter
infestation than on the one treated with the solution of the strength
of 1 to 600.
NICOTINE OLEATE.
Nicotine oleate was made by stirring together the proportions of
a 40 per cent solution of free nicotine and oleic acid according to
the directions given by Moore” as follows:
1 Scammell, H. B. A New Method of Controlling the Blackhead Fireworm. Jn Proce.
47th Ann. Cony. Amer. Cranberry Growers’ Assn. (Aug, 26, 1916), p. 8-12; Cranberry
Insect Problems and Suggestions for Solving Them, U. S. Dept. Agr., Farmers’ Bul. 860,
p. 4-9, 1917.
122 Moore, William. A Promising New Contact Insecticide. Jn Journ. Econ, Ent., v. 11,
no. 3, p. 341-342, 1918.
THE BLACKHEAD FIREWORM OF CRANBERRY, 25
Two and one-half parts of a 40 per cent nicotine solution unites
with 12 parts of commercial oleic acid or red oil. Four and one-
fourth parts cf this soap will then contain 1 part of nicotine or will
equal 24 parts of the 40 per cent nicotine solution.
It will thus be seen that nicotine oleate is a nicotine soap made
from a fatty acid and nicotine; as such it has the spreading properties
of a soap and in addition it is a contact insecticide which can gener-
ally be used in place of the ordinary 40 per cent nicotine sulphate
and soap solution for cranberry spraying. It could not be mixed,
however, with hard water or combined with Bordeaux mixture or
any other alkaline solutions; and since it takes 41 parts of the
nicotine oleate to equal in nicotine content 23 parts of the 40 per cent
nicotine solution, about twice as much nicotine oleate as 40 per cent
nicotine sulphate had to be used to equal one part of the latter.
A spray material of this character, which has combined in it
both soap and nicotine, would greatly facilitate the control of the
fireworm, if not materially reduce the cost, wherever its use is prac-
~ ticable.. Solutions of the strengths used seemed to spread equally
well over the cranberry foliage. As shown in Table 3, it was used
at the rate of 1 part to 300 parts of water, 1 to 400, and 1 to 500,
about equal, respectively, to 1 to 600, 1 to 800, and 1 to 1,000 of the
40 per cent nicotine sulphate formulas. Both three and four appli-
cations were made of each strength. The largest percentage of —
fruit free from fireworm injury seemed to be obtained where nicotine
oleate was used at the rate of 1 to 500 and applied four times. There
is very little difference between the results of this plat (plat XVI)
and those secured-on plat XIII where nicotine oleate 1 to 400 was.
applied three times. This is partly explained by the fact that the
fireworm infestation was more thinly scattered over the former plat
than over the latter. The results where nicotine oleate was used
at the rate of 1 to 300, while apparently very satisfactory, are not
so good, considering all factors, as where it was used at the rate
of 1 to 400.
ARSENATE OF LEAD.
' As in 1918, arsenate of lead proved to be of little or no value in
the control of the fireworm, the foliage being badly eaten and nearly
all the berries destroyed by the worms, even where four applications
were made with the addition of soap.
WETTING AGENTS oR ‘“ SPREADERS.”
That the presence in the spray liquid of some material like soap,
which will make it wet or spread over the smooth, waxy foliage of
the cranberry, seems to make considerable difference in the control
26 BULLETIN 1032, U. S. DEPARTMENT OF AGRICULTURE.
results obtained was plainly shown by the preliminary experiments
of 1918 previously referred to. In 1919, therefore, a comparison
of the kinds of spreaders was made and in these tests glue. 1 pound
to 200 gallons, and nicotine oleate at the strengths mentioned above
were checked against fish-oil soap, 2 pounds to 50 gallons. As will
be observed in Table 3, the use of glue gave the poorest control of
the three groups of plats III and IV, XI and XII, and XIII and
XIV, in all of which the strength of the nicotine was approximately
the same; nicotine oleate was next; and fish-oil soap, 2 to 50, gave
the best results. vas
Observations made immediately after these spreaders were ap-
pled showed that glue spread the solution fairly well over the old
foliage, but failed to carry it into the small, new leaves at the tip,
the region of greatest activity of the young larve: nicotine oleate
spread very satisfactorily over both old and new foliage, but did not
seem to go as far into the unfolding buds and leaves as did the solu-
tion containing fish-oil soap, which, moreover, might be one reason
for the superior control secured where fish-oil soap was used as a
spreader. ;
It was observed that fish-oil soap used at this strength would
often carry the solution containing it into the very center of the
group of small unfolding leaves at the tip of the upright and enable
the solution to find its way into the loose web of any small larve
which might be working therein.
‘““ PHENOL COMPOUND No. 1.”
A proprietary compound used primarily as a disinfectant and
containing a large amount of crude carbolic acid was tested against
the fireworm. This material mixes in all proportions with water,
making a milky white solution which gives off a strong, characteris-
tic carbolic-acid odor. It was used at the rate of 1 part to 500 parts
of water and sprayed directly into the tips of the vines, as on the other
plats. As will be noted in Table 3, little or no control was secured.
DEMONSTRATION SPRAYING EXPERIMENTS.
The results of a series of demonstration spraying experiments,
conducted on the bogs belonging to H. M. Williams & Sons, at
Ilwaco Junction, Wash., in 1919, are presented in Table 4. The ma-
terial found most effective in previous tests, namely, 40 per cent
nicotine sulphate, 1 to 800, with soap 2 to 50, was used in all these
experiments.
THE BLACKHEAD FIREWORM OF CRANBERRY. Pag
TABLE 4.—Outline of spraying experiments in the control of the blackhead fire-
worm on the H. M. Williams & Son’s bog at Ilwaco Junction, Wash., 1919.
A ? | MM
Number gallons used per | § Ber ostuce | s
acre per application. aes aes S)
Ss | worm injury. s 5
g ; : >
Spray materials, dosage Tae | eB : ® d }
nozzle, and variety of | |@ |2 |B |&8 F : 38 g a S ke,
cranberry. Ses esse ees isis Ss a So re e 2
Seilret 35 | XS PS SS] OS) ita eel a Bl) © >
Z SAG | Bel Dede Th [eel eet anne [een iba S BS a
2 SY ISRIES SS ISS] BS] (SSe/ ea | g is} =
S& a= g |s i) >al 6 Sas| 62 3 & 3
~ Wea WS Sr) fd Mista Ss o Pats ie el
Gee Per Lipo ct.| Per ct.| Bush. | Bush.
A....| 40 per cent nicotine sul- | 378 | 378 | 418 |-_-.. 391 | 1,071 | 54.44 | 89.35 | 30.27 | 31.32 | 18.52
phate, 1-800 + fish-oil
soap, 2-50, mist nozzle,
Howe variety. |
B....| 40 per cent nicotine sul- | 457 | 666 | 444 |..-... 522 | 1,355 | 58.67 | 89.74 | 30.66 | 46.98 | 34.18
phate, 1-800 + fish-oil |
soap, 2-50, Bordeaux
nozzle, Howe variety.
Cree 40 per cent nicotine sul- | 300 | 389 | 257 | 417 | 341 | 1, 238 | 62.52 | 93.05 | 38.10 | 56.99 | 40.88
phate, 1-800 + fish-oil
soap, 2-50, ‘‘spray gun,”’) ©
Howe variety.
D....| 40 per cent nicotine sul- | 300 | 389 | 257 |..-.. 315 | 1,499 | 54.30 | 84.25 | 29.30 | 75.06 | 58.95
phate, 1-800 + fish-oil
soap,2-50,‘‘spray gun,”’
Howe variety. |
E....| 40 per cent nicotine sul- | 300 | 327 | 267'| 268 | 290 | 1,075 | 45.30 | 87.72 | 46.16 |176.88 | 161.85
phate, 1-800 + fish-oil
soap, 2-50,*‘spray
McFarlin Sree.
F....| 40 per cent nicotine sul- | 300 | 327 | 267 |..-.. 298 | 1,162 | 41.22 | 77.45 | 35.89 |124.65 | 109.62
puss. 1-800 + fish-oil
soap, 2-50,‘‘spray gun,’
McFarlin cease :
G....| 40 per cent nicotine sul- | 563 | 697 | 884 | 643 | 697 | 1,345 | 69.00 | 91.97 | 50.41 |168. 84 | 153. 81
phate, 1-800 + fish-oil d
soap, 2-50, Bordeaux
sozzle, McFarlin vari-
ety.
H....| 40 per cent nicotine sul- | 499 | 388 | 499 | 554 | 485 | 2,343 | 56.50 | 93.81 | 52.25 |364. 26 | 349. 23
phate, 1-800 + fish-oil
soap, 2-50, mist nozzle;
McFarlin variety.
ASRS Checksomsleex oie wlatsiNy ses. ees lover eee 479 | 44.88 | 59.08 {..-...- 12280) eee ee
and B, Howe variety,
untreated (for check on
plats A and B).
22 Check on lee of plats C |.....|.....|.....|..--- |poroees 626 | 43.93 | 54.95 |.....-- UGE Neesoose
and D, Howe variety,
untreated (for check on
plats C and D).
eee Check-onleevof plats) H lisase|e 5-22 \be en cles see eee AAS ES3=don|i4e oO nee NEES Woscseos :
and H, McFarlin vari-
ety, untreated (for
check on plats E, F,
|
|
’ : | |
_——
Here an effort was made to test the three types of nozzles, namely,
the Bordeaux, the mist type, and the spray gun, on as large a scale
as possible, and to approach commercial spraying conditions. The
plats selected ranged in approximate size from one-fourth to one-half
acre and included the Howe and McFarlin varieties. These were
previously badly infested with the fireworm and yielded few or no
berries in 1918. Figures 12, 13, and 14 show these three types in
actual use, and Table 4 shows the number of gallons per acre used
in spraying with each type of nozzle, with a pressure of about 250
pounds at the tank. A stationary power outfit was used for all the
applications, pipes being used to convey the spray liquid from the
pump to the plats.
28 BULLETIN 1032, U. S. DEPARTMENT OF AGRICULTURE.
Plats A and B constituted one section, containing about an acre
of vines, C and D another to the south, and E, F, G, and H a third
to the east of C and D. Since the infestation of these three sections
varied somewhat it was thought advisable to have a check plat meas-
uring 1 by 2 rods for each section. As noted in Table 4, they were
placed to leeward of the plats of which they acted as checks to pre-
vent the unnatural spread of moths over the plats. These were num-
bered 1, 2, and 3, respectively. |
The percentages of berries free from fireworm injury, as shown in
Table 4, were obtained from an examination of the berries picked at
harvest time from five circular areas of approximately 100 square
inches each, selected at random on each sprayed plat. Berries were
examined from three such areas on each of the check plats.
The yield of each plat was obtained by measuring its entire crop —
as picked at harvest time. Plats A, B, C, and D were picked with a.
scoop, and plats E, F, G, and H were picked by hand. The first four
plats included vines of the Howe variety and the last four, vines of
the McFarlin variety, all of which had reached the age of normal
bearing.
TIME AND NUMBER OF APPLICATIONS.
The first three applications were made at practically the same time
for ail plats, since the growth of the two varieties on these: plats was
very much the same. The first application was made on May 2 to 6,
about the time when the largest number of buds were pushing forth
but had not exceeded a growth of approximately three-fourths of an
inch. This was the time when the young larve were appearing in
very large numbers but before many of them had got beyond reach of
the spray. |
The second application was made May 20 and 21, when many blos-
soms were in the hook stage, and was timed so as to catch the next lot
of larve before they could conceal themselves in the new growth.
The third came June 13 to 17, when the vines were nearly in full
bloom. It was designed to kill any late-hatching larve of the first
generation which might have been injuring the blossoms and newly
forming berries.
Plats C, E, G, and H received a fourth application on July 9 and
10 at about the time many berries were already set. This applica-
tion was intended to kill any very late-hatching larve and the moths
which appeared on the bogs in largest numbers about this time.
THE BordDEAUX NOZZLE.
The Bordeaux nozzle is modeled so as to deliver a forceful, driving
spray in the shape of a fan. The nozzle is so arranged that the in-
tensity of the fan-shaped spray can be regulated as desired. In
THE BLACKHEAD FIREWORM OF CRANBERRY. 29
Fie. 12.—Bordeaux nozzle equipment used in spraying experimental plats: a, Nozzles
held to show delivery of fan-shaped spray on a horizontal plane; 0, nozzles held in
. proper position for delivering spray to vines.
80 BULLETIN 1032, U. S. DEPARTMENT OF AGRICULTURE.
spraying plats B and G with this type of nozzle, an effort was made
to hit on a nearly horizontal plane the underside of all the leaves, as
well as to penetrate the vines and wet thoroughly with the spray solu-
tion all parts of the uprights, including the tips, by directing a force-
ful stream of spray, as shown in figure 12 6. The main idea was to
wet the eggs and also to catch the young larve in their burrows on
the undersides of the lower leaves, as well as to wet any larve in the
tips at the time.
As will be observed in Table 4, three applications with this nozzle
_ on Howe vines in plat B at an average rate of 522 gallons per acre
resulted in a gain in yield of 34.18 bushels per acre over the un-
treated plat; 89.74 per cent of the berries examined from this plat
were free from injury by the fireworm. On the McFarlin vines in
plat G four applications at an average rate of 697 gallons per acre, -
with this type of nozzle, produced a gain of 153.81 bushels per acre
over the check and 91.97 per cent of the sample berries were free
from fireworm injury. The small yields of plats A and B were
due largely to the fact that since the vines in this section had been
very badly infested the previous season, they produced very scanty
bloom, and they also appeared to suffer more from frost on May 4, 5,
and 6 than the other plats.
THE Mist Nozz.e.
The mist nozzle used was of the eddy-chamber or whirlpool-disk
type. somewhat larger than the Vermorel and without the center-
cleaning punch of the latter. It is so constructed internally as to
throw a medium fine mist in the form of a hollow cone of spray
which, depending upon the pressure of the liquid, measures from 12
to 18 inches in diameter about a foot from the nozzle. The outfit,
as shown in figure 18, was made from galvanized iron pipe one-fourth
to three-eighths of an inch in diameter on which four nozzles were
placed 11 inches apart and the whole attached to the end of an ordi-
nary 8 or 10 foot bamboo spray pole. The first nozzle on the end was
set close to the pipe and each succeeding one was set 1 inch farther
away than the preceding so that all would be the same distance from
the vines when the rod was held by the operator in proper position
for spraying. :
The applications with this type of nozzle on plats A and H were
made with the primary idea of filling the terminal whorl! of old leaves
and the new unfolding leaves at the tip of the upright with the nico-
tine sulphate and soap solution. As will be seen in figure 13, this
spray was delivered on a more or less vertical plane, and no special
effort was made to hit the underside of the leaves, entire dependence
being placed on a thorough soaking of the tips of the uprights, which
was quickly and easily done with this type of nozzle.
THE BLACKHEAD FIREWORM OF CRANBERRY. 31
On the Howe vines in plat A, three applications, at an average rate
of 391 gallons per acre, with the mist nozzle produced a gain in yield
of 18.52 bushels per acre over the check; 89.35 per cent of the berries
picked from sample areas were free from fireworm injury. On the
other hand, the same type of nozzle used on McFarlin vines in plat
H, with four applications at the rate of 485 gallons per acre, produced
a gain over the untreated vines in this section of 349.23 bushels per
acre, 93.81 per cent of the berries examined being free from fireworm
injury.
Fig. 18.—Mist nozzle equipment used in spraying experimental plats.
THE Spray GUN.
The spray gun (fig. 14) comprises usually a very large nozzle of
the eddy-chamber type attached to a piece of tubing of varying length,
fitted with a device for regulating at will the size and volume of the
spray delivered through the nozzle. It is of larger capacity than the
ordinary mist nozzle of the eddy-chamber type and is intended to be
used only on power outfits where the pressure can be maintained at
200 pounds or over. ‘In these experiments this type of nozzle was used
at full-capacity opening with a medium-sized disk and threw a stream
of spray about 15 to 20 feet long, which broke up into a medium fine
mist before it reached the vines.
In the use of the spray gun on plats C, D, E, and F an effort was
made to fill the tips of the uprights with the spray liquid and also to
hit the undersides of the leaves by holding the nozzle close enough to
the vines so that the liquid would be delivered on a nearly horizontal
32 BULLETIN 1032, U. S. DEPARTMENT OF AGRICULTURE.
plane. In this position the uprights would be bent over slightly and
the tips as well as some of the lower leaves given a thorough wetting.
As seen in Table 4, three applications with this type of nozzle on
the Howe variety (plat D) resulted in an increase of 58.95 bushels
per acre over check, and 84.25 per cent of the berries examined were
free from fireworm injury. Four applications on the same variety
on the adjoining plat (plat C) resulted in a gain in yield of only
40.88 bushels over the check, doubtless because of the thin setting of ©
blossoms on this plat, but 93.05 per cent of the fruit examined from
the sample areas was free from fireworm injury.
Fig, 14.—Spray-gun used in spraying experimental plats. Shows size of stream of spray
used, with medium-sized disk at full capacity.
On the McFarlin variety (plat F) three applications gave a gain of
109.62 bushels per acre over the untreated vines, 77.45 per cent of the
examined fruit being free from fireworm injury. Four applications
(plat E) gave better results, a gain of 161.85 bushels over the un-
treated vines, 87.72 per cent of the examined fruit being sound.
THE THREE TYPES OF NOZZLES COMPARED AS TO ECONOMY OF TIME AND MATERIAL.
With the Bordeaux outfit (fig. 12) it took about 1} hours to spray
an acre, an average of 609 gallons being necessary for a thorough
application. It was necessary to walk about 24 times across the
acre, which was in the form of a square. With the mist outfit
(fig. 18), it took about 1 hour to spray an acre, 438 being the average
THE BLACKHEAD FIREWORM OF CRANBERRY. 88
number of gallons used for a thorough application. Approximately
12 trips were necessary across an acre with this outfit. In point of
time and material the spray gun was the most economical, requiring
only 35 or 40 minutes to spray an acre, with an average of 375 gallons
for an application. It was necessary to make only 6 to 8 trips with one
spray gun across an acre. :
- EFFECT OF THE NICOTINE-SULPHATE-AND-SOAP SOLUTION ON THE CRANBERRY PLANT.
Although 40 per cent nicotine sulphate in the proportion of 1 part
to 800 parts of water with fish-oil soap at the rate of 2 pounds to
each 50 gallons of solution was apphed to the vines when they were
almost in full bloom, no decided decrease in the setting and maturity
of the berries seemed to occur on those plats on which the spray
was not applied forcefully or on a nearly horizontal plane. It will
be noted, however, in Table 4 that the percentage of unfertilized and
immature berries, 1.-e., the very small, dried, and undeveloped ones,
but which were free from fireworm injury, was slightly, and in some
cases considerably, increased in all the sprayed plats except F as
compared with the respective untreated ones, the three plats with the
highest percentage of berries of this kind being plats B, C, and G.
Some explanation of this may possibly be found in the fact that in
_ two of these plats, namely, B and G, the spray was applied forcefully
with the Bordeaux nozzle on a nearly horizontal plane, which prob-
ably could have seriously affected the fertility of the blossoms, as in
some cases they were almost blown from the uprights. Plat C re-
ceived four rather forceful applications with the spray gun, and this
also may in a measure account for the high percentage of unfertilized
berries picked from this plat.
It is generally recognized among cranberry growers and others
familiar with cranberry culture that the presence of a large amount
of wet weather during the blooming period sometimes results in a
small crop of berries. Whether or not the wet weather causes a de-
creased crop by preventing the ordinary pollenization by insects or
by destroying the fertility of some blossoms still seems to be a matter
of conjecture. Since all the plats were affected by the same set of
natural conditions, however, it would seem logical to suppose that
the spraying of the vines while the blossoms were open with a type
of nozzle which delivered a forceful spray on a more or less hori-
zontal plane, and which thus thoroughly wet the floral organs, might
have caused the comparatively small crop on the plats thus treated,
by the sterilization and mechanical destruction of the blossoms.
On the other hand, a certain rather beneficial effect in addition to
the control of the fireworm was observed from the use of the nicotine-
-sulphate-and-soap solution, especially on the McFarlin variety. On
34 BULLETIN 1032, U. S. DEPARTMENT OF AGRICULTURE.
plats E, F, G, and H, but particularly on H, it was noticed that the
berries were generally much larger and the vines of a brighter green
than those on the other plats. Wherever this spray solution was used
it seemed to have a fertilizing or stimulating effect on the vines,
making them grow more luxuriantly and produce larger sized berries
than they otherwise would have done.
RECOMMENDATIONS FOR CONTROL.
REFLOWING.
As recommended by Scammel,'* reflowing, where it is possible to
do it properly, will doubtless be as effective in controlling the black-
head fireworm on the Pacific coast as elsewhere. While no experi-
ments were performed along this line on the Pacific coast, yet for the
benefit of those growers who may be able to equip their bogs for
reflowing and wish to employ this method of control, it might be
stated that the proper time to reflow for the fireworm is when the
majority of the larve of the first brood are about full grown, as at
this time they can be more easily and quickly killed than in any other
stage.* On the bogs in the vicinity of Seaview, Wash., the majority
of the larvee of the first brood are full grown near the middle or
latter part of May, but if the bog is winter flowed, i. e., covered
with water in the wintertime, this date would vary according to
the date this winter flood was drawn from the bog. In reflowing, the —
water should completely cover the vines and be held there for at least
48 hours in order to kill the greatest number of larve. Any grass or
other objects projecting above the surface should be removed so that
the larvee can not crawl up to the tops and thus escape the flood.
SPRAYING.
Spraying with a solution of 40 per cent nicotine sulphate and
water, with soap as a spreader, has been found to be the most effec-
tive method of controlling the blackhead fireworm on the Pacific
coast.
How To PREPARE THE NICOTINE SULPHATE SPRAY.
Any nicotine solution containing 40 per cent of nicotine sulphate
is suitable in the preparation of this spray, and any kind of soap
free from uncombined oils or greases may be used as a spreader.
The proportions found most effective against the fireworm are: One
part of 40 per cent nicotine sulphate to 800 parts of water, with 2
pounds of soap to each 50 gallons of the liquid. Solutions containing
a greater proportion of nicotine sulphate than 1 to 800 will do no
% Scammel, H. B. Cranberry Insect Problems and Suggestions for Solving Them.
U. S. Dept. of Agr., Farmers’ Bulletin 860, p. 7-8. 1917.
14 Ibid, p. 8.
THE BLACKHEAD FIREWORM OF CRANBERRY, 3)
harm, but on the other hand will give no better control, and if used
at the rate of 1 part to 1,000 parts of water with the above proportion
of soap, about one-third to one-half more gallons per acre should be
used and then only on light infestations.
To make 200 gallons of this material the tank should be run
about three-fourths full of water while washing through the sieve
8 pounds of the soap, which should be previously broken up in warm
water or otherwise thoroughly softened. One quart of the 40 per cent
nicotine sulphate should then be poured slowly into the tank with the
remainder of the water necessary to make up the 200 gallons while
the whole solution is being thoroughly agitated to insure proper mix-
ing of the ingredients. It is then ready to be applied to the vines.
The nicotine sulphate is added last and in a diluted form to pre-
vent the precipitate which forms when concentrated solutions of
nicotine sulphate and soap are brought together and which decreases
the effectiveness of the spray solution.
If these materials are to be combined with Bordeaux mixture, the
proportions of nicotine sulphate and soap and the process of mixing
is the same as though water were used to make the solution as
described above. Nicotine sulphate can be mixed with lime-sul-
phur solutions in all the usual proportions, but no soap should
be added to a solution containing lime-sulphur or any other similar
compound, else a disintegration of the ingredients will take place
which will not only weaken the effectiveness of the combination but
also may cause severe injury to the cranberry vines.
THE AMOUNT TO BE USED PER ACRE.
Depending on the severity of the infestation, not less than 250 to
300 gallons of this solution should be used in spraying an acre of
vines, as good control can not usually be secured with a less amount
than this. If it is preferred to use 40 per cent nicotine sulphate at
the rate of 1 to 1,000, rather heavy applications will have to be made,
less than 400 or 500 gallons per acre never being used.
TYPE OF NOZZLE.
The use of a nozzle, preferably of the large eddy-chamber type
shown in figure 18, equipped with a disk, throwing a medium-fine
mist which will quickly and easily wet the terminal whorl of leaves
on the tip of the uprights, is to be recommended. The Vermorel
type of nozzle is too small and throws too fine a mist (fig. 15), most
of which is driven away by the wind and thus fails to give the de-
sired results. The spray gun should be used only on very large and
thinly infested bogs and then great care must be taken to see that no
- uprights are missed and that a uniform application is made with
the pressure at the tank never less than 200 pounds per square inch.
36. BULLETIN 1032, U. S. DEPARTMENT OF AGRICULTURE.
PRESSURE.
~
The pressure need not be higher than about 200 or 250 pounds at
the tank, depending upon the size and length of pipe or hose through
which the liquid has to be forced and the number and kind of noz-
zles used.
Tre ‘AND NUMBER OF APPLICATIONS.
For vines which are only lightly infested three applications are
recommended. The fivst of these should come when the new upright
growth is from one-half to three-fourths of an inch long; that is,
Fic. 15.—A spray boom for holding 10 Vermorel nozzles. Note the unevenness of the
Spray cone and the necessity of considerable walking and dragging of hose over vines
in spraying. Not a good type of outfit to use.
when large numbers of the young larve are proceeding to and some
working in or near the new unfolding leaves at the tips of the up-
rights. The second should be applied shortly after the first blos-
soms appear, or, in other words, at the early “hook stage.” This
may come from 10 days to 3 weeks after the first application, de-
pending on the weather; it is designed to kill the next group of
larvee before they conceal themselves in the new growth. The third
application should be made when the vines are in full bloom, or
about 2 weeks after the second application, the object being to keep
the young larvee from destroying blossoms and newly forming berries.
¢
THE BLACKHEAD FIREWORM OF CRANBERRY. 37
Vines which are rather heavily infested will require the first year
all three applications, as outlined above, and an additional fourth |
application, which should be made during the first two weeks of
July. This last spray is designed to give protection, both to the
berries and to the upright tips in which the fruit buds for the fol-
lowing year’s crop are forming, against late hatching larve of the
first generation and the first Meee of the second generation. It is
also designed to kill many of the moths of the fet generation, and
it should, therefore, be timed so as to come within the limits men-
tioned, as it is about this time that the moths are flying in largest
numbers. By careful spraying with an outfit like that shown in fig-
ure 13, one application at this time will clean a bog of fireworm moths
-and thus prevent a large number of the eggs of the second generation
from being deposited.
KIND OF EQUIPMENT.
A 50-gallon wheel-barrel outfit, with a strong pump, will usually
be found sufficiently large for bogs up to several acres in extent. For
larger bogs the power outfits of various sizes will be most economical,
and in order to avoid dangerous delays at spraying time one should
be sure that the parts are not only durable but easily AOEESSIOS and
replaceable as well.
Any arrangement of nozzles and manner of spraying the ee that
will insure thorough application of the spray as previously outlined
and at the same time cause a minimum injury to the vines from walk-
ing or dragging the hose over them will be satisfactory.
After a consideration of the factors which influence the hatching
and development of the blackhead fireworm (see pages 8-9), it would
seem reasonable to suppose that a covering of water held over the
vines until late in the spring, say until about April 10 to 15, together
with the thinning out of thickly vined bogs, would have a very bene-
ficial effect. It would also facilitate good control work by grouping
the hatching of the larve. In view of the fact that it is also con-
sidered a good horticultural practice on the Pacific coast, this method
of bog management in connection with spraying is to be reeommended
wherever it is practicable, especially on bogs which are badly in-
fested with fireworms.
SUMMARY AND CONCLUSIONS.
The blackhead fireworm (/?hopobota naevana Hiibner) is the most
important pest of the cranberry on Pacific coast bogs. It is found
also on native cranberry vines well isolated from cultivated bogs,
but was doubtless introduced on these cultivated bogs on cuttings
from eastern cranberry districts. So far as known on the Pacific
coast, it feeds only on the cranberry.
38 BULLETIN 1032, U. S. DEPARTMENT OF AGRICULTURE.
The phenology of the cranberry in that locality is quite vari-
able. Usually on the earliest varieties, such as the McFarlin and
Early Black, buds begin to break and the new growth begins to
push forth about the beginning of April. The new upright growth
is about three-fourths of an inch long by the middle of April, the
blossoms are in the “hook stage” in about a month more, and full
bloom comes about the beginning of June. The late varieties, such as
the Howe, are more variable, but the new growth starts the beginning
of May and attains three-fourths of an inch in about a week. The
majority of the blossoms are in the “ hook stage” about the middle of
June and fully opened by the latter part of June or earty July.
Almost none of the bogs on the Pacific coast are ever completely
covered with water, and the seasonal temperature is comparatively
equable. These conditions, coupled with the small number of para-
sites, enable this pest to be very destructive, the larve feeding on
the buds, foliage, blossoms, and fruit throughout the growing season.
The insect passes the winter in the egg stage. The eggs are quite
small, smooth, and shghtly oval, with the center slightly raised or
rounded. They are lemon and orange yellow and are deposited singly
or in small irregular groups on the undersides of the cranberry leaves.
The young larva on hatching leaves the egg through a rent near the
edge of the upper side and then feeds for a few days on the leaf or
leaves near by. Later it proceeds to the tip of the upright, there
feeding on the unfolding buds and blossoms.
By rearing the insect from the egg stage in an outdoor shelter
where conditions were maintained which approached those natu-
rally found on the cranberry bog, it was found that there are annually
two full generations and sometimes a partial third. Temperature,
depth of vines, and drainage are the three most important factors
in the hatching and development of the fireworm.
The mature larva is very active, is about one-fourth of an inch
long, dark greenish yellow, with a coat of dark olive-green above,
and with head and thoracic shield varying from light brown to
black. The ravages of the larve result in a burnt appearance of the
vines, as if a fire had swept over the bog. Hence the common name
“blackhead fireworm.”
Nearly ail the larve change to pupe in loosely constructed cocoons
in old leaves and trash beneath the vines. The pupa is a little less
than one-fourth of an inch long and of a brownish amber color.
The adult or moth moves in quick, jerky flights, is about the same
length as the mature larva, and has characteristic markings of a single
row of short, alternating brownish and silver-gray bars running
diagonally to the front margin of the first pair of wings. The males
have an irregular dark area near the front margin on the underside
of the second or lower pair of wings.
THE BLACKHEAD FIREWORM OF CRANBERRY. 39
Naturally the moths do not migrate more than a few yards, but,
helped by a strong wind, it is possible for them to be carried as far
as several hundred feet at a flight. In the egg stage, the fireworm
can be disseminated over a bog in two other ways—namely, on leaves
floating on the water which naturally gathers on the bog in the
winter time and on leaves on cuttings used in planting.
Egg laying usually commences from one to several days after copu-
lation and closely follows the temperature, the largest number being
deposited between 3 and 9 p. m.
The larve of the first generation appear on the bogs in greatest
abundance about the latter part of May, the pupe toward the middle
of June, and the moths about the first or second week in July.
A fungous disease which attacks the pupe in their cocoons in the
old leaves beneath the vines is responsible for the death of a large
number, especially on old and badly infested bogs. Spiders and
ladybird beetles also kill a large number of the fireworm moths and
larvee.
Control experiments seeking to establish the best kind of spray
materials, the proper number of applications, and the most effective
manner of applying them, were conducted on small and large scales
under natural bog conditions. Forty per cent nicotine sulphate at
the rate of 1 part to 800 parts of water, with the addition of fish-oil
soap at the rate of 2 pounds to every 50 gallons, used at the rate of
about 300 gallons to the acre, was found to be the most effective spray
material against the fireworm. Forty per cent nicotine sulphate,
used at the rate of 1 part to 1,000 parts of water with the addition
of fish-oil soap, 2 pounds to every 50 gallons, was nearly as effective.
Nicotine oleate made by mixing 2} parts of a solution containing
40 per cent free nicotine with 1} parts of commercial oleic acid, or
red oil, and used at the rate of 1 part to 400 parts of water, applied
three times at the rate of about 300 to 400 gallons per acre, was found
nearly as effective as 40 per cent nicotine sulphate 1 to 800 with fish-
oil soap 2 to 50, apphed three times at the minimum rate per acre.
Arsenate of lead proved of little or no value in the control of the
fireworm. Fish-oil soap, 2 pounds to 50 gallons of solution, was a
much better spreader for spray solutions on cranberry foliage than
glue, which was used at the rate of 1 pound to 200 gallons. One com-
pound containing a high percentage of crude carbolic acid and usually
employed as a disinfectant gave little or no control.
Demonstration spraying experiments were conducted in which 40
per cent nicotine sulphate 1 to 800, with fish-oil soap 2 pounds to 50
gallons, was used. Four applications on McFarlin vines, in which
the eddy-chamber mist type of nozzle was used, gave the best results,
producing the largest yield of berries and the highest percentage of
berries free from fireworm injury. -
40 BULLETIN 1032, U. S. DEPARTMENT OF AGRICULTURE.
The spray gun, used in spraying McFarlin vines four times, gave
the next highest yield, but the third highest percentage of uninfested
fruit of this variety.
The results of four applications with the Bordeaux type of nozzle
on the McFarlin variety ranked third in yield and second in per-
centage of uninfested McFarlin berries.
No very definite conclusions based on yield can be drawn from the
experiments of spraying on the Howe variety on account of injury by
the fireworm on the plats in 1918 and frost in the spring of 1919. Of
the Howe plats receiving three applications, however, the one sprayed
with the Bordeaux type of nozzle resulted in the highest percentage
of fruit free from fireworm injury, that sprayed with the mist type
of nozzle was second, and that with the spray gun was third.
Four applications with the spray gun on the Howe variety gave the
highest percentage of uninfested fruit of all the plats on which the
spray gun was used.
Generally speaking, four applications gave better results than three.
On bogs that can be reflowed, a complete covering of the vines with
water for not less than 48 hours during the middle or latter part of
May is recommended as a help in the control of the fireworm. Since
most of the bogs on the Pacific coast, however, are managed as dry
bogs, spraying with 40 per cent nicotine sulphate 1 to 800, with the
addition of fish-oil soap at the rate of 2 pounds to every 50 gallons,
is recommended as the most feasible method of control of the black-
head fireworm in that locality.
Between 250 and 300 gallons of this material should be used per
acre. In making up the nicotine sulphate spray, the fish-oil soap
should be mixed with about half the quantity of water and the re-
quired amount of nicotine sulphate added with the remainder of the
water to prevent the formation of a precipitate which decreases the
effectiveness of the spray solution and which might also clog the
nozzles and possibly injure the vines. This spray solution can be com-
bined with Bordeaux mixture or lime-sulphur in the usual propor-
tions, in which case the process of mixing is the same as though water
were used. Vo soap, however, should be added if the mixture contains
lime-sulphur. The large eddy-chamber type of nozzle, throwing a
medium fine mist, at a pressure of about 200 pounds at the tank, should
be used; other types of nozzles may not only give unsatisfactory re-
sults but may also injure the blossoms. The spray gun should be em-
ployed only on lightly infested bogs.
Vines which are lightly infested should have three applications of
the nicotine sulphate spray, the first one when the new upright growth
has reached a length of about three-fourths of an inch, the second
when the blossoms are in the early “ hook stage,” and the third when
the vines are in full bloom.
THE BLACKHEAD FIREWORM OF CRANBERRY. 4]
Heavily infested vines should have all of these three applications
at the times mentioned and an additional fourth application during
the first two weeks of July. In the application of this last spray an
effort should be made to hit as many moths as possible with the spray
solution.
A 50-gallon barrel outfit on wheels, with a strong pump, will be
found desirable for small bogs. For bogs larger than several acres in
area, power outfits should be used.
In making the applications great care should always be exercised
to prevent injury to the vines.
SYSTEMATIC DESCRIPTION OF RHOPOBOTA NAEVANA HUBNER.
By Cart HEtnricH, Bureau of Hntomology.
SYNONYMY. S
Tortrix naevana Hiibner, in Samm. Eur. Schmett., v. 5, Tort., pl. 41,
fig. 261, 1814.
Tortrix unipunctana Haworth, in Lep. Brit., p. 454, 1812.
Lithographia geminana Stephens, in List Brit. Mus., Pt. X, Lep., p. 99,
1852.
? Sciaphila luctiferana Walker, in Cat. Brit. Mus., Lep., ser. 6, pt. 28,
p. 342, 1863.
Anchylopera vacciniana Packard, in Guide Stud. Ins., p. 338, 1869.
Rhopobota naevana Staudinger and Rebel, in Cat. Lepidop., aufl. 3,
theil 2, p. 127, 1901.
Eudemis vacciniana Dyar, in List No. Amer. Lepidop., p. 466, no. 5238,
1902.
Rhopobota naevana Dampf, in Iris, bd. 21, p. 304-329, 1908.
GENERAL CHARACTERS.
ADULT.
Plate I, A; Plate II, A, B, C.
Thorax smooth. Forewing smooth; termen deeply concaved between veins
4 and 6; apex pointed but not faleate; 12 veins; 7 and 8 stalked; 10 from cell
midway between 9 and 11; 9 approximate to 8; 11 from cell at or just before
middle of cell; upper internal vein of cell nearly obsolete, when distinguishable,
from between 9 and 10; 3, 4, and 5 closely approximate at termen; 2 bent up
slightly at outer third; costal fold in male absent. Hindwing with 8 veins;
6 and 7 approximate toward base; 3 and 4 stalked; male with a shading of
coarse black scales on underside of wing along upper vein of cell. Male
genitalia as figured; harpes undivided, with rudimentary clasper present and
on outer surface just above lower margin a row of rather long, stout spines;
uncus present, bifurcate, arms widely separated, rather short, weakly chitinized
and slipper shaped; gnathos reduced and fusing with socii; socii greatly
developed, porrected, extremities meeting in hairy knoblike projection;
aedoeagus straight, moderately long, fairly stout.
PUPA.
Plate, B,.C-
-
Slender, abdominal segments gradually tapering; a double row of spines on
dorsum of abdominal segments 38 to 6 inclusive, a single row on abdominal
segments 2, 7, 8. 9, and 10; first abdominal segment smooth; wings extending
to or slightly beyond ventro-caudal margin of fourth abdominal segment;
cephalic end bluntly rounded; vertex distinct, as broad as prothorax; labrum,
mandibles, and maxillary palpi well developed; maxillary palpi extending to
proximo-lateral angles of maxille; maxille less than half the wing length;
labial palpi half the length of maxillze; prothoracic femora and mesothoracic
42
€
THE BLACKHEAD FIREWORM OF CRANBERRY. 43
coxe exposed; antennz and mesothoracic legs not reaching to end of wings;
several strong setze on tenth abdominal segment; a pair of stout setz on each
side of anal rise; anal rise unarmed; body sete otherwise weak and hardly
distinguishable; spiracles slightly reduced; anal and genital openings slitlike
in both sexes; cremaster absent.
LARVA.
Plate il. i UPteite done wA@) HC
Cylindrical, slender, very slightly tapering at caudal end. No secondary hair.
Legs and prolegs normal. Crochets uniordinal, in a complete circle. Anal
fork present, reduced. Prothoracic shield broad, divided. Spiracles round,
moderate; that on eighth abdominal segment slightly higher than those on
abdominal segments 1 to 7, not over one and one-half times as large, same size
as that on prothorax. Skin evenly and appreciably scobinate.
Body sete moderately long; tubercles broadly chit’nized; IV and V on
abdominal segments 1 to 8 under the spiracle and approximate; prespiracular
shield of prothorax elongate, large, bearing three sete (III, IV, and V) ina
longitudinal line; group VI bisetose on prothorax, unisetoSse on mesothorax
and metathorax, greatly reduced and closely approximate to IV and V on
abdominal segment 9; III antero-ventrad of the spiracle on eighth abdominal
segment, directly over the spiracle on abdominal segments 1 to 7; I1la not distin-
guishable ; on thoracic segments 6 setz in group VII; VII bisetose on abdominal
segments 7, 8, and 9; ninth abdominal segment with 9 sete in a nearly vertical
line, paired sete of group II close together on same chitinization on dorsum,
I and III closely approximate; on abdominal segments 1 to 8 IT latero-caudad
of I; prothorax with II* slightly higher than I*, closer to II” than to I*, II?
above the level of puncture z; I? nearer te puncture z than to I°, II° about equi-
distant from I° and I°, puncture y directly caudad of I*, puncture x dorso-
eaudad of I@ and on the level of IT@.
Head capsule spherical, nearly square in outline viewed from above; slightly
wider than long; greatest width well back of middle of head; incision of
dorsal hind margin slight, about one-fourth the width of the head’ distance
between dorsal extremities of hind margin about half the width of the head.
Frons broad, triangular, longer than wide, reaching beyond middle of the head.
Adfrontal sutures extending to incision of dorsal hind margin. Longitudinal
ridge very short, less than one-third the length of the frons.
Ocelli six; lenses well defined.
Epistoma normal.
Frontal punctures close together; well forward of frontal setze; distance
from frontal seta (E") to first adfrontal seta (Adf*) about equal to distance
separating adfrontal sete (Adf and Adf’) ; Adf? anterior to beginning of longi-
tudinal ridge; puncture Adf* between and about equidistant from Adf* and
Adf’.
Hpicranium with the normal primary setz and punctures and with a row
of three ultraposterior sete and one puncture. Anterior sete (A’, A?, and A‘)
in a line with lateral sets (1*); anterior puncture (A*) closely approximate
to and posterodorsad of A. Posterior sete (P’ and P’) and puncture (P”)
in a line with first adfrontal seta (Adf'); P* about middle of head, on the
level of adfrontal puncture and lateral seta (L*); P” between and about equi-
distant from P* and P’; puncture P* lying between P* and L’, approximate to
the latter. Lateral puncture directly posterior to L’, remote. Ocellar setz
(O71, O?, O°) well separated, forming a right angle; O° lying below and between
ocelli II and III; 0? postero-ventrad of ocellus I, in a line with ocelli 1 and II
44 BULLETIN 1032, U. S. DEPARTMENT OF AGRICULTURE.
and seta A*; O* ventrad of 0’, remote; ocellar puncture not distinguishable.
Subocellar sete (SO’*, SO’, and SO*) triangularly placed; puncture SO’ ap-
proximate to and equidistant from SO’ and SO*. Genal puncture (G*) anterior
to the seta (G*).
Labrum with median incision broadly triangular, rather shallow; median
setzee (M'*, M’, M*) triangularly placed; M’ postero-laterad of M* and closer to
M’* than to M*; La’ directly posterior of and approximate to La?, behind the
level of M’; La’ on the level of M*; La® and M® on the same level near anterior
margin of labrum; puncture approximate and posterior to M’.
Epipharyngeal shield narrowly bordering the median incision, not sharply
defined. Epipharyngeal setz triangularly grouped, rather close together, nar-
row, moderately long. Epipharyngeal rods indicated only by their short posterior
projections.
Hees.
Plate III, D.
Oval, flat, scale-like, iridescent; deposited singly.
e SPECIFIC DESCRIPTION.
ADULT.
Palpi brownish on outer sides, grayish white on inner and upper sides. Face
and head grayish, more or less suffused with fuscous. Thorax fuscous. Fore-
wings grayish, cross-marked with fuscous or, in some specimens, dark reddish
brown; the brown area forming an outwardly angulated basal patch some-
what marked with gray or whitish scales and covering the basal third of the
wing; a similar brown suffusion forming an ill-defined fascia extending from
just beyond middle of costa to tornus, considerably wider on dorsum than on
costa; a narrow brown terminal line, following .the contour of termen and
broadening at apex to a distinct brown spot; a fainter angulate brown line
from costa dividing the ocellus; on costa six or seven pairs of short, somewhat
obscure, white geminate marks separated by distinctly brownish shadings;
ocellus metallic gray with longitudinal markings. Hindwings fuscous. Legs
fuscous with inner sides white or grayish and tarsi annulated with white.
Alar expanse, 9-14 mm.
PUPA.
Length, 5-6 mm.; yellow or yellowish brown, not appreciably darker
at extremities but with sutures and caudal margins of abdominal segments
brown; dorsal abdominal spines brown, arranged as shown in Plate I, C.
LARVA.
When full grown, 10-11 mm. long by 1 mm. broad. Body sordid white;
the scobination blackish, giving the entire larva a pale smoky fuscous color;
chitinized areas about body tubercles white except on prothorax where they are
dark brown, in some specimens almost black; thoracic shield brown or blackish
brown; median dividing line pale yellow; chitinized parts of thoracic legs
black or blackish brown; anal shield yellowish; anal fork two-pronged, small
and easily overlooked ; body hairs brown; crochets 36-42, brown, weaker at the
cephalic end of the circle and increasing in length toward the caudal margin
where the longest are over twice as long as the shortest at the anterior margin
(Pl. III, ©). Head yellow, more or less suffused with dark brown, especially
on ventral side; a distinct brownish patch at posterior lateral angle of epi-
cranium; chitinized parts of trophi black or blackish brown; ocellar pigment
black, continuous under the ocelli; lenses white.
THE BLACKHEAD FIREWORM OF CRANBERRY. 45
Hee.
Shining grayish white; entire surface finely and evenly faceted, smooth.
This species has appeared in our economic literature and lists under
the name vacciniena Packard, and has been held to be an American
species distinct from the European naevana Hiibner, although the
synonymy has been long suspected. A careful comparison of the
genitalia and external characters of the two shows them to be one
species. Another American species, /'pinotia ilicifoliana Kearfott,
also should be referred to the genus Rhopobota as a variety of
FR. naevana. In genitalia it is identical but differs somewhat in pat-
tern. Dampf, in a very excellent study of their genitalia, has shown
the synonymy of the two European forms naevana Hiibner and
geminana Stephens.
The larva of Rhopobota naevana is easily confused with another
cranberry feeder, Peronea minuta Robinson, which it superficially re-
sembles. The latter, however, can be at once distinguished by the ar-
rangement of setz I, IJ, and III on the ninth abdominal segment and
its different anal fork. In &. naevana I and III are closely approxi-
mated and on a single chitinization and the anal fork is two-pronged
and very small; whereas in P. ménuta I is well separated from ITI,
about equidistant from both IT and II, and both I and III are on
separate chitinizations and the anal fork is five or six pronged, large,
and rather conspicuous.
EXPLANATION OF PLATES.
Prank
Rhopobota naevana:
A.—Adult. C.—Pupa, dorsal view.
B.—Pupa, ventral view.
Explanation of symbols applied to pupa.
a = antenna. 1* = metathoracie leg.
ao = anal opening. Ip = labial palpi.
at = invaginations for anterior md = mandible.
arms of tentorium. mp = maxillary palpus.
cx’ = coxa of mesothoracic leg. ms = mesothorax.
es = epicranial suture. mt = metathorax.
f' = femur of prothoracic leg. mx = maxilla.
ge = glazed eyepiece. p = prothorax.
go = genital opening. se = sculptured eyepiece.
lb = labrum. v = vertex.
I’ = prothoracie leg. 1 to 10 = abdominal segments i to 10.
1? = mesothoracic leg.
Pravte TI.
Rhopobota naevana:
A.—Denuded forewing of female moth, showing venation.
B.—Denuded hindwing of female moth, showing venation.
C.—Male genitalia of moth: ventral view of organs spread.
D.—Setal map of first and second thoracic, and third, eighth, and ninth abdomi-
nal segments of larva, showing arrangement of body sete.
46 BULLETIN 1032, U. S. DEPARTMENT OF AGRICULTURE.
Explanation of symbols applied to genitalia.
Ae = eedeeagus. Hp = harpe.
An = anellus. Si = socii.
Cl = clasper.. ~ U = uncus.
Cn = cornuti (spines on penis). Vm = vinculum.
Gn = gnathos.
PLATS TPE
Rhopobota naevana:
A.—Dorsal view of head capsule of larva, showing setal arrangement.
B.—Lateral view of head capsule of larva, showing setal arrangement.
C.— Arrangement of crochets of abdominal proleg of larva.
D.— Egg, greatly magnified.
E—Ventral view of tenth abdominal segment of larva, showing anal fork.
F.—Labrum of larva.
G.—Epipharynx of larva.
Explanation of symbols applied to larva.
At, A’, A®, A*=setee and puncture of anterior group of epicranium.
Adf, Adf*, Adf@—=adfrontal setze and puncture of epicranium.
ADFR=adfrontal ridge of larval head.
ADFS=adfrontal suture of larval head.
Af=anal fork.
E’, E’=epistomal setze.
ER=epipharyngeal rod.
ES>epipharyngeal shield.
ET=epipharyngeal sete.
F’, F*=frontal seta and puncture of epicranium.
FR=fTrons of epicranium.
G*, G*=genal seta and puncture of epicranium.
L’, L?=seta and puncture of lateral group of evicranium.
La’, La’. La*=lateral sete of labrum.
Lp=labral puncture.
LR=longitudinal ridge of epicranium.
M’*, M’*, \’=median setze of labrum.
O*, 0’, O°=setze of ocellar group of epicranium.
Pp’, P*, P*, P°=setz and punctures of posterior group of epicranium.
SO*, SO”, SO*, SO?=setz and puncture of subocellar group of epicranium.
X=—=ultraposterior sete and puncture of epicranium.
Drawings on Plates I, II (except C), and ITI were made under the author’s
supervision by Miss E. Edmonston, of the Bureau of Entomology. The male
genitalia (Pl. II, C) were drawn by Miss Ada F. Kneale, formerly of the Bu-
reau of Entomology.
Bul, 1032, U. S. Dept. of Agriculture, PATE I:
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THE BLACKHEAD FIREWORM OF CRANBERRY.
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Bul, 1032, U. S. Dept. of Agriculture.
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THE BLACKHEAD FIREWORM OF CRANBERRY.
Bul. 1032, U. S. Dept. of Agriculture.
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THE BLACKHEAD FIREWORM OF CRANBERRY.
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