ateed

oss

me

seein aia
bie Ss idese,

elie ay gid
x

e Mr ee
Coo Ci
<

Soke Pee pty fg fun fh wwe ee
Bag ticd carraee

VAT ELL tee
wb idadede, a) f.

mbes Ed ror rot

af .
at ta be ho 8 0

AI URAL HISTORY

i

SURVEY

STATE OF ILLINOIS
DEPARTMENT OF REGISTRATION AND EDUCATION

SYSTEMIC INSECTICIDE CONTROL OF
SOME PESTS OF TREES AND SHRUBS —
A PRELIMINARY REPORT

L. L. ENGLISH
WALTER HARTSTIRN

al, ;
~~ ts \
ee?

Biological Notes No. 48
: August, 1962

NATURAL HISTORY SURVEY DIVISION

:
| Urbana, Illinois
|
|

Fig. 1. — Application of SD-3562 to the uninjured bark of Fig. 2. — Injection of SD-3562 into the soil.
a honey locust tree. A measured dosage of the chemical is A bucket pump and wand are used to inject diluted
applied with a syringe. SD-3562 into the soil around a plant. The plastic
bag covering the piston is a safety device to

Cover photograph shows mimosa webworm on honey locust. protect the pump operator from the chemical.

Fig. 3. — Method of injecting SD-3562 into drilled holes in tree. C

Diagrammatic presentation b shows approximate downward tilt of a drilled hole in a tree and position of syringe at time
of injection of SD-3562.

ross section a shows arrangement of drilled holes.

SYSTEMIC INSECTICIDE CONTROL OF SOME PESTS
OF TREES AND SHRUBS—A PRELIMINARY REPORT

Information supplied by entomologists of the Shell
Development Company of Modesto, California, in the
spring of 1959, indicated the possibility of controlling
the smaller European elm bark beetle, Scolytus multi-
striatus (Marsham), on elms by injectinga new chemical,
SD-3562, into the trees, fig. 3. The beetle is well
known as the principal vector of the Dutch elm disease.
Later developments suggested the possibility of con-
trolling other pests of trees and shrubs with bark or
soil applications of SD-3562, figs. land 2. This chemi-
cal, an organic compound, 3-(dimethoxyphosphinyloxy)-
N,N-dimethyl-cis-crotonamide, is a systemic insecticide.
When taken up by a plant, it is translocated to the
stems and leaves, making the plant poisonous to insects
that feed on it.

Technical grade SD-3562, used in the experiments
reported in this paper, is a brown liquid with a mild
odor. It is water soluble and is highly toxic to warm-
blooded animals as well as insects. In the research
reported here, the chemical was used undiluted except
when placed in the soil around trees or shrubs.

The insecticidal activity of technical SD-3562 is
proportional to the amount of alpha isomer (actual
SD-3562) in the solution. Early preparations, with only
30 to 50 per cent alpha isomer, were used in our experi-
ments of 1959 and 1960. Improved manufacturing pro-
cesses made possible an increase in the alpha isomer
to 75 per cent. The preparation with the higher concen-
tration of alpha isomer was used in the experiments
we performed in 1961. At the time of publication of
this paper, SD-3562 is not available for use by the
public.

PHYTOTOXICITY TESTS

Before tests were undertaken with insects,
phytotoxicity tests with SD-3562 were conducted on
American elm trees in a nursery plot at Urbana-
Champaign. The trees, about 3 inches in diameter at
breast height (dbh), were treated on June 19, 1959, with
technical SD-3562 at rates of 0.5, 1, 2, 4, and 8 ml per
inch of tree dbh. The undiluted chemical was measured
with a syringe and placed in holesthree-eighthsinch in
diameter bored at a downward angle into the trunk of
each tree at about 3 feet above the ground, fig. 3. In

*L. L. English is Entomologist and Walter Hartstirn isAssistant
Plant Pathologist, Illinois Natural History Survey. Robert Snetsinger,
Robert Kukla, and Clifford Scherer assisted with the work reported
here. Howard W. Fox, Forester of Sinnissippi Forest, and Noel B.
Wysong, Chief Forester, Forest Preserve District of Cook County,
co-operated in the field tests. Wilmer Zehr took the photographs.
Mrs. Anne R. Dreyfuss and James S. Ayars edited the manuscript.

This paper is printed by authority of the State of Illinois, Ch. 127,
IRS, Par. 58.22.

L. L. ENGLISH AND WALTER HARTSTIRN*

the following pages, this method of treating trees will
be designated as injection.

There was no foliar injury to the trees at dosages
of 0.5 and 1 ml per inch of tree dbh. At a dosage of
2 ml there was slight injury to the foliage, and at
dosages of 4 and 8 ml there was severe damage, re-
sulting in complete defoliation.

TESTS WITH BARK BEETLES
ON NURSERY TREES

Early May is believed to be the proper time for
treating Americanelm trees with a systemic insecticide
to prevent the first brood of elm bark beetles from
infecting the trees with Dutch elmdisease. In 1959, the

Fig. 4. — Cylindrical sleeve cage for confining insects
on branch of a honey locust tree.

eS SS

first year of our experiments with SD-3562, the chemical
was not available to us until after June 15.

On July 6, 1959, following the tests for phytotoxicity,
three lots of American elm trees in a nursery, each
lot consisting of three trees 3 to 4 inches dbh, were
treated by injection with technical SD-3562 at dosage
rates of 0.25, 0.5, and 1 ml per inch of tree dbh, fig. 3.
To serve as controls, three other trees were similarly
treated, except that distilled water was substituted for
SD-3562.

On July 20, three additional trees were treated
at a dosage rate of 2 ml technical SD-3562 per inch of
tree dbh. As in the previous test, three trees were
used as controls.

An ample supply of bark beetles was obtained
throughout the period of the tests from infested wood
confined in drums fitted with emergence cages. Only
freshly emerged and active beetles were used.

Cylindrical cages were used to confine the beetles
on selected branches of the elm trees. Each cage,
constructed of 40-mesh copper wire screening, was
about 6 inches in diameter and 18 inches long, with
two 15-inch-long muslin sleevés firmly attached to the
ends of the copper wire cylinder, fig. 4. A cage was
slipped over the end of a branch which had 25 to 30
undamaged crotches and was tied in place with twine

around one of the sleeves. About 25 beetles were
counted into a pint carton and transferred promptly to
the copper wire cylinder through the open muslin sleeve,
which was then tied securely.

Cages were placed on trees at intervals of 2, 4, 8,
and 16 days after the trees had received treatment; the
purpose of this procedure was to determine the effective
period of the chemical. Each cage, with beetles in it,
was left on a branch for 7 days; the branch was then
clipped and brought to the laboratory, where the number
of beetle penetrations in the crotches was recorded.
(A feeding scar, caused by a beetle eating into the
xylem, was recorded as a penetration by a beetle.)

There was little, if any, reduction in beetle
penetrations on trees treated at dosage rates of 0.25,
0.5, and 1 ml per inch of tree dbh, but there was a
definite reduction in the number of penetrations at a
dosage rate of 2 ml per inch, table 1. Norris (1959:60)
reported the prevention of feeding niches longer than
2 mm on trees treated by injection with 20 grams of
technical SD-3562 per tree (2 inches dbh); the period
of protection lasted for about 21 days after treatment.
Later, Norris (1960:1035) reported a significant re-
duction in feeding niches with a dosage of 18 grams of
the chemical per 3-inch tree. This second dosage,
which approximates 5.0 ml per inch of tree dbh, is the

Table 1. — Average number of penetrations per beetle in crotches of small elm branches on which bark beetles were
confined in cages. The cages, with approximately 25 beetles each, were placed on the branches 2, 4, 8, and 16 days
after four lots of three trees each had been treated in July, 1959, with SD-3562 (30-50 per cent alpha isomer) by injection
at various dosage rates and left for 7 days; two lots of trees were treated by injection with distilled water only.

Penetrations Per Beetle Caged on Branch

Dosage Rate,

on Indicated Day After Tree Treatment

MI Per Inch

of Tree DBH 2nd 4th 8th 16th
0.0 0.25 0.27 0.64 0.55
0.25 0.38 0.53 0.41 0.79
0.5 0.26 0.22 0.46 0.78
1.0 0.30 0.23 0.35 0.45
0.0 0.55 0.82 PI5 1.29
2.0 0.41 0.25 0.53 0.44

Table 2. — The survival time (number of days) of bark beetles placed in jars with twigs from elm trees 2, 4, 8, 16,
and 32 days after treatment of trees in July, 1959. Four lots of twigs were from 12 trees treated by injection with SD-3562
(30-50 per cent alpha isomer) at various ‘dosage rates. Two lots of twigs were from 6 trees treated by injection with

distilled water only.

Dosage Rate,
Ml Per Inch

Survival Time (Days) of Beetles Exposed to Elm Twigs
on Indicated Day After Tree Treatment

of Tree DBH 2nd 4th 8th 16th 32nd 2-32°
0.0 5 7 6 7 9 6.8
0.25 4 6 4 2 9 5.0
0.5 z) 3 3 2 4 2.8
1.0 3 7 3 4 2 3.8
0.0 7 7/ 3 9 6.5
2.0 2 2B 2 6 3.0

*Average survival time for beetles placed in jars with twigs 2, 4, 8, 16, and 32 days after trees had been treated.

dosage necessary to protect elms from infection with
Dutch elm disease for the 30 days necessary in Wiscon-
sin, Norris concluded.

We originally planned to place a series of cages
on the trees 32 days after treatment, but by that time
the crotches in the twigs were so badly damaged by
the natural infestation of bark beetles that this pro-
cedure proved impractical. However, enough undamaged
crotches were found 32 days after treatment to run tests
with beetles in jars containing twigs from the treated
trees, table 2. These tests showed that the life span
of bark beetles placed in jars with twigs from trees
treated with 0.5, 1, and 2 ml of technical SD-3562 per
inch of tree dbh was about half the normal life span,
table 2. Apparently, some of the beetles were killed
when exposed to twigs from trees given dosages lower
than those required to materially reduce the number of
penetrations, while others survived long enough, even
on branches from trees given the 2 ml dosage, to
produce penetrations in the crotches of twigs.

TESTS WITH SD-3562 INJECTED INTO ELMS
FOR CONTROL OF DUTCH ELM DISEASE

The preliminary tests with SD-3562 as a systemic
insecticide produced several interesting findings.
After injection into American elm trees, SD-3562 was
translocated throughout the trees and was toxic to
bark beetles feeding in the crotches of twigs, where
infection with the Dutch elm disease fungus, Cerato-
cystis ulmi (Buisman) C. Moreau, takes place. The
chemical was toxic to the bark beetles for about a
month after the trees had been treated at dosages of
0.5 ml per inch of tree dbh. At a dosage of 2 ml per
inch of tree dbh, the number of penetrations to the
xylem of the twigs was definitely reduced. This
dosage, however, caused slight injury to the foliage
of elms. There seemed to be little margin between the
dosage level required to reduce the number of beetle
penetrations and the dosage causing injury to elm
trees.

An important question to answer was whether
SD-3562 at nonphytotoxic dosages could provide suf-
ficient protection from the bark beetle to control Dutch
elm disease. Only comprehensive field experiments
could answer this question.

Experiment on Elms at Sinnissippi Forest. — A
field experiment to test the effectiveness of SD-3562
for reducing the incidence of Dutch elm disease was
started in 1960 at Sinnissippi Forest, near the village
of Oregon. The test area contained 162 American elm
trees that ranged in size from 1.5 to 12.3 inches dbh.
On May 13, just after the buds had broken dormancy,
half of the trees (81) were treated by injection with
SD-3562. Half were left as controls. (No holes were
bored and no distilled water was injected into the
trees set aside as controls.) The treated and untreated
trees were chosen at random throughout the block. Un-
diluted technical SD-3562 (30-50 percent alpha isomer)

Table 3. — Number of elm trees at Sinnissippi Forest
showing each of several degrees of chemical damage follow-
ing treatment of 81 trees with SD-3562 on May 13, 1960
(30-50 per cent alpha isomer), and on May 1, 1961 (75 per
cent alpha isomer). SD-3562 was used at the rate of 2 ml
per inch of trunk dbh in 1960 and 1.5 ml in 1961.

Number of Trees

Damage* 1960 1961
ne 6 Se ee ee eee a ee
None 3 31
Slight 35 12
Moderate 24 18
Severe 17 17
Complete (tree killed) 2 l

eT —

*Slight, some cupping of leaves but no dead areas; moderate,
cupping of leaves over the greater portion of the tree, accompanied
by some marginal leaf burn; severe, cupping and burning of leaves
extensive, between the veins as well as marginal, in some cases
one or more branches killed.

was injected into four holes, three-eighths inch in
diameter, in each test tree at the rate of 2 ml per inch
of tree dbh.

On May 1,1961, the same trees were again treated,
this time with the improved technical SD-3562 (75 per
cent alpha isomer) at the rate of 1.5 ml per inch of tree
dbh; the holes drilled were five-sixteenths inch in
diameter. This dosage of the improved chemical was
presumed to have more insecticidal activity than 2 ml
of the older product. At seasonal intervals after being
treated, the trees were examined for disease symptoms
and signs of chemical injury.

The observations on phytotoxicity for both years
are summarized in table 3. None of the untreated trees
showed any signs of injury. Two trees treated with
the chemical died in 1960 and one in 1961. Seventeen
showed severe injury in each year. Although only 3
trees were free of injury in 1960, 31 were without in-
jury in 1961. The significance of these figures is a
matter of conjecture at this stage of the experiment.

There was no evidence of Dutch elm disease in
the entire block of trees in 1960. In 1961, however,
eight of the untreated trees and one of the treated trees
died of the disease, as verified by laboratory tests.
The 1961 losses from Dutch elm disease amounted to
1.2 per cent of the treated trees and 9.9 per cent of the
control trees. The difference between these per-
centages is encouraging, but its significance can be
determined only by continuing the experiment for
several years.

Experiment on Elms in Cook County. — In 1961, a
block of 500 American elm trees ranging in size from
1.0 to 7.4 inches dbh was made available in the Forest
Preserve District of Cook County for tests with the
improved technical SD-3562 product. Three lots of
100 trees each, randomized throughout the entire block,
were treated with the chemical at dosages of 1, 1%,
and 2 ml per inch of tree dbh, respectively. Treatment

Table 4. — Number of trees in the Forest Preserve District of Cook County showing each of several degrees of
chemical damage following treatment of 400 trees with improved SD-3562, each lot of 100 trees at a dosage of 1, 1.5, 2,
or 1+1 ml per inch of trunk dbh, May, 1961. Observations were made in June and September of the same year.

Number of Trees Showing Damage at Indicated Dosage

1 Ml 1.5 Ml 2 Ml 1+1Ml
Damage* June Sépt June Sept June Sept. June Sept.
None 115 | 37 5 28 5 23 1 i be
Slight 16 30 7 30 3 26 7 32
Moderate 23 @) 16 11 15 12 13 13
Severe 44 11 61 11 62 10 68 15
Complete (tree killed) 6 13 11 20 15 29 ll 25

*Damage classifications the same as under table 3.

was by the injection method on May 5, when the buds
of the trees were swollen. A fourth randomized lot
was treated with a split dosage--1 ml per inch of tree
dbh on May 5 followed in 2 weeks with 1 ml per inch.
A fifth randomized lot of 100 trees was left untreated
as a control.

No Dutch elm disease was evident in either the
treated or control lots in 1961. However, considerable
chemical injury was noted in the treated trees. A
summary of the observations, table 4, shows that there
was injury at all dosage levels. By mid-September
the trees killed ranged from 13 per 100 at a dosage of
1 ml to 29 per 100 at a dosage of 2 ml per inch of tree
dbh. The observations indicate the ability of many
trees to overcome the toxicity of the chemical when
the damage is slight or even severe. Trees of 3 inches
dbh or smaller appeared to be more easily killed by
the chemical than larger trees. The larger trees re-
covered more readily fromnonfatal injury than the small
ones. Chemical injury in the Forest Preserve District
of Cook County was much more severe than at Sinnis-
sippi Forest or in the Wisconsin areas included in
some tests by Norris (1960:1035), who reported only
0 to 5 per cent injury following a dosage, applied in
May, of 6 grams per 3-inch tree (equivalent to 5 ml per
3-inch tree or 1 2/3 ml per inch of tree dbh).

TESTS AGAINST OTHER PESTS WITH SD-3562
APPLIED TO TREES BY SEVERAL METHODS

Sixteen honey locust trees were divided into four
groups of four trees each, the groups were designated
A, B, C, and D, and the trees were designated as in
table 5. One tree in each group was set aside as a
control. On June 14, 1961, three trees in each group
were treated with improved technical SD-3562 at dos-
ages of 1, 2, or 3 ml per inch of trunk dbh by one of
the four methods described below; methods A, B, C,

and D were usedon groups A, B, C, and D, respectively.

A. The chemical was injected into four holes,
each five-sixteenths inch in diameter, drilled in the
trunk of a tree, fig. 3. The holes were then plugged
with dowels.

B. The chemical was applied with a syringe to
the surface of the bark entirely around the trunk about

3 feet above the groundand allowed to rundown, fig. 1.
This method of application was similar to methods
employed by Jeppson et al. (1952:669).

C. The chemical was applied to the bark as in
method B. It was then loosely covered with thin plastic
to reduce weathering.

D. The chemical was applied as in method B to
bark that had been striated with a razor blade at
intervals of about one-fourth inch to a depth of one-
eighth inch.

Some yellowing and dropping of leaflets was noted
on trees treated with dosages of 2 and 3 ml by method
A and with a dosage of 3 ml by method D. The damage
was not severe. No damage was noted in 1961 on trees
treated by methods B or C.

Bagworm on Honey Locust. — In the second week
after treatments by methods A, B, C, and D described
above, about 25 larvae of the bagworm, Thyridopteryx
ephemeraeformis (Haworth), were confined in sleeve
cages, fig. 4, one cage on each of the four trees that
had previously been treated with a dosage of 3 ml of
SD-3562, and one cage on the control tree in group A,
table 5. Extent of the kill showed that the chemical
had been translocated to the foliage in all but one of
the trees in sufficient quantity to be highly toxic to
the bagworms.

Each week, from the third week through the ninth
week after application of the chemical, a cage with
about 25 bagworm larvae was placed over a branch of
each of the 16 trees. After a period of 1 week, each
caged branch was clipped from the tree, and branch
and cage were taken to the laboratory for examination.
A new group of bagworms was caged on another branch
of each tree for the following week.

The chemical applied by each of the four methods
of treatment and at each of the three dosages was
highly toxic to the bagworms, table 5. The most con-
sistent and persistent effect was obtained by method A,
that is, with the chemical injected into holes in the
trees. Here, with one exception, a complete kill of
bagworms was obtained at each of the three dosages
through the ninth week after treatment. Method D, with
the chemical placed on striated bark, gave the next
best results. This method gave high, although not
always complete, kills through the ninth week. When

>

Table 5. — Per cent of caged bagworms found dead in each of several weeks on each of 16 honey locust trees.
Twelve trees were treated with improved SD-3562 on June 14, 1961. Each lot of caged bagworms was left on a tree for
7 days. The methods of application are indicated by letters in the tree numbers and are discussed in the text.

Per Cent of Bagworms Dead

Dosage Rate, in Indicated Week After Tree Treatment

Tree MI Per Inch a
No. of Tree DBH 2nd 3rd 4th Sth 6th 7th 8th 9th
A-l 0 40.7 16.0 8.0 0.0 28.1 14.3 30.0 21.9
A-2 1 HAG 100.0 100.0 100.0 100.0 100.0 100.0 100.0
A-3 2 ete 100.0 100.0 100.0 91.6 100.0 100.0 100.0
A-4 3 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0
B-l 0 21.0 15.4 sie! Leia, 211 39.3 37.8
B-2 1 100.0 96.0 100.0 87.8 100.0 100.0 72.4
B-3 2 100.0 100.0 97.0 100.0 91.4 90.0 84.0
B-4 3 30.4 100.0 100.0 100.0 100.0 97.0 7.4 93.8
C-l 0 15.0 9.1 0.0 16.7 222 3.6 42.4
C-2 1 100.0 100.0 70.3 90.6 81.2 96.9 73.4
C-3 2 Ais 100.0 89.0 64.5 93.0 90.2 94.7 7.8
C-4 3 91.8 100.0 100.0 100.0 100.0 100.0 97.0 89.2
D-1 0 0.0 8.0 6.2 P2247) 25.0 73.5 62.1
D-2 1 100.0 100.0 100.0 100.0 100.0 97.1 7.0
D-3 2 aries 100.0 100.0 100.0 100.0 nd 90.9 87.0
D-4 3 100.0 100.0 100.0 100.0 100.0 100.0 94.1 100.0
Approximate length
of bagworms, inches 1/4 1/2 3/8-1/2 1/2 1/2-3/4 3/4 3/4-1 acca
*No record.
Table 6. — Per cent of mimosa webworms found dead in cages on each of 16 honey locust trees at various times.

On 12 of these trees, improved SD-3562 had been applied on June 14, 1961 (same trees as in table 5). Each lot of caged
mimosa webworms was left on a tree for 7 days during the sixth and tenth weeks after treatment and for 14 days during
the eleventh and twelfth weeks and the thirteenth and fourteenth weeks. The methods of application are indicated by
letters in the tree numbers and are discussed in the text.

Per Cent of Webworms Dead

Dosage Rate, in Indicated Week or Weeks After Tree Treatment

Tree MI Per Inch
No. of Tree DBH 6th 10th 11th-12th 13th-14th
A-1 0 0 0 1.8 0
A-2 1 100.0 66.6 100.0 100.0
A-3 2 100.0 29.4 100.0 100.0
A-4 3 100.0 100.0 100.0 100.0
B-l 0 0 ae 0 3.3
B-2 l 100.0 100.0 100.0 100.0
B-3 2 100.0 100.0 100.0 100.0
B-4 3 100.0 100.0 100.0 100.0
C-l 0 0 0 0 )
C-2 i 100.0 100.0 100.0 100.0
C3 2 100.0 ae 88.8 100.0
C-4 3 100.0 66.6 100.0 100.0
7s Bw
D-1 0 0 0 3.3 gos
D-2 l 100.0 0 100.0 F 3 &
D-3 2 100.0 hy 100.0 Acs
D-4 3 . 100.0 50.0? Bau
O62

*Observations incomplete.

“N

the chemical was placed on the bark of a tree (method
B), high kills were maintained through the eighth week.
The bark application covered with plastic (method C)
was no more effective than the uncovered application
(method B), table 5.

Bagworms introduced into the cages in any week
after the first were larger than those used the previous
week. Exposing the bagworms to the chemical for more
than 1 week probably would have resulted in higher
kills than those shown in the table.

Mimosa Webworm on Honey Locust. — At irregular
intervals after application of SD-3562 to honey locust
trees in groups A, B, C, and D, table 6, nests con-
taining larvae of the mimosa webworm, Homadaula
albizziae Clarke, were confined in cages on the trees.
In the first two tests, in the sixth and tenth weeks
after the trees were treated, each caged branch was
clipped from the tree at the end of 7 days, and branch
and bag were taken to the laboratory for examination.
Although the number of larvae recovered in cages on
treated trees was low (small dead larvae are very
difficult to find in leaf debris), the results showed
rather conclusively that SD-3562 applied by each of
the four methods was highly effective during the sixth
week after treatment, table 6. A drop in kill during the
tenth week was noted on some of the trees; subse-
quently the cages were left on the trees for 2-week
periods. The longer exposure resulted in complete
kills of larvae on most trees through the period of the
experiment, table 6. On trees treated by method B,
bark application, complete kills were recorded for all
periods of observation.

Mite on Honey Locust. — On August 4, 8 weeks
after the application of SD-3562 to honey locust trees
in the experiment for control of bagworms, table 5,
honey locust leaves infested with the honey locust
mite, Eotetranychus multidigituli (Ewing), were taped
to leaves on the trees in group A. Counts made 2
weeks later indicated a complete kill of mites on all
the treated trees in this group.

Fall Webworm and Walnut Caterpillar on Honey
Locust. — Larvae of the fall webworm, Hyphantria
cunea (Drury), and the walnut caterpillar, Datana inte-
gerrima Grote & Robinson, were caged on honey locust
trees in group A during the tenth week after the appli-
cation of SD-3562. The chemical was highly effective
against the larvae of the fall webworm. Results of the
test involving the walnut caterpillar were inconclusive.

ADDITIONAL TESTS FOR CONTROL
OF MIMOSA WEBWORM

SD-3562 was applied on July 25, 1961, to the
uninjured bark of a honey locust tree, 30 feet tall and
6 inches dbh, at the rate of 2 ml per inch of trunk dbh,
fig. 1. After treatment, the treated area was covered
with a hardware cloth cylinder and heavy kraft paper
as a safety measure and to reduce weathering, figs. 5
and 6. The application of SD-3562 was effective

within a week after treatment and provided excellent
protection for about 5 weeks. The tree was treated
again on September 6, when some of its new growth
was found to be infested. This tree was virtually free
of any sign of webworm damage at the end of the
growing season.

Fig. 5 (left). — Hardware cloth around the trunk of @
honey locust tree treated with SD-3562. This is a safety
measure used on trees in residential areas to keep human
beings and pets from coming in contact with the chemical.
The hardware cloth was removed 2 weeks after the tree had
been treated.

Fig. 6 (right). — The tree shown in fig. 5. Paper cover-
ing has been added over the hardware cloth to give further
protection to human beings and pets and to reduce weather-
ing of the chemical. The paper was removed 1 week after
the tree had been treated.

Webworm infestations on three other honey locust
trees were quickly brought under control with appli-
cations of technical SD-3562 to uninjured bark at the
rate of 3 ml per inch of trunk dbh.

Results of the tests with these four trees were
evaluated at weekly intervals by examining the larvae
in nests clipped from the treated trees and from near-
by untreated trees. No sign of phytotoxicity was
observed during 1961 in any of the treated trees.

TESTS WITH FALL WEBWORM ON OAKS

Five small oak trees, red, pin, and bur, 1 to 2%
inches dbh, were treated on July 31, 1961, with im-
proved technical SD-3562 injected into the soil, fig. 2,
at dosages ranging from 5 to 40 ml per inch of trunk
dbh. Each dosage was diluted with 8 gallons of water.
One tree was left untreated as a control. At weekly
intervals, beginning 2 weeks after treatment and ending

with the fifth week, larvae of the fall webworm were
confined in cages, one cage on a limb of each of the

Fig. 7. — Trunk of a pin oak tree 17 days after the bark
; had been stippled with an ice pick and SD-3562 had been
applied to the surface. Circular areas are depressed as a
| result of tissue damage caused by the chemical.

|
|
|

six trees. Larvae were exposed for 1 week. The results
were inconclusive.

Applications of technical SD-3562 to the unin-
jured bark of red oak trees, 1% to 3 inches dbh, at
dosages of 1 to 4 ml per inch of trunk dbh also gave
inconclusive results.

In a series of tests on pin oaks, 2 to 3 inches
dbh, a dosage of 3 ml per inch of trunk dbh was applied
on August 29 by three methods: on uninjured bark, on
bark stippled with an ice pick, and into holes drilled
in the trunk, one tree for each method and one as a
control. One lot of fall webworms was caged on each
tree 2 weeks after treatment and another 3 weeks after
treatment. Application of SD-3562 to uninjured bark
was not appreciably effective against the fall webworm
larvae. The chemical apparently did not penetrate
uninjured oak bark as readily as uninjured honey locust
bark. However, applications of the chemical by the two
other methods were highly effective against the larvae.
SD-3562 when applied to stippled bark appeared to
be taken up by the tree as quickly as when applied in
drilled holes. Chemical injury to bark but not to foliage
was observed on the treated oak that had been stippled
with an ice pick, fig. 7, as well as on the tree drilled
with holes. No chemical injury to either bark or foliage
was seen in 1961 or 1962 on the tree treated on un-
injured bark.

TESTS WITH SD-3562 INJECTED INTO SOIL

In 1961, diluted SD-3562 injected into soil was
tested against certain pests of arborvitae, Canaert
red cedar or juniper, and honey locust.

Bagworm on Arborvitae. — Six arborvitae plants
about 4 feet high were treated July 11, 1961, with im-
proved technical SD-3562 at dosages of 0, 5, 10,20,
40, and 80 ml per plant, respectively. Each dosage,
diluted with water to make 1 gallon, was injected with
a pump and wand, fig. 2, into the soil in eight places
around the plant and at a distance of about 10 inches
from the stem. The wand was slanted under the plant
at an angle of about 45 degrees; the holes made were
6 to 10 inches deep. At the time of treatment, the soil
was wet. At about weekly intervals, 30 to 50 bagworms
were placed on each plant by hand and left there for
7 or 8 days before being removed and examined.

Effectiveness of the chemical was evident within
7 days after treatment at all dosage levels; within this
period, complete kills were obtained at dosages of 40
and 80 ml per plant, table 7. Complete kills were ob-
tained 15 days after treatment with dosages of 10, 20,
40, and 80 ml; the kill was only partial with the 5-ml
dosage. Forty-three days after treatment, the 80-ml
dosage gave a 100 per cent kill of bagworms with bags
up to 1 inch long. The treatments resulted in no ap-
parent phytotoxic injury to arborvitae.

Midge on Canaert Red Cedar. — Canaert red cedar
plants in a local nursery provided an opportunity for
tests against a midge, Oligotrophus sp., whose larvae

damage the tips of the plants. The red cedars, about
3¥, feet high, were heavily infested with the pest. One
plant was used for each of the following dosages of
improved technical SD-3562: 2%, 5, 10, and 20 ml,
each diluted with water to make 1 gallon. On July 11,
1961, the diluted chemical was injected into the soil
in the same manner as in the experiment described for
control of bagworm on arborvitae. One untreated plant
was used as a control.

Within 15 days after treatment, very substantial
kills of larvae and pupae were obtained, even at the
lowest dosage of 24% ml per plant. Twenty-two days
after treatment, the kill was 100 per cent at dosages
of 5, 10, and 20 ml per plant. All dosages provided
practical control for the season, table 8. The chemical
produced no apparent injury to the red cedars.

Mimosa Webworm on Honey Locust. — On July 24,
1961, a honey locust tree with a trunk 4 inches dbh
was treated with 80 ml of technical SD-3562 in 8
gallons of water. One quart of the dilute chemical was
injected into the soil in each of 32 places in a regular
pattern around the tree beginning 1 foot from the trunk
and extending approximately to the periphery of the
branch spread. This treatment failed to control the
larvae of the mimosa webworm.

Three additional trees ranging in size from 34 to
4Y, inches dbh were treated on July 26, at rates of 5,
10, and 20 ml per inch with technical SD-3562 in the

same manner as above. When control of the mimosa
webworm was not evident within 3 weeks, the treatment
was repeated, but with each dosage in 4 gallons of
water injected into eight places in the soil 1 foot from
the trunk of the tree. These two soil treatments on
each of the three trees failed to control larvae of the
mimosa webworm.

DAMAGE TO BARK AND TISSUE

The application of technical SD-3562 to small
honey locust trees by injection killed a considerable
area of the bark and tissue around each injection hole,
fig. 8. Serious injury was caused when the chemical
was applied over striated bark, fig. 9. The bark of a
pin oak stippled with an ice pick before being treated
with SD-3562 was noticeably injured within 17 days
after treatment, and by May, 1962, the injured areas
had greatly enlarged.

On honey locust trees, the uninjured trunk areas
treated with SD-3562 in 1961 became delineated with
a slightly darker color of the bark, but no evidence of
actual bark injury was observed until the following
spring. When examined in May, 1962, some trees
showed no signs of bark injury. Others showed various
degrees of injury in the form of cracks or checks in
in the bark, fig. 10. Injury appeared to be confined to
the outer phloem (bark). Additional research will be

Table 7. — Per cent of bagworms found dead on each of several days on each of six arborvitae shrubs, about 4 feet
high, five of which had been given soil treatments with improved SD-3562, July 11, 1961. Each lot of bagworms was
placed on a shrub, left there for 7 or 8 days, and removed, examined, and counted on the day indicated.

Dosage Rate,

Per Cent of Bagworms Dead

on Indicated Day After Plant Treatment

Ml Per Plant 7th 15th 22nd 29th 36th 43rd

0 8.8 0 NO) 22 Sy 24.1 8.7

5 41.0 47.6 59.4 20.0 22.2 15.0

10 87.0 100.0 100.0 96.5 91.5 50.0

20 915 100.0 100.0 100.0 92.9 77.7

40 100.0 100.0 100.0 100.0 91.3 95.1

80 100.0 100.0 100.0 100.0 100.0 100.0
Approximate length

of bagworms,
inches 3/8 1/2 1/2-3/4 5/8-3/4 3/4 3/4-1
Table 8. — Per cent of midge population (Oligotrophus sp.) found dead on each of several days on each of five

Canaert red cedar plants, four of which had been given soil treatments with improved SD-3562, July 11, 1961. The per
cent of the midge population dead was determined by counts made on 100 red cedar buds each day indicated.

Per Cent of Midge Population Dead
on Indicated Day After Plant Treatment

Dosage Rate,

MI Per Plant 7th 15th 22nd 27th 36th 40th 54th 70th
0 20.8 8.1 23.) 0 Ee) 4.0 0 0
2% 18.3 80.0 82.7 91.5 100.0
5 23.1 95.6 100.0 100.0
10 20.7 100.0 100.0 100.0
20 2G 96.3 100.0 100.0

10

Fig. 8.—Scar in the trunk of a honey locust tree 3
months after treatment with SD-3562. A hole had been drilled,
SD-3562 injected, and the hole plugged with a dowel.

|
|
|

Fig. 10. — Bark of honey locust trees in May, 1962,
japproximately a year after being treated with technical
\SD-3562. A. Small tree in nursery: bark in upper part of
‘picture was not treated; bark in lower part shows chemical
jinjury. B. Tree of medium size along street: treated bark
jin lower part of picture shows injury; untreated bark above
\does not.

-~-—---—--

a

eS ee

i
}

Fig. 9. — Trunk of a honey locust tree 3 months after
the bark had been striated with a razor blade and SD-3562
had been applied to the wounded surface.

required to establish the significance of this injury
and to develop methods for avoiding it.

When observed in May, 1962, none of the honey
locust or oak trees treated with SD-3562 in 1961 showed
foliar damage.

DISCUSSION

Systemic insecticides, such as SD-3562, open up
interesting possibilities for the control of tree and
shrub pests for which there is now no practical control.
In addition, they offer possibilities for the develop-
ment of improved and more effective means of con-
trolling pests for which controls are now known.

SD-3562 is toxic to the smaller European elm bark
beetle, a vector of Dutch elm disease, and may have
possibilities for reducing the incidence of this disease.
It is effective against the mimosa webworm on honey
locust trees when a small quantity of the chemical is

11

applied to the uninjured bark of the tree at the proper
time. It shows possibilities for providing a control
measure for the midge Oligotrophus sp., a troublesome
pest of ornamental junipers or red cedars, for which
there has been no satisfactory control. Experiments
indicate that SD-3562 is toxic to the bagworm and
mimosa webworm at lower dosages and over a much
longer period of time than it is to the European elm
bark beetle.

One of the problems in the use of a systemic
insecticide is the selection of the proper method of
application. There are three general methods: the
chemical can be sprayed on the leaves of the plant,
it can be placed in the soil, or it can be placed in or
on the trunk of the plant. The first method, foliar
spraying, seems to offer the least advantage over
methods that use nonsystemic insecticides. Soil appli-
cations offer practical possibilities but, with such
variables as soil type and moisture, effective dosage
levels are difficult to establish. Then, too, a great
deal of the chemical is wasted in soil applications.
At this time, the introduction of the chemical through
the trunk into the sap stream of a tree commands a
great deal of interest because of the possibility of
obtaining quick, positive results with a small quantity
of chemical.

Methods of treating trees with SD-3562 by means
of holes drilled into the trunk, or by other means that
make wounds in the trees, appear to be fundamentally
unsound. Small, thin-barked trees, such as honey
locust, react rather violently to wounds, especially
when the wounds are laved with the chemical, figs. 8
and 9. Accidental wounds or wounds made in the bark
by insects may be the foci of chemical injury. Such
injury is unacceptable if yearly treatments are neces-
sary, as, no doubt, they would be for control of most
tree pests.

Although the method involving chemical appli-
cation to uninjured bark may not be effective on all
kinds of trees, such applications seem to be on a
sounder footing than methods requiring damage to the
bark.

LITERATURE CITED

Jeppson, L. R., M. J. Jesser, and J. O. Complin

1952. Tree trunk application as a possible method of using systemic insecticides on citrus. Jour. Econ. Ent,

45(4):669-71.
Norris, Dale M., Jr.

1959. Potentialities for systemic control of the insect vectors of Dutch elm disease. N. Cent. Branch Ent. Soc.

Am. Proc. 14:59-60.
Norris, Dale M., Jr.

1960. Systemic insecticidal action in the cortical tissues of elm twigs. Jour. Econ. Ent. 53(6):1034-6.

12

Coupled with its advantages, SD-3562 has some
drawbacks. Since the chemical is very poisonous and
since it is phytotoxic at some dosage levels, details
of handling, usage, and application, as well as dosage
levels for both pests and plants, must be worked out.
On the basis of our work, it appears that further re-
search is needed before we can recommend SD-3562
for use by the public.

ABSTRACT

Tests with technical grade SD-3562 injected into
elm trees in a nursery showed that this systemic
chemical, although effective at some dosages against
the smaller European elm bark beetle, the principal
vector of Dutch elm disease, presented the problem of
little margin between effective dosage to control
beetle penetrations and chemical injury to the trees.

Field tests with SD-3562 injected into elms to
control Dutch elm disease, although encouraging, were
inconclusive and should be continued. Small elm trees
seemed more vulnerable to injury by the chemical than
large ones.

Experiments with honey locust trees showed that,
after application of the chemical to the uninjured bark,
the trees were toxic to the bagworm, the mimosa web-
worm, the honey locust mite, and the fall webworm.

SD-3562 was effective against the fall webworm
on oaks only when applied to injured bark or through
holes in the trunk; injury to the bark resulted. The
chemical apparently did not penetrate uninjured cak
bark as readily as uninjured honey locust bark.

Diluted SD-3562 injected into soil around arborvitae
and Canaert red cedars provided excellent control of
bagworms and midges, respectively. Injected into the
soil around honey locusts, it failed to control mimosa
webworms on the trees. j

The basic problems in using a systemic insecti-
cide were found to be (a) development of methods
application and dosages that will not injure plants but
will provide control of pests and (b) development of
safe methods for handling a highly poisonous chemical.

vere ers :
etenee en

Sirsa

Sh

SRO a
Reet bet

ue
u

+

OVA e TS