The mango weevil : (Cryptorhynchus magniferae Fabr.)

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Hawaii Agricultural Experiment Station,

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TGs SMITE, SPECIAL; AGENT IN .CHARGE.

PRESS BULLETIN NO. 17.

THE MANGO WEEVIL.
(Cryptorhynchus mangiferae Fabr.)

By De i VAN DINE,

Entomologist, Hawaii Experiment Station, United States De-
partment of Agriculture.

The destructive work of the mango weevil in the seeds of
mangoes was noted in Hawaii for the first time last year. The
nature of the insect and its injury point it out to all persons
- interested in the culture of the mango as a serious pest. In
the family Curculionidae, to which this beetle belongs, occur
numerous species of the most injurious character. The cotton
boll-weevil has destroyed over $50,000,000 worth of cotton in
the Southern United States since its appearance in Texas in 1892.
The curculios of the apple, plum, quince and strawberry do enor-
mous damage to these and related fruits. The chestnut weevil
and the acorn weevil, extending their injury to other nuts, have
added greatly to the evil reputation of this family of beetles.
Looking in the future to the Mainland as a market, it is readily
seen that to prevent an embargo on mangoes, this enemy must be

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controlled and its widespread distribution throughout the islands
of the group prevented. The present limited knowledge of the
mango weevil is herewith presented to aid those interested in
the problem in formulating an outline of warfare.

LOS STORY

Mir AL Schwarz, of the United States Bureanvor yee
mology, to whom the writer is indebted for the determination
of the mango weevil, says in a letter, under date of July 26, 1905:

The weevil is Cryptorhynchus mangiferae, originally described by
Fabricius (Systema Entomol., p. 139, 1774) without locality. Since that
time it has often been described and figured. I think that, after all,
the best description is that by Boheman in Schoenherr’s Gen. et. Spec.
Curc, vol. IV, pt. 1, p. or. Its origmal home is uncertain, tome simes
many years it has spread (no doubt through the agency of man) through-
ut the “Oriental Region” from Madagascar through India, Ceylon, etc.,
to Java and other Malayan Islands. It probably occurs now also in
‘many of the islands of the Pacific Ocean, although I fail to find any
records. The species is not enumerated by Sharp from the Hawaiian
Islands and is no doubt a recent introduction there.

The weevil appears to be extremely injurious to mangoes, and ac-
‘counts of its ravages are numerous. The literature is, however, nct
easily «ccessible, the most available reports being in the “Indian Museum
Notes” (at several places). A paper on the mango weevil by Mr. Sim-
‘mons, read before the Calcutta Microscopical Society is referred to in
Nature, Vol. 37, 1888, March 22, p. 492, and there seems to be a full ac-
count in a work (which I have not seen) entitled “Les insectes nuisibles
au Manguier a l’ele Maurice” par D. L’Emmery de Charnoy, Paris, 1808.
The oldest economic and illustrated account appears to be by Hubner in
ithe ‘‘Naturforscher,’’ vol. XXIV, 1789, a publication quite unknown to
me. Larva and pupa are tolerably well figured in the “Indian Museum
Notes.”

The following is taken from an article by Mr. E. C. Cotes in
ithe “Indian Museum Notes”: 1

*E. C. Cotes, Further Notes on Insect Pests, Indian Museum Notes,
“Calcutta, vol. I, 1889-1891, No. 11, The Mango Weevil (Cryptorhynchus
mangiferae), pp. 45-46. Plate. (Taken from a paper by W. J. Simmons
in the Journal of the Agricultural and Horticultural Society of India,
‘Volume VIII, Part II, new series.)

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The geographical range of the pest under consideration is extensive.
It 1s found in the Isle of France and in Madagascar, and it would be
interesting to learn something about its ravages, and to ascertain when
it was first observed, how supposed to be introduced, etc.. in the islands
named. It does not yet affect all the mango-producing districts of India,
but its march is progressive. Restricted apparently at one time to Dacca
and the Southeastern districts, Backergunge, Furridpore, etc., I learn it is
working its way westward and northward, and throughout Bengal and
the neighboring districts. An article on the subject will be found at
page 558 of Reis and Rayyet for 1885, in which we are told that this
insect-pest has invaded the Presidency, and that in the season of 1885 it
showed itself in the well kept orchard of Kaly Kissen Tagore. I learn
from a gentleman residing in Ballygunge that every tree in his garden is
infected. Reis and Rayyet also informs us that Slyhet was formerly
practically free from this circulio, two or three mangoes per 1,000 alone
being tainted. During the last few years the pest has gained ground so
rapidly in Sylhet that now not a single tree nor fruit is free.

ITS INTRODUCTION

The mango weevil is not recorded by Dr. R. C. L. Perkins in
that part of Fauna Hawaiiensis, published in 1900, dealing with
the family of beetles to which this species belongs. As the col-
lection of the species therein recorded by Dr. Perkins ceased
some two years previous to the above date, it is almost certain
that the weevil of the mango has been introduced since 1898. It
came from India, or possibly the Philippines, if it occurs in the
latter country, since mangoes have been shipped to Hawai from
both places. The beetle was introduced either during the de-
velopmental period in the seeds or in the hibernated state in the
soil about plants from the infested countries, or possibly even in
packing or crevices of boxes containing plants.

ITS. OCCURRENCE IN HAWAII

The mango weevil is first recorded from the Hawaiian Islands
by the writer in August, 1905.1 The first specimen observed was

*Pacific Commercial Advertiser, Honolulu, August 11, 1905, p. 3, and
The Hawaiian Forester and Agriculturist. Vol. II, No. 8, (August), Hono-
lulu, 1905, pp. 231-233.

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a pupa that Mr. J. E. Higgins discovered July 5, 1905, within
the seed of a mango that he had collected at Mr. Allan Herbert’s
former place at Kalihi, Island of Oahu. Two days later the
writer visited the district of Moanalua, this Island, and there
found larvae, pupae and adults within the seeds of various varie-
ties of mangoes. Mr. Donald MacIntyre, Superintendent of
Moanalua Gardens, had not noticed the presence of the weevil in
the seeds for the reason that for the past two years he had not
removed the husks from the seeds before planting them. For
seven years previously, however, Mr. MacIntyre informed the
writer that he had practiced the removal of all husks before
planting seeds in the nursery and it is reasonable to suppose from
this that the weevil made its advent into the Moanalua Gardens
not earlier than 1903. Inquiry of Mr. David Haughs, Mr. J. E.
Higgins and Mr. G. P. Wilder, all prominently interested in
mango culture, brought out the information that the weevil had
not been observed in Honolulu up to the summer of I905. Mr.
Haughs, in his connection with the Territorial Government Nur-
sery, has planted mango seeds for many years and has practiced
removing the husks from the seeds for horticultural reasons.
The distribution last year, then, so far as is known, was con-
fined to this Island (Oahu) and extended from Kalihi to Moana-
lua.

In July, 1906, Mr. Alexander Craw in a report as Superin-
tendent of Entomology to the Territorial Board of Commission-
ers of Agriculture and Forestry, recorded the mango weevil as
having been found this season from Palama, Honolulu, to Pearl
City

Mr. Otto Swezey informed the writer that he found specimens
of the larvae, pupae and! adults within the seeds of ripe fallen
mangoes on Gulick avenue, Honolulu, on June 12th, 1906, and
Dr. R. C. L. Perkins likewise states that he had found mangoes
infested with the beetle this season at his home in Nuuanu Val-
ley. The beetle is seen to have extended its distribution over a

*Hawaiian Forester and Agriculturist, Vol. III, No. 7, (July), Hono-
lulu, 1906, pp. 198-199.

Press Bul. 17, Hawaii Agr. Expt. Station.

THE MANGO WEEVIL (Cryptorhynchus mangiferae) AND ITS
INJURY.

__ Explanation of Plate: A, Larvae, pupae and adults of the weevil,
slightly reduced. _B, a seed showing exit of adult weevil after completing
development within. C, half a mango with fully developed larva within

newly prepared pupal cell. D, half of mango showing destruction to
seed. (Photographs by the author.)

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5
considerable area during the past year. It is known that man-
goes were shipped to the Island of Maui last year from the in-
fested district (before the presence of the weevil had been dis-
covered), and it is probable that the weevil has been carried to
that island. To date the reported distribution is confined to the
Island of Oahu and extends from Nuuanu Valley, Honolulu, in
the Ewa direction to Pearl City.

THE WEEVIL AND ITS LIFE-CYCLE (See Plate I, A.)

As a beetle, the mango weevil has a thick pair of wing-covers
which, when folded together at rest, give the body the appear-
ance of a shell. The wing-covers are much rounded and ex-
tremely hard. As a weevil, the head is prolonged in front into
a beak or rostrum, bearing the antennae on its sides and the
modified mouth-parts at the extreme end. The mouth-parts are
formed for gnawing. In the mango weevil, the beak is short
and thick and when at rest is turned back beneath the thorax in a
groove terminating between the first pair of legs. The adult
weevil varied from 1/4 of an inch to 5/16 of an inch in length
in the specimens measured. When newly developed, the adult
is a whitish pink in color, but soon changes to a dark brown
with yellowish markings. |

The beetle feigns death on being disturbed and drops to the
ground with the head drawn well under the thorax and the legs
folded beneath the body. Its protective resemblance to coarse
earth and debris is particularly noticeable. Nothing has been
observed in regard to the food habits of the adult.

The eggs of the mango weevil were found on mangoes from
one-half to three-fourths fully grown, situated alongside a slight
incision on the rind. The writer has not observed egg-laying or
carefully noted the habits of the weevil as regards oviposition, but
is inclined to think that the eggs in the instances seen were prob-
ably placed within the incision or cavity and later forced out by
the exudation of juice, an amount of which in a dried condition
enveloped them.

The larvae in appearance are, generally speaking, like the sugar-

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cane borer (the larva of Sphenophorus obscurus), that is, foot-
less, ‘‘fleshy” grubs, light in color, with a dark head. The en-
tire development after hatching from the egg is undergone within
the seed. When fully developed, the larva constructs a pupal
cell, surrounded simply by the excrement, within the tunnel
formed by feeding, and transforms to the pupa. The inactive
pupa is perfectly white in color with the developing head, legs,
wings and body-parts plainly indicated. |

The length of the various stages 1n the life-cycle of the mango
weevil can be given only approximately from this year’s notes.
In the locality under observation, the adults became active about
May 16th. ‘The first newly hatched larvae were to be seen from
May 28th on. Pupae were found on June 27th and adults on
July 3rd. The first adult weevils seen of this year’s brood were
those reported by Mr. Swezey, taken by him June 12th on Gulick
avenue, Honolulu. The mango crop in that locality, however,
was nearly a month earlier than at the place where the above
notes were taken. The life-cycle appears to be approximately
4o days in length and there can be but one brood a year.

ITS HIBERNATION

The various stages of the mango weevil were found last sea-
son all through July, following the discovery of the insect. Not
more than one specimen was found in any one seed. During
August, refuse seeds and the seeds of fallen mangoes contained
some pupae and many adults. As late as September 11th the
seeds beneath trees in the infested district contained adults but
in no great numbers. It appeared that the beetles remained in
the seeds for a time after completing their full development. On
the last date mentioned, September 11th, three living adults were
removed from as many seeds and placed in a tightly corked phial
beneath a plug‘ of cotton. On October 13th all of these speci-
mens were living. The writer was absent from the Territory for
nearly a month, but upon his return, November 15th, one weevil
had died. Another weevil failed to show signs of life on Janu-
ary 3rd. The third specimen lived until February roth. From

Press Bul. !7, Hawaii Agr. Expt. Station. PLaTe ||

Fig. 1—A fence beneath mango trees that contained numbers of
hibernated weevils in cracks, crevices and behind the boards where nailed
to the posts. Hundreds were found in one board that had been previ-
ously riddled by termites. the tunnels of the latter affording an excellent
place of concealment. (Photograph by the author.)

Fig. 2—A stone wall beneath mango trees in which hibernated
weevils where found in large numbers. (Photograph by the author.)

PLACES IN WHICH HIBERNATED WEEVILS ARE FOUND.

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these observations it was evident that the insect could pass a con-
siderable period in an inactive state. The same date the above
experiments were begun, a quantity of seeds from fallen man-
goes from the infested district was placed in a breeding cage.
The idea was to determine the length of time the adults would
continue to appear from within the seeds. After making an
exit through the husks the beetles showed no tendency to remain
within the seeds. Apparently nearly all the weevils had left;
however, on October 4th, four specimens were found on the wire
screen above the seeds. One specimen appeared on October 15th
and on November 16th the seeds were all taken out and ex-
amined and two dead specimens were found out of the seeds on
the floor of the breeding cage, having issued from the seeds be-
tween October 15th and the last date mentioned during the ab-
sence of the writer. No weevils were contained in the remain-
ing seeds.

At this time a visit was made to the infested district and all
traces of the weevil had disappeared. Diligent search failed to
show where they were until January 30th when the writer found
them by the hundreds in the crevices of an old board fence and
stone wall beneath a group of neglected mango trees in a de-
serted kuleana in Moanalua Valley. (See Plate IJ.) The writer
believes that the larger portion of the weevils went into hiber-
nating quarters in similar places during the latter part of August
and the first part of September. The weevils were found in a
state of hibernation in that particular locality up to May 16th.
An active beetle was observed on the foliage of a nearby mango
tree on that date. At this time the fruit crop was about one-
half grown.

tS ENTRANCE TO THE SEED

From May 16th on, hundreds of mangoes were sectioned in
halves to find, if possible, evidences of the larvae within the
seeds. May 28th one newly developed larva was found within
the seed of a nearly full-grown mango. In several instances
thereafter newly hatched larvae were found within the seed and

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a faint, irregular discolored line or track leading from the tiny
burrow within the seeds through the husk and into the flesh, indi-
cated the mode of entrance. It is to be seen from this that the
fruit is infested rather. late in its development. The larva, ap-
parently, on hatching from the egg on the rind or in the flesh,
burrows at once to the seed within the husk and the resulting in-
jury to the tissues of the fruit is so slight that soon all evidences
of the means of entrance become effaced.

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The mango weevil is not known to attack any other fruit. Its
injury to the mango is primarily the destruction of the seed. The
incisions in the rind do, of course, blemish the fruit and offer
places of infection for the germs of decay. In the first lot of
mangoes examined on July 7, 1905, it was estimated that about
60 per cent. were infested, that is, out of 44 seeds examined, 28
contained either the larval, pupal, or adult, weevil. The in-
spection of another lot of seeds six days later resulted as follows,
16 seeds each of the ‘“‘Number 9,” the Chutney and the so-called
“Hawaiian” variety being taken: Of the Number 9, 5 were in-
fested; of the Chutney, 10 were infested; and of the Hawaiian,
8 were infested.

The following results were obtained from seeds planted in
seed-beds: Twelve seeds each of the Chutney and “Number 1”
were selected at random, and of the former, Io were infested.
Of the latter, 3 were infested. All of the infested seeds had
failed to germinate. In both instances the Chutney variety
showed the largest number of infested seeds.

The injury is much greater this season than last. The writer
estimates that fully 80 to 90 per cent. of the mangoes are in-
fested this year in what was considered the infested district last
year. Where the weevil occurs for the first time this season, the

infection is not so great. Not more than a single specimen was

2

observed within a seed last year. As many as four larvae have
been found within a single seed this season and two and three
specimens within a seed are common. Where as many as three
or four larvae occur within one seed, the resulting decay from
the excrement and seed extends through the husk, in some in-
stances, to the flesh. Some growers are of the opinion that the
work of the weevil hastens the maturity of the infected fruit and
increases the percent. of fallen mangoes.

ITS NATURAL ENEMIES

No parasitic or predaceous enemies of the mango weevil have
been observed. The writer believes, however, that many of the
hibernated weevils are destroyed by lizards and centipedes.

ITS CONTROL

Natural Control: Since the mango weevil is a special feeder
on the seed of the mango, its numbers in any particular season
are in direct proportion to the size of the mango crop for that
season. That is, when the mangoes are abundant, the brood of
weevils arising from the fruit will also be large in numbers. Any
natural condition of climate or disease that affects the mango
crop will likewise reduce the numbers of the mango weevil.

Direct Measures: The fact that the weevil during its entire
development is within the seed renders the use of any insecticide
impossible in combating the pest. Since also there is practically
no exterior evidence that the fruit is infested, little can be done
in the destruction of infested fruit during the growth of the
crop.

The destruction of all fallen mangoes and refuse seeds will be
quite effective for the reason that the adult beetle does not leave
the seed until some time after the maturity of the fruit.

The burning of all refuse about the mango trees during the

10

months from October to March would destroy many of the hiber-
nated weevils.

To deprive the mango weevil of its food in any particular
locality for two seasons would mean its extermination in that
locality, and could re-invasion be prevented, it would further
mean freedom from injury to future crops. An act worthy of
the attempt would be to destroy for a period of two years all the
fruit in the infested district after first making a careful survey
of the distribution of the weevil. Neglected trees in deserted
places and along the wayside could be cut down. All the com-
mon varieties could be cut back for in-arching or grafting with
the finer varieties. The finer varieties, of which not a great num-
ber are under bearing, could be allowed to fruit and the fruit or
refuse seeds destroyed. Certain trees should be left to fruit
throughout the infested district to act as “bait” for the weevils.
These trees should be under the control of inspectors and the
fruit gathered and destroyed after the weevils of the previous
season’s brood had completed copulation and oviposition.

The limited time of the writer has been devoted almost entirely
to the life-cycle and habits of the pest, necessary information on
which to base methods of control, and concerning which practi-
cally nothing could be found. Another season’s observation will
be necessary to advance more definite advice on the control of
this insect enemy of the mango.

Honolulu, H. T., August 14, 1906.

it

REFERENCES TO THE MANGO WEEVIL (Cryptorhyncius mangiferae)

IN HAWAII,

Van Dine, D. L.: Pacific Commercial Advertiser, Honolulu,
August II, 1905, p. 3.

Van Dine, D. L.: “The Mango Weevil in Hawaii,” Hawaiian
Forester and Agriculturist, Vol. II, No. 8, Honolulu, 1905, pp.
2at- 233. |

Kotinsky, Jacob: “Entomological Notes,’ Hawaiian Forester
and Agriculturist, Vol. II, No. 9, Honolulu, 1905, p. 266.
Van Dine, D. L.: “Introduction of the Mango Weevil,’ Ha-

waiian Forester and Agriculturist, Vol. Il, No. to, Honolulu,
1905, PPp- 313-315.

Van Dine, D. L.: Report of the Entomologist, Report on
Agricultural Investigations in Hawaii for 1905, U. S. Dept. Agr.,
Office of Experiment Stations, Bul. No. 170, Washington, 1906,
Pp. 47, 48.

Higgins, J. E.: “The Mango in Hawaii,” Bul. 12, Hawan
(U. S.) Experiment Station, Washington, 1906, pp. 24-25.

Craw, A.: Pacific Commercial Advertiser, Honolulu, June
21, 1906, p. 6.

Craw, A.: Hawaiian Forester and Agriculturist, Vol. III, No.
7, Honolulu, 1906, pp. 198, 199.

GAZETTE, HONOLULU
1906