On the Biology and Control of the North American Chestnut Weevils
On the Biology and Control of the North American Chestnut Weevils
Loading...
Files
Publication or External Link
Date
1956
Authors
Johnson, Warren T.
Advisor
Cory, E.N.
Citation
DRUM DOI
Abstract
Curculio auriger (Casey) and Curculio proboscideus
Fab. are indigenous North American nut weevils and attack
only the fruits of chestnut and chinquapin. Their natural
distribution occurs over the same geographical areas that
the American chestnut was found. Since the destruction of
most of the native chestnut trees by chestnut blight,
Endothia parasitica (Murr.), the weevils have been able to
survive on scattered plantings of oriental chestnuts which
are resistant to blight, from a few native chestnut trees
partially resistant and from the coppice growth of old chestnut
stumps.
Rearing of both species in the field was accomplished
by the use of soil cages set into the ground to a depth of
12 inches. Adult behavior was studied in large cages that
completely covered the tree.
Chestnut weevils lay their eggs in the kernel. The
eggs of C. auriger hatch in about eight days and those of
C. proboscideus hatch in about 10 days under the conditions
in central Maryland. There are four larval instars in each
species and these are described and illustrated. Head
characters were found that will separate the species and the instars. C. auriger completes its larval development in 21
days while it takes 30 days for Q. proboscideus.
The pupae of both species are of' the exerate type and
may be separated by the presence of two small bristles on the
beak, near the insertion of the antennae, of C. auriger.
These bristles are lacking in C. proboscideus.
The usual life cycle of C. auriger is two years. The
life cycle of C. proboscideus is usually one year. A few
individuals of each species require an additional year to
complete their cycle. The adult C. auriger issues from the
ground in May and feeds on the chestnut catkins. After the
catkins wither they disperse and are not seen again until the
chestnuts are nearing maturity. C. proboscideus issues from
the ground late in July and may be seen in the trees a few
days after emergence.
The male genitalia were studied for taxonomic characters.
These characters are sufficiently clear so that the two chestnut
weevils may be identified thereby.
Two species of internal insect parasites were found.
Myiophasia nigrifrons Tns., a tachinid fly, was reared from
the larvae of both species of' chestnut weevils and was observed
in its larval stage within the body cavity of the chestnut
weevil larva. Urosigalphus armatus Ashm. is a braconid parasite
and was found only in the larvae of Q. prohoscideus.
Chemical control studies have shown that the adult
stage is the most susceptible to insecticides. Preliminary
tests with heptachlor, applied at the rate of six to eight
pounds of the chemical per acre, as a spray or dust to the
ground cover under the trees, have given excellent results
for the control of chestnut weevils.