Field key to larvae in pecans

              Division of Agricultural Sciences and Natural Resources • Oklahoma State University
F-7163
Oklahoma Cooperative Extension Fact Sheets
are also available on our website at:
http://www.osuextra.com
Field Key to Larvae
in Pecans
Phil Mulder
Extension Entomologist
Don C. Arnold
Survey Entomologist
This key is designed to serve as a guide to identification
of the more typical larvae of the common insect species found
in pecans and on pecan trees in Oklahoma. The identifying
characters used are based upon those found on full-grown or
nearly full-grown larvae and may not necessarily occur on
newly hatched larvae. If the larva in question does not fit the
proper description furnished, recheck the specimen with the
key. If it continues to key out improperly or is not one of the
species listed, and proper identification is desired, place the
larva in a small bottle containing 70% alcohol and mail to:
Department of Entomology and Plant Pathology, Oklahoma
State University, Stillwater, Oklahoma 74078. Please do not
send specimens for identification unless they are causing or
suspected of causing damage to the crop. Please include
information as to the type and amount of damage noted as well
as the date and community where the larva was collected.
This information will assist in getting a more accurate and
rapid reply to your questions.
Some insects found on pecans cannot be identified with
this key. This would include adult insects, closely related
organisms, and such insects as aphids and phylloxera, which
do not have a larval stage. Be sure you have insect larvae
before attempting to use this key.
All insect larvae normally found on pecans are included
in this key. This key should be used primarily for larvae on
pecans, but should be moderately accurate for larvae on
walnut trees, also. Keys for other crops are available and can
be obtained from the local county Extension office.
Survey Methods
Most pecan insects should be reported as the number per
nut cluster or per tree. In the early season, the pecan nut
casebearer should be reported as the number of eggs or
larvae per 100 clusters. The color of the eggs should also be
reported. After the nuts set, the number of damaged nuts per
100 clusters should be reported. Depending on the size of the
grove, at least 50 clusters should be inspected. The hickory
shuckworm should be reported as the number of damaged
nuts per 100 nuts to give the percentage infestation.
Pecan weevil surveys are made by jarring the tree and
counting the weevils that fall. This is much easier if a light
colored cloth or plastic sheet is placed under the tree. This
should be reported as the number per tree or limb. Also, the
size of the tree should be reported. Larvae in the nuts should
be reported as the percentage of nuts infested. Adult emer-gence
can be checked with screen wire cages placed under
infested trees about mid-summer.
Leaf-feeding larvae should be reported as light if very
small numbers are present and little damage has occurred. If
noticeable damage has occurred, it should be reported as the
percentage of defoliation. The fall webworm can be reported
as the number and size of webs per tree and the percentage
of trees infested in the immediate area.
Descriptions of Larvae
Pecan Weevil Larvae (Curculio caryae)
These robust, dirty white, somewhat C-shaped larvae
are up to 5/8 inch in length when fully grown. The head is
yellow to brown. They are found in the nuts during late
summer and early fall and can be found in the soil beneath
infested trees during the rest of the year.
Pecan Nut Casebearer (Acrobasis nuxovrella)
The body color is pale borwnish-yellow to light gray
brown. The head is reddish-brown with deeper brown spots.
They are up to 5/8 inch in length when mature. Over-wintering
larvae feed on the buds and bore into young shoots in spring.
The first generation larvae attack the young nuts in late spring,
often webbing them together. Second generation larvae at-tack
larger nuts in early summer. A third generation occurs
later, but does little damage.
Walnut Caterpillar (Datana integerrima)
Young larvae are reddish with narrow yellowish or gray-ish
lines, which extend the entire length of the body. Mature
larvae are black with only two grayish lines on the back and
two on the sides. Many soft, fine, long, grayish hairs cover the
entire body. They may be up to 1 1/2 inches in length. They
feed on leaves, in groups, and do not form webs on the leaves.
There are two generations per year.
Fall Webworm (Hyphantria cunea)
These larvae vary from light buff to near black. They are
covered with long light-colored hairs. They may be up to
1 1/4 inches long when mature. They make large webs on the
trees and live and feed in them. There are two generations per
year. Some authorities recognize two species; H. cunea and