PECAN NUT CASEBEARER CONTROL
by Jerry Parsons, Ph.D.
Horticulture Specialist, Texas Agricultural Extension Service
in San Antonio
The pecan nut casebearer is the number one insect
threat to pecan production in Texas. This nut feeder can account
for significant crop losses over many years on unsprayed trees.
With proper timing of a labeled insecticide, economic losses
can be minimized for commerical pecan producers. For homeowners,
spraying may be too expensive and, luckily, unnecessary.
In some seasons when pecan production is expected
to be heavy, the nut damage and consequent nut abortion caused
by the casebearer is beneficial to avoid over-production.
Too many pecans on a tree can cause limb breakage and poor
quality nut production. Pecan trees are alternate-bearing
which means the trees produce a heavy crop one year followed
by a light-to-non-existent crop the next year. During what
is expected to be a heavy crop year is when you need the casebearer's
"help" to thin the crop to prevent tree damage and
improve the nut quality.
Normally, this insect is found damaging nuts
within a two week period in May. This two-week time frame
will normally occur around the first week of May in South
Texas, the second week of May in San Antonio and South Central
Texas, and the third week in May in the Hill Country.
If you want to attempt to control this insect,
the timing of the insecticide application so crucial to effective
casebearer control is signaled by the appearance of hatched
eggs. Insecticides currently labeled for the casebearer do
not kill the eggs. They only kill larvae that feed on treated
leaves, buds and nuts. An insecticide applied before larvae
hatch will not work unless the residual lasts until the larvae
finally hatch. Since the larvae hatch over a week-long period
or more, a second application is recommended 7 days after
To determine when to spray, inspect pecan clusters
for casebearer eggs. Casebearer eggs will be located on the
puffed end of the young pecan nutlet. The egg will resemble
a small grain of sand.
Tag clusters that have eggs. Return to those
eggs daily until the first egg hatches. Once the egg is laid,
it will gradually turn from white to red in a three to five
day period before it hatches.
After hatching, the larva feeds on developing
buds and shoots for two to three days before entering a nut.
Apply your insecticide so that you have coverage on your trees
by the third day after the first egg hatching. By using this
method of timing, you will obtain the full residual effect
of your insecticide treatment.
A variety of pesticides can be legally used
on the pecan nut casebearer. Among those recommended are Sevin
and Malathion. Sevin and Malathion are familiar vegetable
garden insecticides and are effective controls for the pecan
casebearer if timely applications are made.
When spraying to control this damaging pest,
be sure to add zinc and the fungicide benomyl (systemic fungicide)
to the mixture. This will prevent leaf rosette and fungus
scab damage. Zinc must be applied as a spray on foliage to
be effective, since zinc soil applications are quickly rendered
unavailable for plant uptake in alkaline soils. The wet-able
powder zinc sulfate or a liquid formulation can be used. Zinc
sulfate sprays should not be applied close to peach or plum
trees since defoliation can occur. If peach or plum trees
are growing near pecan trees, a liquid formulation of zinc
must be used and will not cause any defoliation if mixed according
to label instructions.
Insecticide and fungicide can be mixed in the
same spray. If zinc sulfate is used, it is better to mix and
spray the zinc source in a separate application.