These soft-bodied insects appear during the summer and fall. They suck
the sap from the leaves, causing them to turn yellow or brown and fall
to the ground. Heavy infestations may cause defoliation in the late
summer reducing the nut crop in the current and succeeding year.
The black pecan aphid, _Melanocallis caryaefoliae_ (Davis), is about
one-sixteenth inch long when full grown, robust and greenish black. Its
back is decorated with tubercles.
Bright yellow blotches up to one-fourth inch in diameter appear around
the punctures produced by the feeding of this insect.
The yellow aphids, _Monellia_ spp., which attack pecans inflict injury
similar to that caused by the black pecan aphid. However, the large
yellow blotches on the leaves do not result from their feeding. A sticky
substance called “honeydew” is secreted by these insects creating an
ideal medium for sooty mold fungus to develop[5].
Both black and yellow aphids overwinter in the egg stage in crevices in
the bark. In the spring the eggs hatch, and the aphids begin feeding on
the leaves. Many generations are completed each year. Only females,
which may be wingless or winged, are produced during the growing season.
The winged individuals fly to different parts of the tree or to other
trees. In the fall, males and females appear and eggs are deposited
under the bark.
[Illustration: Figure 13. Pupa of the second generation of the pecan
nut casebearer in a hollowed out nut.]
Usually, these insects are not present in sufficient numbers to cause
serious injury until mid or late summer. Infestations earlier in the
season rarely assume damaging proportions. As is the case with mites,
aphid populations may increase, following the application of certain
insecticides applied for the control of the pecan nut casebearer or
following treatment with bordeaux mixture for pecan scab disease
control.
[Illustration: Figure 14. Southern green stink bug on developing
nuts.]
_Control._—When damaging infestations appear, the trees should be
sprayed with either 1 pound of 12 percent gamma BHC wettable powder; or
1 pint of 40 percent nicotine sulfate plus 3 pounds of soap; or 1 pound
of 25 percent parathion wettable powder[9].