APHIDS
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.
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.
