A quick walk out into the pecan orchard at this time of year and you might spot several green nuts on the ground. A quick look at the fallen nuts and you will probably find some scab lesions or large patches of discolored shuck tissue.
However, the primary reason these nuts have dropped during the first week of August is stinkbug feeding. It is often difficult to identify stinkbug damage by inspecting the exterior of the shuck. If you look carefully, you might find stinkbug feeding scars on the outside of the nuts but, with numerous scab lesions also present, these small feeding scars might be hard to see.
The easiest way to confirm stinkbug feeding is to cut open dropped nuts and inspect the developing kernel. If the interior of the nut including the developing kernel is dark brown you can be assured that stinkbugs have attacked the nut.
This morning we received nearly 2 inches of rain which should stimulate the emergence of pecan weevil. These weevils will also start feeding on nuts causing a nut drop similar to the drop caused by stinkbugs. You can distinguish weevil feeding from stinkbug feeding by the size of the hole drilled through the shuck. Weevils make a much larger hole in the shuck and often leave a pattern of foot marks around the feeding site. Weevils will continue to feed on nuts until kernels reach the dough stage.
Once this rain system passes all the way through our area, we plan to spray our pecans to control the stink bug population and kill off early emerging pecan weevils.