earlier post, the black spots found on pecan kernels are the result of feeding by stinkbugs and/or leaf-footed bugs (photo at right).
Last year (2010) we found quite a bit of stink bug damage. This year (2011) the number of kernels with black spots are far fewer. I wish I could come up with a good explanation for the year-to-year variation in stink bug damage but it turns out that the movements and population numbers for this group of plant feeding bugs are very hard to predict.
Over the past several years, our control strategy for kernel feeding bugs has been to apply an insecticide (Warrior II) in early August. Subsequent insecticide applications aimed at pecan weevil also help decrease stink bug populations. These control measures are not perfect but seem to keep kernel damage down to less that 1% of kernels.