Tuesday, December 27, 2016

More than black spots on pecan kernels

   Over the past several years we have been making a special effort to prevent stink bugs from feeding on our nut crop. For the most part we've been fairly successful. However, we didn't start our stink bug control program early enough in the season to prevent black spots from developing on the kernels of very early ripening cultivars. The photo at right shows several Osage pecans damaged by stink bug feeding. As a very early ripening cultivar, Osage enters the dough stage at least a week before many of our standard northern pecan cultivars (Kanza, Pawnee, Major, Giles etc.). To prevent this type of kernel damage on Osage, we should have made a late July pesticide application in addition to our normal stink bug prevention program that begins during the first week of August.
    Stink bug feeding can cause more than just black spots on the kernels. Note the pecan in the lower right portion of the photo. A red arrow points to a large blackened area on a kernel half. When stinkbugs feed on pecan kernels, their digestive fluids kill a portion of the kernel leaving behind the characteristic black spot. However, during feeding, the stink bug can also introduce bacteria or fungi inside the shell. These organisms break down kernel tissue and cause large areas of the kernel to turn black. Ultimately, controlling stink bugs will prevent both types of kernel damage pictured above.