Tuesday, January 14, 2014

Stinkbugs create a nasty suprise

Leaf-footed Bug
    This past fall the Kanza trees I planted near my home produced their first big crop of pecans. So many nuts in fact that the wife and I decided to harvest the nuts for our own use. Yesterday, I finally got around to cracking our Kanza crop and was disappointed by the number of nuts that had been attached by stink bugs. However, the amount of damage I found was very typical for back-yard, unsprayed pecan trees. There are numerous species of stink bugs and leaf-footed bugs (photo at right) that feed on pecans but all species leave behind bitter-tasting, black spots on the kernel. 
    The photo at left illustrates the type of damage I found caused by stink bugs. The nut on the far left was attacked during the water stage of nut development causing nut fill to cease and the entire kernel to become black and papery. The three other nuts were attacked after the nut had entered the dough stage. Each black spot on the kernel represents a stink bug feeding site.
    Stink bugs are a serious problem for back yard pecan growers. At the Pecan Experiment Field we use pesticides and an air-blast sprayer to keep these kernel feeding pests at bay. But these restricted-use pesticides and the equipment needed to apply them are generally not available to to the small scale pecan producer.  Carbaryl insecticide is widely available to home-owners and is recommended for use to control pecan weevil.  Carbaryl sprays, aimed at pecan weevil, will help reduce stink bug injury but will not eliminate the problem.
    You will notice that the amount of stink bug damage will vary widely from year to year. This is largely due to weather patterns that influence insect populations and the availability of alternative host plants for stink bugs to feed and reproduce.
    One thing is for sure, I'll be picking out a lot of stink bug damaged nuts while I'm shelling out the Kanza nut I picked up at home.