Monday, August 8, 2011

Stink bug nut drop

    During early August, several species of stink bugs migrate into pecans groves and start feeding on developing nuts. If a stick bug punctures a nut to feed on the kernel during nut enlargement, that nut will drop from the tree. In the photo at right, The red arrows point to puncture marks left after stink bug feeding. This nut was punctured 3 times (the upper red arrow points to two punctures very near each other). We found this nut in one of our drop cages that collect all the nuts that fall from the tree during the course of the season. It usually takes 3-5 days after the damage occurs for the nut to drop off the tree, so this nut was probably attacked by a stink bug late last week
     If you cut the nut open (photo at left), you will note that the developing kernel has turned dark brown to black. The yellow arrow points to the developing kernel that is less that 1/2 way to full water stage.
    In the photo, you will notice that the cut surface of the shuck has turned black. This occurs when shuck cells are exposed to the air and is not a sign of stink bug feeding. However, the darken areas inside the shell are the result of insect attack.
    This year the weather has been so dry that even stink bug populations seem suppressed. It may be that a total lack of succulent plant growth earlier in the season has made it difficult for stink bugs to  grow, reproduce, and build their population numbers. We'll be watching our drop cages for signs of increased stink bug activity.