Friday, July 13, 2012

Summer nut drop

     During mid-summer, there are a few critters out there that can cause pecans to drop. This summer, we set up drop cages to collect dropped nuts so we can monitor the causes for nut loss. Here are a few of the nuts we've found.
    The pecan pictured at right fell from the tree after being attacked by the hickory shuckworm. The bright white spot on the outside of the nut identifies shuckworm as the reason for the drop.  After hickory shuckworm females lay there eggs in the husk of a pecan, they cover the site with some scales rubbed off from their lower abdomen. This results in a raised spot of what looks like white fluff. We see hickory shuckworm damage every July but damage levels are rarely large enough to warrant control measures.
      Stink bugs and leaf-footed bugs can cause mid-summer nut drop (photo at left). The tell-tale signs of activity for these kernel feeding bugs are two fold. On the outside of the shuck, you should see small black feeding scars as well as large areas of damaged husk tissue. Cut open the nut and you will find the internal portions of the nut stained dark brown to black. These insects are primarily a late season pests but this summer's drought has caused an early migration of bugs into pecan groves. Fortunately, we are seeing only low number of these kernel feeding insects at this point. I typically apply an insecticide in early August specifically aimed at controlling stink bugs and leaf-footed bugs.

     We found one surprising nut drop--a pecan half eaten by a squirrel (photo at right). Squirrels usually do not start cutting into pecans until mid-August, when kernels enter the dough stage. However, this extended drought must be putting a lot of pressure on the squirrel's normal food sources. This must also be the reason we have been having great success trapping squirrels over the last month--they are starving.
     Nuts that drop from drought typically look dried up (photo at right). The shuck is completely rock hard and dark in color. However, inside you will find that the developing kernel is still white. This is in contrast to the stink bug damaged nut that has a darkened kernel (above). Fortunately, we have not seen a lot of drought induced nut drop so far this year.