Tuesday, August 20, 2019

Spraying for pecan weevil

   I was up at 4:30 am this morning to spray my pecan orchard before the sun came up and it got too hot to achieve good spray coverage. My aim was to make sure pecan weevils weren't able to lay eggs in any of the pecans.  Pecan weevils (pictured above right) are "snout" beetles that can puncture the shuck and shell of a pecan to lay eggs inside the nut. The result are legless worms that devour the entire nut kernel.

    A key behavior of pecan weevil females is that will not start laying eggs until the nuts enter what is commonly known as the gel stage. The photo at left shows a 'Gardner' pecan that I cut open this morning. The kernel cavity is still largely filled with liquid endosperm but, just inside the kernel seed coat, a gelatinous layer of pecan kernel has begun to form. This translucent tissue is what we call the gel stage.
    With the soil moisture at near capacity, I  knew weevils had already begun to emerge and  would be ready to start laying eggs. Today promised to be sunny but very hot, so getting an early start on spraying was critical. I like to finish spraying for the day before the temperatures rise above 85 degrees F.
    When I first started spraying it was still dark. With all the tractor lights on, I could see just enough to navigate down the rows of my pecan breeding plot. However, spraying in the early morning hours has its advantages. The humidity is highest at this time of day which allows the mist created by the sprayer to travel further though the air. Before long, the first hints of dawn allowed me keep spraying without fear of getting lost in a maze of tree trunks.
   In 10 to 14 days, I'll need to spray again for late emerging weevils.