Sunday, August 22, 2021

Spraying for weevil control

     Its been a relatively dry summer this year so I decided to delay making my first weevil spray until after we got a good soaking rain. Well, during the early morning hours of August 21st we received our first good rain (0.96 inches) in several weeks. This rainfall event should allow pecan weevils to emerge from their underground cells and find their way to the nearest pecan nut cluster. The photo above shows both a female (longer snout) and male adult weevils.

   The first order of business for these insects is to move to a pecan nut cluster in the hope of finding a weevil of the opposite sex. After mating, the female will start puncturing pecans to discover if the nuts are suitable for egg laying. She will not deposit eggs inside the nut until the kernel inside has entered the gel stage.


    I cut several pecans open today and found that even early-ripening cultivars were still in the water stage (photo at left). As I mentioned in my previous post, pecan kernel development is much later than normal the year due to unseasonably cool Spring temperatures.

    The combination of a concentrated weevil emergence due a triggering rainfall event and a nut crop not ready for weevil oviposition means that weevils will just keep probing nuts until kernels start to firm up inside the shell. A pecan that gets punctured during the water stage will drop off the tree (both weevils and stink bugs cause nut drop).

    To prevent a possible significant amount of weevil induced nut drop, I decided to spray my orchard with and insecticide. In spraying the orchard, I started at dawn this  morning (22 Aug 2021) and quit around 10:30 am as air temperatures climbed above 85 degrees F. The forecast for tomorrow is afternoon temperatures in the mid 90's (F), so I'll be getting up early tomorrow morning to finish the job. 

    With cooler temperatures and high humidity, early morning is the best time for spraying. The water droplets that blow out of the sprayer stay airborne longer and do a better job at coating all the surfaces of the pecan tree's canopy. For this weevil spray I used Warrior II insecticide. I'll probably spray again in 10 to 14 days depending on soil conditions and rainfall patterns.