See below a note from Dr Rick Brandenburg at NCSU regarding southern corn rootworm in peanut. In general, Virginia has had less rainfall than what Rick is reporting from NC so our risk to rootworms is less, but his insigts are helpful.
From Rick Brandenburg, NCSU: The past week, I’ve received a lot of calls on a lot of different topics, but the most common question focused on southern corn rootworm. Many of the others were on worms in peanuts. The typical question, which was a very good one, focused on whether peanuts were at greater risk from rootworms this year due to the wet weather we’ve had recently and the fact that some of our peanuts are a little late. This is not information that shows up directly in the rootworm advisory, but the questions you ask show a great understanding of the index and the factors that affect rootworms.
Yes, the above normal rainfall is making rootworms more of a threat and even lighter, sandier soils could support rootworms with this kind of weather. So if you have a marginal field, the rains have probably moved the risk up a notch. We’ve got a lot of good looking peanuts out there and some of them are late. This lateness makes them at more risk from rootworms as well as the larvae prefer to attack the smaller, more immature pods. The word that I’ve been passing along is that if you have a good crop, the fields have been and remain on the wet side, and/or the crop is a little late, then the risk is higher than the index rating you will have. How much higher is a guess, but it is higher this year. Given the fact that the threat from spider mites seems minimal right now and that we’ve had quite a few leafhoppers out there, the use of Lorsban (chlorpyrifos) or a generic seems like a pretty good idea in many fields. Since it is about August 1, growers could consider going with a half rate.
Rootworm treatments are a bit of a guessing game each year, but the wet weather makes it a bit less, but no guarantees. I would hate to see some of these good peanuts we’ve got out there get dug this fall and have a lot of damage. That’s my personal judgment.