Tomato Spotted Wilt Peanut Notes No. 191 2022

At the CHROME field day I was asked about prevalence of TSWV in peanuts this year. A farmer was seeing more than he saw in 2021. I too have seen more than in the past. I'm seeing more fields with the up and down look in the canopy that can be associated with TSWV. We know that TSWV incidence can be up and down, and this has much to do with thrips populations (when they are most prevalent and numbers) and how effective we are in controlling them.  It was a short conversation, but this grower planted Bailey II around May 15. This variety and planting date are exactly what we often recommend and are two key elements of the TSWV index for NC. He used imidacloprid in the seed furrow at planting. We didn't go into much detail, but it would not be uncommon for there to be more injury from thrips (poor control) with this treatment compared to phorate or AgLogic. We are also seeing less control with imidacloprid now than 5 or 10 years ago. So, it is possible thrips were able to feed for a prolonged period of time because of marginal control and transmit more virus. Additionally, research in the southeast, where TSWV has historically been a major issue, has shown that you can have more TSWV after imidacloprid than when phorate is used or even compared with peanut not treated with in-furrow insecticide. Our relatively low levels of TSWV in recent years and resistance in Bailey II (and other varieties) have allowed us to use imidacloprid with minimal concern for increasing TSWV. We may need to reconsider use of this insecticide if TSWV incidence increases and poor control of thrips becomes more widespread.

We also are planting earlier to avoid as much damage from southern corn rootworm as possible. This puts us at greater risk for TSWV.