Are Insecticidal Seed Treatments and In-Furrow Insecticides Worth It in Corn?
Are insecticidal seed treatments and in-furrow insecticides worth it in corn? Our evidence from North Carolina is mixed. The reason for this is that we cannot always predict when soil-dwelling insect pests will feed on corn and we don’t have great data sets to answer the question. So how can you go about deciding what to do?
All corn will come with some base-rate of insecticidal seed treatment, which will very likely be a neonicotinoid-class insecticide. We recently analyzed a data set from the highest-yielding corn farmers in the state. Our analysis was inconclusive as to whether or not insecticidal seed treatments were valuable (publication here). But these high-yielding fields likely had low insect pressure to begin with.
My gut feeling is that, a seed treatment at a lower rate (250), will probably pay on average in Coastal Plain and Piedmont fields. Since soil-dwelling insects (most commonly the grub and wireworm complex in our state) are so difficult to predict, the rare year where they occur can be very costly. In high pressure situations, our data show a clear benefit to higher rates of seed treatments (500 and 1250) for any soil-dwelling insect pest we test with.
Other locally important pests, including sugarcane beetle (sporadic in the Piedmont) and billbugs (Blacklands), are best managed with Poncho 1250. Blackland growers between the Albemarle and Pamlico Sounds should note that the efficacy of Poncho for billbugs has been declining over time. We don’t have a good labeled insecticidal remedy to solve this issue yet.
Note that a new product has recently entered the marketplace- Lumivia. This product is unique in that it is a new active ingredient (chlorantraniliprole, belonging to the diamide class of insecticides) paired with Cruiser 250. It works well for the grub and wireworm complex and is moderately effective for billbugs.
Bifenthrin in-furrow has been increasing in popularity. It can provide a good replacement for a seed treatment for the grub and wireworm complex. It is also could provide some resistance management benefit, since it is a pyrethroid and not a neonicotinoid.
We have not seen a benefit for sugarcane beetle or billbugs using bifenthrin alone compared to a seed treatment or with a seed treatment. As an exception, in a single study, billbug larvae number were reduced in the crowns using bifenthrin in-furrow. However, in general, Poncho 1250 without bifenthrin in-furrow is adequate in high-pressure situations for soil-dwelling insects.