Efficacy of At-Planting Insecticides for Thrips in Soybean, 2024

We planted soybean on 31 May 2024 on a Roper muck soil near Swanquarter, NC to test selected insecticide treatments for efficacy against tobacco thrips. Plots were 4 rows wide by 40 feet long with 4 replicates in an randomized complete block design. We applied the granular insecticide aldicarb (Table 1) in-furrow to all 4 rows of soybean at planting, while we treated the seeds in the appropriate treatments prior to planting.

We collected thrips samples by taking five random plants from the middle rows of each plot on 18 and 25 DAT. We washed and rinsed the plants, leaving nymphs and adults from each sample suspended in an ethanol solution. We later counted thrips from this ethanol under a microscope. We harvested the two middle rows of each plot on 5 November 2024 and adjusted weights to 13.5% moisture.

We analyzed data using mixed models ANOVA, with treatment as the fixed factor and replication and the interaction of treatment and replication as random factors. We used transformations, as needed, to satisfy model assumptions. Finally, we used Fisher’s protected LSD procedure for means separations.

At 18 DAT, the UTC had significantly higher nymph pressure than all other treatments. AgLogic (7lb/acre), Gaucho 600, and Ilevo (1.92 fl oz/140,000 seed) had the lowest nymph pressure of all treatments. At 25 DAT, Gaucho 600 and Ilevo (1.92 fl oz/140,000 seed) had significantly higher nymph pressure than all other treatments. AgLogic (7.0 lb/acre) had significantly lower nymph pressure than all other treatments. For both dates, there were no significant differences among adults. There were no significant differences in yield.¹

Footnotes