Efficacy of Seed Treatment and In-Furrow Insecticides for Southern Corn Billbug in Corn, 2024

We planted corn on 17 April 2024 on Portsmouth fine sandy loam near Salem, NC, to test selected in-furrow insecticides for efficacy against southern corn billbug. Our plots were 4 rows wide by 40 feet long, with 4 replicates in a randomized complete block design. We applied the insecticide treatments indicated in Table 1 to all 4 rows of corn at planting. We applied the liquids with the planter streamed in-furrow out of a 1/8-inch tube at 30 PSI and 10 GPA to direct the liquid onto the seed. We applied Counter using an inverted jar with a hole size in the lid calibrated to achieve the desired at-planting rate. Poncho was applied as a seed treatment and all seed had a fungicidal seed treatment. We took stand counts (representing the number of plants per 80 row-feet) and injury assessments (number of billbug-damaged plants per 80 row-feet) on 21 DAT and conducted injury assessments again on 28 DAT. We evaluated yield by harvesting the 2 middle rows of each plot on 27 August 2024, adjusting weights by 15.5%. We analyzed data using a mixed model 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 21 DAT, injury levels were significantly lower in plots treated with Poncho (1.25 mg AI/seed), Poncho (0.5 mg AI/seed), and Poncho (0.5 mg AI/seed) + Counter (6.5 lb/acre) compared with the untreated check (Table 1). At 28 DAT, injury levels were significantly lower in plots treated with Poncho (1.25 mg AI/seed) or Poncho (0.5 mg AI/seed) compared with the untreated check. We observed significantly higher yields in plots treated with Regent 3.2 oz compared with the untreated check.¹

Footnotes