Efficacy of selected insecticides on soybean looper in soybeans, 2023

Soybean was planted on 19 June on Portsmouth’s fine sandy loam near Plymouth, North Carolina. Plots were 40 by 12 feet with 4 replicates in a randomized complete block design. The insecticide treatments indicated in Table 1 were applied to all 4 rows of soybeans at growth stage R2-R3 on 22 August using a JD 6000 sprayer with plot boom calibrated 12 GPA, 3 MPH, and 50 PSI, using TX-6 hollow cone nozzles (2 per row). Soybean looper population density samples were taken with 2 black beat cloths (5-row feet each) from the middle 2 rows at 2, 7, 13, and 21 DAT. Data were analyzed using PROC MIXED (SAS 9.2), with treatment as the fixed effect and replication and the interaction of replication and treatment as random effects. Means were separated using Fisher’s protected LSD, and treatment differences were considered significant if P < 0.05. Data were transformed, as needed, to satisfy the assumptions of the model.

At 8 DAT all treatments had significantly lower soybean looper numbers than the untreated check. Among the insecticide treatments, plots with Plinazolin 200SC (4.0 oz) had the highest soybean looper numbers. Among the insecticide treatments, Plinazolin 200SC + Acephate 97S (4.0 oz + 0.75 lb) had the lowest soybean looper numbers. At 15 DAT Elevest 2.22SC (6.8 oz) and Steward 1.25SC (6.0 oz) had similar soybean looper numbers to the untreated check, with significantly lower numbers in all other treatments. Among the insecticide treatments, Steward 1.25SC + Acephate 97S (8.0 oz + 0.75 lb) had the lowest soybean looper numbers. At 22 DAT there were no significant differences among treatments.¹

Footnotes