Managing Rootworm Larvae With Soil Applied in Furrow Insecticide Treatments, 2017 Open Access

Corn rootworm (NCR/WCR) management efficacy trials were conducted to evaluate liquid and granular insecticide treatments near Bryant and Cavour in South Dakota. Experimental plots were arranged in an RCBD with four replications consisting of four rows (~50 ft long, spaced 30 inches apart). Granular and liquid insecticides were applied in the open seed furrow ahead of trench closer wheels. Planting-time liquid insecticides were applied using compressed air delivery systems to each row of the planter. These insecticides were mixed with water or 8-24-4 liquid fertilizer and applied at 5gal/acre. Granular insecticides were applied using a computer-assisted Smartbox insecticide delivery system. All metering units were calibrated on a four-row Kinze corn planter before treatment applications. Nonrootworm-resistant hybrids evaluated in this efficacy trial in 2017 included Pioneer P9526AM at the Bryant location and Syngenta/NorthrupKing N31H3220EZ4 at Cavour. Corn seed was planted at a rate of ~ 31,000 kernels per acre. Six roots per replication were dug randomly from the two outer rows, washed, and rated using the Oleson 0 to 3 root node injury scale (NIS). Yield assessments in bushels per acre were taken from the center two rows. Yield and root rating data were analyzed using the PROC MIXED/PDIFF option with Saxton’s lettering macro in SAS (version 9.2).

Corn rootworm node injury damage greatly exceeded the ~0.25 EIL at the Bryant (2.79) and Cavour (1.73) sites in the untreated control corn plots.

Due to extremely high root injury scores in the untreated control at the Bryant location, some insecticide treatments failed to prevent root injury scores from exceeding the 0.25 EIL (Table 1).

Treatments exceeding 0.25 EIL were Capture LFR (0.34), Capture 3RIVE 3D (0.39), Ethos XB (0.32), and Termitry LFR (0.31). Root injury scores were lower at the Cavour site, where the untreated checks scored 1.73 (1.6 nodes of damage less than at Bryant). All insecticide treated plots at Cavour scored 0.25 NIS or less. The Capture LFR-treated plots at Bryant yielded 30.6 bu/acre more (P = 0.0115) than the untreated controls. Yield from the other insecticide-treated plots was not significantly different from the untreated (8.9 to 18.9 bu/acre higher than the untreated controls). The Capture 3RIVE 3D insecticide treatment at Cavour had 23.7 bu/acre greater yield than the untreated controls (P = 0.0160). The yield from the Cavour site was greatly reduced by abnormally dry conditions that started in May and continued through the middle of July. This site averaged 82.5 bu/acre less than the field at Bryant that received slightly above average rainfall during the season.

A portion of this research was supported by USDA–NIFA and industry gifts.