Impact of Selected Insecticide Seed Treatments and In-Furrow-Applied Insecticides on Field Corn Yield 1, 2018

The impact of selected insecticide seed treatments on field corn yield was evaluated at the Delta Research and Extension Center (Washington County). Corn seed (Dekalb DKC 67-57) were planted on a Dubbs silt loam soil on 22 Mar at a seeding rate of 34,658 seeds per acre. All seed were treated with a common fungicide treatment to minimize seed and seedling diseases. In-furrow spray treatments were applied with a CO₂-charged spray system through 2501 nozzles (1/row) mounted in front of the press wheels. The spray tips were turned to spray across the furrow and calibrated to deliver 5 gpa finished spray. Emergence date for the trial was 29 Mar. Plot size was four rows (40 in centers) by 50 ft. Treatments were replicated four times in a RCB. On 12 May plants expressing damage symptomology (wilting, stunting) were excavated to determine which insect(s) were present. Southern corn rootworm was the primary insect observed, along with some wireworms. Plant density was determined at 8 and 29 days after emergence (DAE) by counting all plants on the center two rows of each plot. Grain yield was determined by harvesting the center two rows of each plot with a small plot combine on 21 Sep. Yields were adjusted to 15% moisture content and converted to bu/acre. Data were subjected to ANOVA and means separated according to Fisher’s Protected Least Significant Difference.

All of the insecticide treatments resulted in higher plant density compared to the untreated check at 8 and 29 DAE (Table 1). Plots that received Dermacor (0.25 mg AI/seed), Poncho, Poncho plus Verimark, or Brigade plus Prevathon (14 oz/acre) had higher plant densities than plots that received Verimark (0.25 mg AI/seed) at 8 DAE. At 29 DAE Brigade plus Prevathon (14 oz/acre) resulted in greater plant density than Verimark (0.25 mg AI/seed). All of the insecticides resulted in higher yields compared to the untreated check. Also, plots that received Poncho plus Verimark, Poncho plus Dermacor, Brigade, or Brigade plus Prevathon (14 oz/acre) had higher yields than plots that received Verimark (0.25 mg AI/seed).¹

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