Biological Control of the Western Corn Rootworm Using An Entomoparasitic Nematode, 1991

Efficacy of Steinernema carpocapsae, All strain as a biological control agent for WCR was evaluated on a Waukegan silt loam soil at the University of Minnesota Agricultural Experiment Station, Rosemount. Experimental plots, consisting of 30 plants in 3 rows (76 cm row spacing) of 10, were laid out in a completely random design on 28 Jun, and infested with WCR eggs at 600 eggs/30.5 cm of row using the method of Branson and Sutter (1980). Most of the corn (planted 10 Jun) had then reached the 3 or 4-leaf stage. On 17 Jul, nematodes (BioVector° were applied. Approximately 11 ml of S. carpocapsae suspended in 0.15% agar were applied around the base of each treated plant with a 35 ml syringe. Control plants received agar only. Six replicates of 4 nematode rates and an agar control were used; although applied per-plant, rates are expressed as nematodes/30.5 cm of row. All plots were watered after treatment until the top 5 cm of soil appeared uniformly moist. Three WCR emergence cages were placed in each plot on 24 Jul, each covering 2 plants. Beetle traps were monitored weekly from 31 Jul through 23 Sep. On 17 Sep, 10 roots from each plot were dug, washed, and rated using the Iowa 1-6 root injury scale (with half-point increments of greater sensitivity).