Biological Control of The Western Corn Rootworm Using an Entomoparasitic Nematode, 1992

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 30 rows of 10 (76-cm row spacing, planted 19 May), were infested on 9 Jun with 800 WCR eggs/30.5 cm of row. Sixty additional plants were infested to monitor WCR development. Most plants had reached the 2-leaf stage when infested; 20% were at the 1-leaf stage. A factorial design was used, testing nematode application rate and timing of application relative to WCR development. Nematodes (BioVector®) were applied on 4 dates, determined by rootworm development: before hatch (18 Jun), and when the population had reached its early 1st (29 Jun), 2nd (8 Jul), and 3rd instars (15 Jul). Fourteen ml of 0.15% agar S. carpocapsae suspension was applied around the base of treated plants with a 35 ml syringe. Four replicates of 4 nematode rates and an agar control were applied on each date. Soil conditions were highly favorable for nematode movement except for 8 Jul, when the plots were watered to ensure the top 10 cm of soil was uniformly moist. On 31 Aug, 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).