1998 ESA North Central Branch Meeting Abstract
63 USE OF ECONOMIC THRESHOLDS AND CORN ROOTWORM MANAGEMENT: AN EXERCISE IN FUTILITY? M. Gray, and K. Steffey. Department of Crop Sciences, University of Illinois, Champaign, Urbana, IL 61801
The relationship between corn rootworm larval injury and corn plant response has been examined by several entomologists. In the early 1970s, an initial relationship between root injury and yield loss was established, to date, only slight improvements in the original economic injury index have been made. In the late 1980s and early 1990s, researchers continued to more intensively quantify the relationship between rootworm larval injury and reductions in vegetative biomass, stalk lodging, corn nutrient content, above ground dry weights, gas exchange parameters, vegetative and reproductive biomass accumulations, and nitrogen deficiencies. In an effort to evaluate the meaningfulness of the economic injury index for corn rootworm larval injury, a 4-year field investigation to examine the compensatory root regrowth responses of 12 commonly grown maize hybrids was conducted at two locations in Illinois. Root injury ratings, root volume measurements, and root regrowth parameters were evaluated for their usefulness in predicting yield. Root ratings were as useful in predicting yield as root volumes and root regrowth measurements. Also, results indicate that root ratings well below 4.0 (one node of roots or the equivalent destroyed) can contribute to economic losses. These results clearly differ from other published reports that suggest root ratings of 4.0 to 5.0 (two nodes of roots or the equivalent destroyed) are necessary before soil insecticides are of economic benefit.
This paper will be presented on Monday.
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