|Anderson, A - NORTH DAKOTA STATE UNIV|
|Dregseth, Robert - NORTH DAKOTA STATE UNIV|
|Smith, Larry - UNIVERSITY OF MINNESOTA|
Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 29, 1997
Publication Date: N/A
Interpretive Summary: Sugarbeet root maggot is the major pest of sugarbeet in Minnesota and Eastern North Dakota. The primary control method has been the use of planting-time insecticides directed towards reducing larva populations in sugarbeet fields. This reports summarizes the variability of effectiveness of commonly used control measures and examines the relationship between visual damage ratings and yield loss attributable to root maggot damage. Forty-two insecticide trials conducted over a 10 year period at five locations provided a large number of environments for observation. Differences in observable damage were reflected in corresponding yield differences. Root yield differences between the most effective control measure and no control ranged from 2.8 to 15.3 tons/acre with an average yield difference of 8.8 tons/acre or a yield reduction of 42% when the absence of control is compared to the most effective control. These results are useful in estimating losses, developing recommendations, and providing a standard of comparison for alternative control strategies being pursued at this laboratory.
Technical Abstract: Sugarbeet root maggot (Tetanops myopaeformis von Roder) is a major insect pest of sugarbeet throughout much of North America. Root maggot damage is routinely rated on a 0 (no damage) to 5 (severe) scale. Forty-two trials were utilized to examine the relationship between visual damage and root yield. The mean damage rating in the absence of insecticides was 3.3, compared to 1.7 for the highest yielding treatment in each trial. Mean root yield of the highest yielding treatment in each trial was 48.8 Mg ha(-1), compared to a mean of 29.0 Mg ha(-1) when no insecticides were applied. Regression analyses within individual trials indicated that the yield loss associated with each increment of the damage rating scale fluctuated widely, ranging from near zero to 15.7 Mg ha(-1). The percent yield reduction in the absence of insecticides ranged from 9.8% to 83.6% when compared to the treatment providing the most effective control in each test. These results are useful in estimating losses, developing recommendations, and providing a standard of comparison for alternative control strategies.