ASSOCIATION BETWEEN SUGAR-BEET ROOT YIELD AND SUGAR-BEET ROOT MAGGOT (DIPTERA, OTITIDAE) DAMAGE

Sugarbeet root maggot, Tetanops myopacformis von Roder, is a major ins ect pest of sugarbeet throughout much of North America Root maggot dam age is routinely rated on a 0 (no damage! to 5 (severe damage) scale. In 42 trials, the relationship between visual damage and root yield wa s examined. The mean damage rating in the absence of insecticides was 3.3 +/- 0.4, compared with 1.7 +/- 0.7 for the highest yielding treatm ent in each trial. Mean root yield of the highest yielding treatment i n each trial was 48.8 +/- 8.9 Mg ha(-1), compared with a mean of 29.0 +/- 12.5 Mg ba(-1) when no insecticides were applied. Regression analy ses within individual trials indicated that the yield loss associated with each increment of the damage rating scale fluctuated widely, rang ing from near 0 to 15.7 +/- 2.42 Mg ha(-1). The percent yield reductio n in the absence of insecticides ranged from 9.8 to 83.6% when compare d with the treatment providing the most effective control in each test . These results are useful in estimating losses, developing recommenda tions, and providing a standard of comparison for alternative control strategies.