CULTIVAR RESISTANCE AND ARTHROPOD PREDATION OF SUGARCANE BORER (LEPIDOPTERA, PYRALIDAE) AFFECTS INCIDENCE OF DEADHEARTS IN LOUISIANA SUGARCANE

A 3-yr study on overwintering populations of the sugarcane borer, Diatraea saccharalis (F.), showed cultivar resistance provided significant reductions in numbers of sugarcane, a complex hybrid of Saccharum spp., deadhearts in the spring of 1986 and 1987. Although differences in infestation levels of D. saccharalis caused by arthropod predation were not detected in the fall, significantly greater numbers of deadhearts occurred in the spring where predators were suppressed. The red imported fire ant, Solenopsis invicta Buren (Hymenoptera: Formicidae), was the dominant predator in these studies. Incorporating a covariable representing the number of larvae infesting sugarcane stalks in the fall did not adequately account for the variation in sugarcane shoots with deadhearts. Results from this study indicate that, in addition to the anticipated effect of cultivar resistance and predation on the stalk damage caused by D. saccharalis during the growing season, substantial reductions in the incidence of spring deadhearts can also be expected. The effect of-cultivar resistance and arthropod predation of D. saccharalis on deadhearts is additive.