| dc.description.abstract | Sugarcane aphid, Melanaphis sacchari (Hemiptera: Aphididiae), was first detected on grain sorghum, Sorghum bicolor, in the United States in 2013. The spread of sugarcane aphid across the sorghum-producing regions of North America necessitated increased understanding of damage by and methods for mitigation of the pest. In response, field experiments were conducted to develop economic thresholds for sugarcane aphid. Grain sorghum yield—aphid population density relationships were used to calculate economic injury levels and economic thresholds. Economic injury levels ranged from 37 and 102 aphids per leaf, and an economic threshold of 40 aphid per leaf was deemed prudent to use across the observed range of hybrid, environmental, and market conditions. Subsequently, a tally-based threshold was considered by evaluating the infestation proportion – aphid density relationship for tallies of >25, >50, and >100 aphids per leaf. Regressions showed a second order polynomial relationship yielded decisions most similar to use of the density-based threshold. The tally threshold required half the time to sample 100 leaves compared to the density-based approach. With increased introduction of grain sorghum hybrids partially resistant to sugarcane aphid, field evaluations of the grain yield–aphid population relationship were conducted across growing seasons, locations, and hybrids believed to vary in aphid susceptibility. These data verified previously established economic injury levels ranging from 27 to 72 aphids per leaf for the most susceptible hybrids. For 47 of the 49 partially resistant hybrid location-years, yield loss attributable to aphid density was not detected under aphid densities up to 352 aphids per leaf. Population doubling time for sugarcane aphid on partially resistant grain sorghum hybrids was approximately two times that of susceptible hybrids. Finally, spray tips were evaluated for canopy penetration and coverage using grower spray equipment and two spray volumes. There were no differences in coverage among spray tips or between spray volumes. When guided by economic thresholds for susceptible hybrids, several configurations of spray equipment and volumes are effective. Overall, sugarcane aphid can be managed with use of partially aphid-resistant hybrids and aphid-susceptible hybrids with addition of insecticides applied with common grower equipment and guided by use of economic thresholds. | en |
