Impact of buckwheat and methyl salicylate lures on natural enemy abundance for early season management of Melanaphis sacchari (Hemiptera: Aphididae) in sweet sorghum

Abstract

Early in the growing season when pest densities are low, crop environments are often unattractive to natural enemies. A combination of flowering plants providing food and alternate prey and herbivore induced plant volatiles (HIPV) may attract and retain natural enemies in crops. Melanaphis sacchari Zehntner (Hemiptera: Aphididae), a new pest of sweet sorghum (Sorghum bicolor L.), causes significant yield loss if left unmanaged. In a three-year field study, we tested the extent to which buckwheat (Fagopyrum esculentum Moench) border strips and lures containing the HIPV methyl salicylate attracted natural enemies prior to and during M. sacchari establishment in sweet sorghum plots. Natural enemies were surveyed weekly within the sweet sorghum (visual counts and yellow sticky cards) and in buckwheat border strips outside the plots (vacuum sampling). M. sacchari visual counts and natural enemy surveys were performed until harvest. Within buckwheat border strips, natural enemies were more abundant relative to non-buckwheat border strips. However, the increase in buckwheat borders did not increase natural enemies within sweet sorghum plots. In addition, the most abundant natural enemies within sweet sorghum (Coccinellidae) were uncommon in buckwheat strips. Methyl salicylate did not impact natural enemies in sweet sorghum border strips. M. sacchari populations and sweet sorghum yields were not affected by treatments. Other methods of increasing natural enemies will need to be explored to enhance early season management of M. sacchari in sweet sorghum fields.