LAUSR

Abstract. Studies in the field and growth chamber evaluated sorghum, Sorghum bicolor (L.) Moench, hybrids for resistance to sugarcane aphid, Melanaphis sacchari (Zehntner). Hybrids were known resistant ATx2752/RTx2783, known susceptible ATx2752/RTx430, and 14 with suspected resistance. The field study was done during 2015 and 2016 at three locations in Louisiana. The study was a split-plot design with hybrids randomized to main plots and insecticidal protection from aphid infestation (sprayed versus non-sprayed) randomized to sub-plots. Seedlings of the hybrids also were evaluated in a growth chamber. In the field, hybrids that seemed susceptible (demonstrated yield benefit after application of insecticide) were ATx2752/RTx430 and DG M756B39. Hybrids with possible tolerance (many cumulative aphid days but no yield benefit from insecticide) were DG M77GB52, DG 765B, and R94153. Hybrids with possible antibiosis (few cumulative aphid days and no benefit from insecticide) were ATx2752/RTx2783, RS84353, RS9813, SP6929, SP73B12, SP7715, SPX760, SP78M30, 83P17, W-844-E, and DKS37-07. Seedlings of ATx2752/RTx2783, DKS37-07, RS9813, RS84353, SP7715, SPX17414, SPX17514, NKX760, and W-844-E were significantly less damaged by aphids feeding than was ATx2752/RTx430. In addition to field and seedling studies, four hybrids were used to evaluate reproductive potential of sugarcane aphids in a growth chamber. Suspected resistant hybrid DKS37-07, suspected susceptible hybrid M75GB39, and two intermediate hybrids P83P17 and W -844-E were used. DKS3707 was the most resistant hybrid evaluated, with reduced intrinsic rate of increase of sugarcane aphids compared to the other hybrids. M75GB39 seemed the most susceptible of the three hybrids.