Abstract
The sugarcane aphid, Melanaphis sacchari (Hemiptera: Aphididae) (SCA) affects grain sorghum, Sorghum bicolor (Poaceae) production. The response of sorghum hybrids to SCA was evaluated during 2017 in Guanajuato, Mexico. Experiments were established under strip-plot designs with two factors (hybrids, threshold-based chemical management -TBCM- treatments) and under irrigated or dryland conditions. Experiments were established on two sowing dates at Celaya and Valle de Santiago (irrigated) using the SCA-tolerant hybrids APACHE, BRS-70, MEZQUITE, SCAP-618, and SCA-susceptible UPM-219. Dryland experiments were established at Celaya, Valle de Santiago, and Pénjamo using MEZQUITE, and SCAP-618 (tolerant), and lines UPM-219, SHORTER, and MAJESTIC-355 (susceptible). The TBCM strategies were a) with TBCM (seed treatment with thiamethoxam; flupyradifurone or sulfoxaflor applied to foliage), and b) without TBCM (control). Significant differences (p < 0.05) between treatments under irrigated and dryland conditions for the number of aphids per leaf and grain yield were found. APACHE, BRS-70, and MEZQUITE had the highest grain yields under both TBCM and no-TBCM. UPM-219 was competitive under TBCM conditions, but without TBCM showed total yield losses. The yield–aphid cumulative density linear regressions were negatively significant (p ≤ 0.05) to sorghum cultivated without TBCM. Irrigation increased 64 % grain yields compared with dryland experiments. TBCM increased grain yield (50 % in irrigated and 100 % in dryland conditions). TBCM increased grain yields and reduced cumulative SCA populations under irrigated or rainfed conditions, mainly for susceptible sorghum. Resistant germplasm and TBCM could control SCA in sorghum cultivated in Guanajuato, mainly at late sowings frequently carried out under dryland conditions.