Influence of Tillage System and Irrigation Timing on Susceptibility of Three Cotton Cultivars to Tarnished Plant Bug – Year Two

Cotton production practices that impact pace of square production in early season and/or prolong availability of squares in late season will affect host finding, feeding, ovipositional preferences, and survival of tarnished plant bugs (Lygus lineolaris (Palisot de Beauvois)). Will such factors change the relative level of host plant resistance (HPR) of cotton cultivars? In this second year of research, we repeated two field experiments to evaluate how conservation tillage practices or irrigation initiation timing might affect plant bug abundance and damage in cultivars that have exhibited varying levels of HPR. Field studies were carried out on the Judd Hill Foundation Research Farm near Trumann in NE Arkansas. We compared performance of three early maturing cultivars with relatively high, medium and low HPR levels: Stoneville 5288 B2RF, Deltapine 0912 B2RF and Phytogen 375 WRF, respectively. Cool wet weather affected early season plant development in 2014. For both trials, fewer plant bugs were observed in the more resistant Deltapine 0912 and Stoneville 5288 cultivars compared to Phytogen 375 for which infestation levels were above action thresholds earlier in the season and for longer periods of time. Plant bug infestations reduced yield (P<0.05) for all cultivars in unprotected subplots in the tillage trial; however, plant bug damage did not result in consistent yield reductions in the irrigation study (P=0.12). Irrigation timing affected yield with lower yield in rainfed treatments compared to delayed irrigation initiation; highest yields were observed with early initiation. Neither tillage nor irrigation practices appeared to negatively impact host plant resistance levels among the resistant cultivars in 2014. Expanded understanding of HPR tolerance and resistance mechanisms will enable crop managers to make more efficient use of this important cultural control tactic within the framework of integrated pest management.