Alfalfa production as influenced by pest stress and early first harvest in Oklahoma

Abstract

Alfalfa forage yield, stand persistence and root total non-structural carbohydrate (TNC) reserves under variable first-harvest schedules were investigated with or without pest stress during a 4-year period in Oklahoma. Combined stresses due to weeds, alfalfa weevil and aphids reduced alfalfa forage yield in three cultivars by some 2 · 1 t/ha with significant reductions in OK08 and Arc, but not in WL 318. In addition, combined stresses significantly reduced stand persistence and TNC reserves. No significant cultivar x pesticide, cultivar x harvest schedule, or harvest schedule x pesticide interactions occurred. These data suggest that pesticide applications did help to preserve alfalfa stands and productivity. The need for such applications was much less in the pest-resistant cultivar WL 318. Early bud harvesting did not consistently result in reduced productivity of alfalfa relative to other harvest schedules, regardless of the cultivar being analysed or the pesticides applied.