Impact of True Armyworm (Lepidoptera: Noctuidae) Feeding on Wheat Yields in Arkansas

Abstract

Wheat leaf consumption by the true armyworm, Pseudaletia unipuncta Haworth, was determined in the laboratory in 1993, 1994, and 1995. Total mean wheat leaf area consumed per larva from eclosion to pupation varied significantly from year to year (77.4–135.4 cm2) with an overall mean leaf area consumed of 103.2 cm2. Wheat field plots were infested with third-instar armyworms and allowed to consume wheat foliage at boot and anthesis stages until preset defoliation levels were met (0, 10, 25, and 50% defoliation in 1993, and 0, 35, 50, 65, and 75% defoliation in 1994, and 0, 35, 50, 65, and 75% defoliation in 1995, and 1996). Overall, no significant differences were seen between treatments in number of heads or mean weight of seeds per head in any year suggesting that at boot and anthesis stages Arkansas wheat can sustain up to 75% defoliation by armyworms with little loss in yield. Even at population levels that resulted in 75% defoliation head cutting was negligible.