Artificial infestations of beet armyworm, Spodoptera exigua (Lepidoptera: Noctuidae), used to estimate an economic injury level in tomato

Although beet armyworm, Spodoptera exigua (Hübner), can be a major pest of tomato in the Southeastern USA, relatively little is known about the direct relationship between beet armyworm feeding and tomato yield. An economic injury level (EIL) specifically for this species in the absence of other lepidopteran species has yet to be established for tomato. In 2005, two methods were field tested for artificially infesting tomato to produce a population of beet armyworm that could cause significant tomato yield loss. In 2006, one of the methods, egg infestation, was used again at higher rates to establish an artificial population of beet armyworm in both early and late season to test for a negative correlation with yield loss. Early infestations were significantly correlated with yield loss, but late infestations were not. An EIL of one beet armyworm per 20 tomato plants was estimated from the 2006 trial based on an early season infestation.