Overwintering and spring migration in the bollworm Helicoverpa armigera (Lepidoptera: Noctuidae) in Israel

To clarify the relationship between overwintering and spring migration in the bollworm Helicoverpa armigera (Hübner) in Israel, we caged larvae under field conditions in fall and used sex pheromone traps to monitor field populations the following spring. No diapause was detected in October-exposed individuals. Overall, 67.7 and 89.2% of the individuals exposed to field conditions during November and December, respectively entered pupal diapause. Most nondiapausing individuals enclosed early in the following January. In contrast, postdiapause adults started to enclose synchronously in late April. Approximately 50% of the postdiapaused females enclosed before 6 May, 9 d before 50% of the males did. Capture of field H. armigera moths in sex pheromone traps occurred 1 mo before the eclosion of adults from caged overwintering diapause pupae. Moths trapped before the eclosion of diapausing individuals had lower wing loading, fewer wing scales, and larger relative thorax size (ratio of thorax to head widths). These morphometric data imply that the early season field moths were trapped after long distance flight. Taken together, the phenological and morphometrical data support the notion that H. armigera exhibits an early-spring migratory behavior in Israel. These results are discussed within the context of physiological and genetic data from related studies.