Moisture and soil type are primary drivers of Helicoverpa zea (Lepidoptera: Noctuidae) pupation.

Abstract

Studies in the lab have demonstrated that evaluating the effect of soil moisture and other variables is essential for understanding the importance of environmental factors influencing the Heliothinae pupal stage, but simulated field studies are conducted infrequently. We compared the pupation of Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae) under saturated and unsaturated conditions across 3 distinct soil types (coarse sand, high organic muck, and fine-textured clay) and observed adult emergence, as well as pupal depth and weight. The interaction between soil type and moisture had a significant effect on adult emergence. Fewer adults emerged from dry fine-textured clay soil than from dry coarse sand and high organic muck. However, there was no effect of soil type and no interaction between soil and moisture on pupal depth. Soil moisture was the primary driver of pupal depth, suggesting prepupae use moisture to mediate their position within the pupal chamber. In addition, pupal weight was unrelated to soil type, moisture, or their interaction. Our study demonstrates that soil moisture can be a greater driver of H. zea pupation than soil type, but additional observations are necessary to understand the mechanism by which moisture impacts pupation.