Microhabitat Distribution of Velvetbean Caterpillar (Lepidoptera: Noctuidae) Pupae in Soybean Fields in Louisiana

Abstract

The microhabitat distribution of velvetbean caterpillar, Anticarsia gemmatalis Hubner, pupae was studied in soybean field cages and fields during 1985, 1986, and 1987. Larval density did not affect pupal horizontal distribution patterns related to direction and distance from the plant row. Pupae were found equally on both sides of soybean plant rows in a cage study. Pupae were found on and below the soil surface but not on the plant. The majority (84.5%) of pupae were found <2 cm under the soil surface. Soybean with conventional (91 cm) and narrow (51 cm) row spacings had different pupal horizontal distribution patterns. In narrow row spacing, equal numbers and similar dispersion patterns of pupae were found on either side of the plant row. In conventional row spacing, pupal densities varied inversely with distance from the row. Also, pupal densities were slightly biased to the north side (4:6) of the plant rows in 1986, and this trend was extreme (2:8) in 1987 when plant canopy was barely closed. Implications for pupal sampling are discussed.