Soybean Looper (Lepidoptera: Noctuidae) Oviposition Preference Relative to Plant Development in Soybean and Cotton

Abstract

Oviposition choice by soybean looper, Pseudoplusia includens (Walker), of soybean and cotton in two phenological stages was tested in field cages to determine relative oviposition preference for these two crops in a situation similar to early- to mid-season cropping conditions in Mississippi. Moths were released into field cages enclosing four contiguous rows for each of two treatments, and egg density per m of row was determined after the second night. Test 1 paired blooming cotton (planted 25 May) with either blooming (23 June) or vegetative (11 July) soybean. Relative to blooming cotton with 81.1% canopy closure, blooming soybean with 78% canopy closure received 2.6-fold greater oviposition, while vegetative soybean with 41% canopy closure received only 0.24-times the eggs as blooming cotton. Test 2 compared oviposition on the two soybean classes in the absence of cotton. Here, 11.2-fold more eggs were oviposited on blooming soybean than on vegetative soybean. Test 3 paired blooming soybean with either blooming or pre-bloom cotton (planted 23 June). Relative to soybean, the pre-bloom cotton with 68.7% canopy closure received 1.6-fold more eggs than blooming cotton, although neither cotton treatment received as many eggs as blooming soybean. This study suggests that the importance of cotton as a host of soybean looper declines as the crop growing season advances.