Insect pests and yield potential of vegetable soybean (edamame) produced in Georgia

Abstract

A series of replicated field experiments was conducted with vegetable soybean (edamame), Glycine max (L.) Merrill, to assess the impacts of cultivars, planting dates, and insecticidal controls on insect pest abundance, crop damage and yield potential. The velvetbean caterpillar, Anticarsia gemmatalis Hübner, was the most common lepidopteran defoliator in this study, causing heavy defoliation in some years when left untreated. Other lepidopterans observed included the soybean looper, Pseudoplusia includens (Walker), and the green cloverworm, Hypena scabra (F.). Stink bugs, primarily the southern green stink bug, Nezara viridula (L.), also caused seed damage in some cultivars when left untreated. Stink bug damage exceeded expectations on edamame seeds when exposed to moderate stink bug densities (<3 bugs per 25 sweeps). Other arthropods that were commonly observed included threecornered alfalfa hoppers, Spissistilus festinus (Say), grasshoppers, Melanoplus spp., and the potato leafhopper, Empoasca fabae (Harris). Arthropod infestations on edamame were similar to reported pest problems on conventional soybeans being produced for oil and meal. Midseason applications of the insecticides diflubenzuron plus I-cyhalothrin reduced insect pest populations, percentage of arthropod-induced defoliation and percentage of seeds damaged by stink bugs, but had little effect on edamame yields. Most defoliation and seed damage occurred during R5 development when seeds were approaching full size, thus only minimal yield reductions were noted. However, seed quality of the untreated vegetable soybeans would be unacceptable for the consumer. Total fresh green yields ranged from 2343-11,895 kg ha-1, depending on year, cultivar and planting date, whereas fresh green seed yields ranged from 1208-6,119 kg ha-1. Early-maturing edamame cultivars planted in April had fewer insect pests and less damage than the cultivars planted later. Avoidance of insect pests is an important production consideration for insect management, especially critical in an organic production system. The fresh green seed yields produced during this study demonstrate that this emerging alternative crop has the potential for economic success in the southern region, assuming that the arthropod pests are effectively managed to maintain acceptable edamame quality and yield.