A test of economic thresholds for soybeans exposed to stink bugs and defoliation

Abstract

Economic thresholds (ET) for gross tissue removal and piercing-sucking damage by stink bugs are well-established for soybean (Glycine max). However, little is known about the interaction effects of these injuries. During the 2017/18 and 2018/19 crop seasons, field trials were carried out to assess the interaction of defoliation and stink bug (Euschistus heros) infestation and its impact on soybean yield with special respect to oil and protein content and quality. During the 2020/21 crop season, five of the treatments from previous crop season trials were chosen to be repeated. No interaction between defoliation and damage caused by stink bugs was found for any tested parameter. Cages infested with 2 stink bugs m−1 in the vegetative stage exhibited a reduction of yield compared with cages infested with 0 and 1 stink bug m−1, but only during the 2018/19 crop season. Although small alterations in the tested parameters were observed under certain circumstances, overall, the currently recommended ETs for each type of injury proved sufficient. These ETs are: 30% defoliation at the vegetative soybean stage; 15% defoliation at the reproductive soybean stage; density of 2 stink bugs m−1 in soybean fields for grain production; 1 stink bug m−1 in soybean fields for seed production. Those ETs are still valid and can be used by soybean producers separately for defoliation and stink bug infestation.