Chemigation to manage stink bugs in cotton

This project was designed to investigate the efficacy of injecting insecticides through an irrigation system for managing stink bugs in cotton. Successful demonstration of this concept would enable growers to reduce application costs, minimize applicator exposure and treat multiple fields simultaneously. Insecticides are typically diluted in only 5 to 10 gallons of water per acre when applied by ground rig; however, an overhead irrigation system delivers a minimum of 2715 gallons of water per acre. Laboratory and field experiments were conducted to evaluate the efficacy of dicrotophos or bifenthrin with and without an adjuvant (vegetable oil plus a stabilizing agent) and water. The laboratory generated results show that all three species of stink bugs, Nezara viridula, Euschistus servus and Halyomorpha halys, were killed when exposed to dicrotophos or bifenthrin at ground rig dilution rates. However, less than half of the stink bugs were knocked down when exposed to dicrotophos at chemigation dilutions. All stink bugs exposed to bifenthrin without adjuvant at chemigation dilutions were knocked down, but several E. servus recovered.  When exposed to bifenthrin with adjuvant at chemigation dilutions, several H. halyomorpha and E. servus individuals were not knocked down and even more recovered. In field plots, we observed that application of dicrotophos by ground rig consistently provided maximum suppression of stink bug damaged bolls. Interestingly, the addition of the adjuvant decreased stink bug damaged bolls compared to chemigation with the insecticides alone. These results suggest chemigation research must be validated in the field.