1st Place: Monitoring pyrethroid susceptibility in rice stink bug

Across the Mississippi Delta and the Mid-South, rice stink bug (Oebalus pugnax) is a major late season pest in rice (Oryza sativa L.). Rice stink bug has the potential to cause direct yield loss due to kernel development being restricted, as well as profit loss resulting from discolored kernels receiving a lower grade when the rice is sold. There are currently five insecticides labeled in Mississippi for control of rice stink bug, dinotefuran (Tenchu), gamma-cyhalothrin (Declare), lambda-cyhalothrin (Warrior II), malathion (Malathion 57 EC, Malathion 5EC), and zeta-cypermethrin (Mustang Maxx). Lambda-cyhalothrin is currently the most cost-effective insecticide available for rice stink bug control, but overreliance may lead to resistance issues. In 2021 and 2022, laboratory bioassay experiments were conducted at the Delta Research and Extension Center in Stoneville, MS. The study consisted of liquid scintillation vials, each treated with technical grade lambda-cyhalothrin at various concentrations. Rice stink bugs were collected throughout the Mississippi Delta and one rice stink bug was placed in each vial. Mortality ratings were taken 24 hours after infestation. Percent mortality data suggests that some populations of rice stink bug exhibit increased tolerance to lambda-cyhalothrin at previously lethal doses.  With an already limited number of chemical options for rice stink bug control, the loss of an economical insecticide may be challenging for Mississippi rice producers to protect yields.