Efficacy of Selected Insecticides against Eggs of Euschistus servus (Say) and Acrosternum hilare (Say) (Hemiptera: Pentatomidae) and the Egg Parasitoid, Telenomus podisi Ashmead (Hymenoptera: Scelionidae)

Brown (Euschistus servus) and green (Acrosternum hilare) stink bugs are major pests of cotton.  Although various insecticides are commonly used to control nymphs and adults, little is known about how they affect eggs.  Recently published survey results showed high levels of naturally-ocuring parasitization of brown stink bug eggs by the egg parasitoid, Telenomus podisi.  The impact of insecticides on these developing parasitoids has not been assessed.  Laboratory bioassays and field trials were conducted to determine insecticide efficacy against healthy and parasitized stink bug eggs.

Healthy and parasitized egg masses were obtained from lab-reared colonies established from field collections of adults.  Common field rates of acephate, lambda-cyhalothrin, spinosad, and thiamethoxam were tested on healthy brown and green stink bug eggs, as well as eggs parasitized by T. podisi.  In the bioassay, egg masses were dipped into insecticide/water solutions (water as the control) for one second and assessed for mortality after two weeks.  For the field trials, treatments were randomly assigned to field plots using a 4-replicate, randomized complete block design.  Egg masses were pinned to leaves in each plot, and pesticides were applied using standard field application equipment.  Eggs were returned to the laboratory after 24 hours, and mortality was assessed after two weeks.

A. hilare developing in eggs which were dipped experienced 100% mortality when exposed to insecticide treatments; however, when treated in the field, mortality decreased to 50% or less for all treatments.  Lambda-cyhalothrin resulted in significantly more mortality than water.  Both dipped and field-tested parasitoids in brown stink bug eggs showed 100% mortality when exposed to all insecticide treatments.  When dipped in thiamethoxam, developing E. servus embryos had a slightly increased mortality compared to other treatments, but there was no significant difference among treatments in field-tested eggs.