Development of an IPM program for the tropical sod webworm Herpetogramma phaeopteralis Guenée

Herpetogramma phaeopteralis Guenée larvae are destructive pests of warm season turfgrasses in the southeastern U.S., especially on newly established sod, lawns, athletic fields, and golf courses. To facilitate our research, we evaluated several existing lepidopteran artificial diets for their usefulness in rearing H. phaeopteralis. None of the tested diets was suitable because of high mortality and slower developmental time. I sought to describe the relationship between temperature and developmental rate of H. phaeopteralis mathematically for the first time using Linear (common and polynomial) and nonlinear models (Briere-1, Briere-2, and Lactin-2). The Briere-1 model for all immature stages and total development better reflected T₀, T_opt, and T_L values compare to other tested models. Large quantities of insecticides are used on warm season turfgrasses to combat pest infestations. We screened commercially available entomopathogenic nematode products including Steinernema carpocapsae, S. feltiae, Heterorhabditis bacteriophora, H. megidis and H. indica against three different larval sizes of H. phaeopteralis. All of tested entomopathogenic nematode was phatogenic to H. phaeopteralis larvae in the laboratory, but S. carpocapsae caused the highest mortality. The number of infective juvenile stages (IJs) produced per White trap was significantly greater from larvae infected by H. bacteriophora. Our greenhouse studies suggested that larger webworms were more susceptible compared with small and medium size larvae to S. carpocapsae inside turf pots. Our data suggest that commercial formulations of S. carpocapsae can be a good option for H. phaeopteralis biocontrol. We estimated resistance baselines and concentration response of H. phaeopteralis to six different insecticides including clothianidin, chlorantraniliprole, bifenthrin, acephate, spinosad and B. thuringiensis. On the base of LC₅₀ values of age specific (3rd and 4th) instars, the most toxic insecticide was chlorantraniliprole (4.5 ppm) and the least were bifenthrin (282.7 ppm). Our finding suggest that chlorantraniliprole, the newer insecticide, exhibit longer residual control under field condition compared to clothianidin and bifenthrin. The electrophysiological activity of male antennae was significantly affected by different sex pheromone compound candidates. Z11-E13-16AC and Z11-16AC elicited significantly higher response compare to tested compounds. Thus, we hypothesized that Z11-E13-16AC and Z11-16AC are major and minor sex pheromone compounds of this species respectively.