Efficacy of the entomopathogenic nematode Steinernema riobrave against the stored-product insect pests Tribolium castaneum and Plodia interpunctella

Persistence of stored-product insects in hidden refugia and their subsequent movement into stored commodities resulting in product infestation contributes to their pest status and represents a potential target for biological control agents. Entomopathogenic nematodes have not been previously tested against stored-product insects in environments such as empty grain bins or food processing and warehouse facilities, but their effectiveness at finding and infecting hosts in other cryptic habitats has been demonstrated. In laboratory bioassays, Steinernema riobrave reduced survival of red flour beetle, Tribolium castaneum, larvae, pupae and adults from 77.9 ± 3.2% in the controls to 27.4 ± 2.5% in treatments. Temperature (25 and 30 °C) and relative humidity (43, 56–57, 75, and 100%) did not significantly influence S. riobrave efficacy in this experiment. Field trials simulating empty grain bin treatments were conducted using red flour beetle and the Indian meal moth, Plodia interpunctella. Total survival of mixed stages (larvae, pupae and adults) of T. castaneum was 42% of that in the control and total survival of mixed stages of P. interpunctella was 27% of the control. Larval stages were the most susceptible to S. riobrave for both insect species with P. interpunctella larvae having 99% mortality and T. castaneum larvae having 80% mortality. S. riobrave shows promise as a biological control agent for stored-product insects, particularly Indian meal moth, but further studies looking at combinations of treatments may further enhance efficacy.