Persistence of Bacillus thuringiensisδ‐endotoxin and β‐exotoxin on stored grains and their potency against Plodia interpunctella and Sitotroga cerealella

Abstract: The persistence of B. thuringiensis, δ‐endotoxin and β‐exotoxin was determined. The decrease in activity was slow over a period of 150 days. The reduction in larval mortality of Indian meal moth, Plodia interpunctella was more obvious with the increase of storage period and also with the decrease of the concentration of δ‐endotoxin. The decay in activity, in the case of β‐exotoxin, was more obvious at lower concentrations than at higher concentrations as the time of storage increased. Data showed that the potency of the δ‐endotoxin decreased 15 days after application at 27 and 35°C against both tested species, but with a lower degree in the case of Indian meal moth. On the other hand, the β‐exotoxin showed a rapid decay 15 days after application on both stored wheat and crushed corn against both tested insect species.