Exploring the Potential of Entomopathogenic Bacteria for Sustainable Management of Sitophilus zeamais in Maize Storage Systems

Abstract

The maize weevil, Sitophilus zeamais, is a devastating primary pest of stored cereal grains, particularly maize, leading to substantial economic losses worldwide. Heavy reliance on chemical fumigants and insecticides for its management has resulted in the development of resistance, negative environmental impacts, and concerns regarding food safety. Consequently, the development of effective, sustainable, and eco-friendly control strategies is imperative. This study aimed to isolate, identify, and evaluate the efficacy of native entomopathogenic bacteria against S. zeamais as a biological control alternative. A total of 100 garden soil samples were collected and screened for the bacteria that can secrete toxic protein using T3 medium and mineral medium (NYSM). The insecticidal activities were carried out by exposing the insects to different concentrations of the proteins. The study revealed the presence of Paenibaeillus mucilergmous strain KN-18 (PM18), Paenibaeillus species strain S-38 (PS38) and Paenibaeillus konkukensis strain SK 3146 (PK3146) as the entomopathogenic bacteria. The study revealed a significant increase in toxic protein secretion by the isolates (P<0.05) at every 24-h interval. Notably, PK3146 consistently secreted the highest amount of toxic proteins across all intervals. Furthermore, the insecticidal activity of the toxic proteins against Sitophilus zeamais demonstrated a significant (P<0.05) increase in mortality rates after 72 h of exposure. The lethal concentration slope (LCSO) calculation revealed that PK3146 exhibited the highest toxicity, followed by PS38 and then PM18. These findings suggest that the entomopathogenic bacteria isolated in this study hold promise for the biological control of Sitophilus zeamais.