REPELLENCY OF LOCAL DIATOMACEOUS EARTH ON WHEAT AGAINST SOME COLEOPTERAN STORED-PRODUCT PESTS

Abstract

In this study, the repellent effect of a local diatomaceous earth (DE) formulation (Demite (R)) was evaluated on monolayer and bulk wheat against three coleopteran stored-grain pests: the lesser grain borer (Rhyzopertha dominica (Fabricius), Coleoptera: Bostrichidae), the confused flour beetle (Tribolium confusum Jacquelin du Val, Coleoptera: Tenebrionidae), and the rice weevil (Sitophilus oryzae (L.), Coleoptera: Curculionidae) Two-choice tests were conducted to assess insect behavior on treated and untreated surfaces at a DE concentration of 1000 ppm. The experiments measured insect preferences on monolayer wheat surfaces and within bulk wheat at specific observation intervals. The repellency tests were performed under controlled conditions: 25 +/- 1 degrees C temperature, 65 +/- 5% relative humidity, and complete darkness in an insect growth room. The repellency of Demite (R) significantly varied between application methods. On monolayer wheat, the strongest response was observed for T. confusum (97%), followed by S. oryzae (72%) and R. dominica (56%). In contrast, bulk wheat tests showed higher repellency for S. oryzae (90%) and T. confusum (89.3%), while R. dominica exhibited lower responsiveness (53.3%). Significant differences in repellency among the insect species were detected. Sitophilus oryzae and T. confusum exhibited strong repellency across all observation periods, whereas R. dominica was less affected by DE-treated wheat. In conclusion, the local DE formulation demonstrated notable repellent properties, making it a valuable tool in stored grain pest control strategies.