PHOSPHINE TOLERANCE AND RESISTANCE IN TROGODERMA-GRANARIUM EVERTS (COLEOPTERA, DERMESTIDAE)

High tolerance of phosphine was observed among larvae of Trogoderma granarium held in crevices for 2-3 months before fumigation at 20 degrees C. Tolerance was related to larval density during rearing as well as larval age. When larvae from a group of populations freshly obtained from different locations in Africa and Asia were prepared in a similar way for fumigation, a wide range of tolerances was observed, indicating the possible presence of phosphine resistance in at least one strain. Individual variation of tolerance within populations was high for larvae, and instead, a resistance test was devised using 48-h eggs. By this technique, one strain from Africa was identified as resistant to phosphine.