<I>Beauveria bassiana</I> Infection Alters Colony Development and Defensive Secretions of the Beetles <I>Tribolium castaneum</I> and <I>Ulomoides dermestoides</I> (Coleoptera: Tenebrionidae)

We studied the effect of the entomopathogenic fungus Beauveria bassiana strain GHA on a) colony development of the beetles Tribolium castaneum (Herbst) and Ulomoides dermestoides (Fairmaire) (Coleoptera: Tenebrionidae) under laboratory conditions; and 2) the volatile blend released by both beetles, containing defensive pheromones, by using the solid phase microextraction technique. Colony development of both species was strongly altered 3 mo after treatment with B. bassiana, showing a significant reduction in progeny of 37.5% for T. castaneum and 50.0% for U. dermestoides. We also showed that the volatiles released by T. castaneum diminished close to 20% compared with those of healthy beetles, whereas in U. dermestoides secretions dramatically dropped to 5%, 7 d after immersion in 1 x 10(9) conidia per ml. These results suggest that after infection events take place, fungus-induced diminished secretion of the defensive pheromones may be a physiologic clue for behavioral changes in infected beetles.