Factors affecting conidial production of Beauveria bassiana from fungus-killed cadavers of Rhodnius prolixus

The epizootic potential of Beauveria bassiana for control of the triatomine vectors of Chagas' disease was investigated by studying the effects of both biotic and abiotic factors on the recycling of a highly virulent fungal isolate from fungus-killed cadavers of Rhodnius prolixus. The conidial production of B. bassiana from mummified cadavers of R. prolixus required high REI levels of at least 96.5% RH. At 97% RH and 25 degrees C, the amount of conidia per insect ranged from 5.3 x 10(6) (on first-instar larval cadavers) to 1.7 x 10(8) (on adult cadavers) depending on the size of the different stages of development of the host. Under optimal conditions, B. bassiana sporulation from R. prolixus cadavers took place in 4 to 5 days after death. At a high humidity level (97% RH) the intensity of the conidial production from Rhodnius cadavers was little affected by temperature over a range from 15 to 25 degrees C, but it declined at 28-30 degrees C and was null at 35 degrees C. There was only a weak influence of the blood meal of nymphs and its timing on the conidial production from B. bassiana-killed cadavers. The recycling capacity of different B. bassiana isolates, selected for their pathogenic activity to R. prolixus, did not differ. From a vector control standpoint, high humidity appears to be the most crucial climatic constraint. The recycling ability of B. bassiana on fungus-killed R, prolixus might contribute to the regulation of triatomine vectors only after applications during the rainy seasons. (C) 1998 Academic Press.