Evaluation of the Entomopathogenic Fungi Beauveria bassiana and Paecilomyces fumosoroseus for Microbial Control of the Silverleaf Whitefly, Bemisia argentifolii

c s t u a 1 b d f a a i 1 b Collaborative research was conducted at the USDARS Subtropical Agricultural Research Center in southrn Texas to assess the microbial control potential of eauveria bassiana and Paecilomyces fumosoroseus gainst Bemisia whiteflies. Laboratory assays demontrated the capacity of both pathogens to infect Bemisia rgentifolii nymphs on excised hibiscus leaves incubated t relative humidities as low as 25% at 23 6 2°C (ca. 35% nfection by B. bassiana and P. fumosoroseus resulted rom applications of 0.6–1.4 3 103 conidia/mm2 of leaf surace). In small-scale field trials using portable air-assist prayers, applications at a high rate of 5 3 1013 conidia in 80 liters water/ha produced conidial densities of ca. –2.5 3 103 conidia/mm2 on the lower surfaces of cucurbit eaves. Multiple applications of one isolate of P. fumosoroeus and four isolates of B. bassiana made at this rate at 4o 5-day intervals provided G90% control of large (thirdnd fourth-instar) nymphs on cucumbers and cantaloupe elons. The same rate applied at 7-day intervals also rovided G90% control in zucchini squash, and a oneourth rate (1.25 3 1013 conidia/ha) applied at 4to 5-day ntervals reduced numbers of large nymphs by G85% n cantaloupe melons. In contrast to the high efficacy f the fungal applications against nymphs, effects gainst adult whiteflies were minimal. The results ndicated that both B. bassiana and P. fumosoroseus ave strong potential for microbial control of nymphal hiteflies infesting cucurbit crops. r 2000 Academic Press