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Selection ofconidia/ml). Vegetative growth on culture media and sporulation on culture media, cooked rice and lesser mealworm cadavers were also evaluated. Isolates of B. bassiana were more effective than the M. anisopliae isolates and larvae were more susceptible than adults. The isolates UNIOESTE 04 and UNIOESTE 02 were originally obtained from adults of the lesser mealworm and were the most efficient isolates. In addition, UNIOESTE 04 showed high level of sporulation on different culture media and is considered a potential useful tool to lesser mealworm control.KEY WORDS: Biological control, poultry house, lesser mealworm RESUMO -Este trabalho teve por objetivo selecionar isolados de fungos entomopatogênicos, visando sua utilização no controle do cascudinho, Alphitobius diaperinus (Panzer). Larvas e adultos foram inoculados com suspensões de conídios de 99 isolados de Beauveria bassiana (Bals.) Vuill. e Metarhizium anisopliae (Metsch.) Sorok. em concentrações variáveis de 10 5 a 10 9

The potential of some isolates of Metarhizium anisopliae and Beauveria bassiana for use in the integrated management of Culex quinquefasciatus was evaluated. Metarhizium anisopliae isolate 1037 was selected in initial bioassays with a 50% lethal concentration (LC50) of 1.97 × 104 conidia/ml. This fungus caused higher mosquito larva mortality when applied as a conidial suspension to the surface of the water than as dry conidia, with a time to 50% lethal (LT50) of 1 day compared with 3.6 days for the dry conidial application. However, results with UV‐ and heat‐inactivated conidia did not confirm a possible role of fungal toxins in causing mortality when ingested by C. quinquefasciatus larvae. Metarhizium anisopliae did not remain active for as long as the bacterium Bacillus sphaericus isolate 2362. At 24 h after application, the fungus‐induced mortality on mosquito larvae was significantly lower than the mortality caused by the bacterium. By the second day, almost no activity by the fungus was observed. Results suggest that M. anisopliae isolate 1037 has potential for use in mosquito control programmes.

The mortality of Tuta absoluta (Meyrick) larvae that were fed on leaves of Lycopersicon hirsutum f. glabratum (PI 134417, insect resistant) and Lycopersicon esculentum (cultivar Santa Clara, susceptible) treated with Bacillus thuringiensis var. kurstaki (Btk) was evaluated. Feeding on untreated PI 134417 was detrimental to the survival of T. absoluta larvae. When Btk was applied to the two Lycopersicon plants, mortality occurred in all T. absoluta instars. Application of Btk on tomato leaves had synergistic or additive effects with the resistant genotype on larval survival. This effect was dependent on the instar at which the larvae were fed Btk‐treated leaves. Delayed Btk application may cause higher insect mortality if the insects become more susceptible to the pathogen after a longer period of feeding on the resistant crop.