Selection of Beauveria bassiana and Metarhizium anisopliae isolates for the control of Blissus antillus (Hemiptera: Lygaeidae)

Chinch bugs of the genus Blissus (Hemiptera: Lygaeidae) are serious pests of maize, wheat, sorghum and various grasses. This study is the first to screen isolates of Beauveria bassiana and Metarhizitan anisopliae against 4(th) instar and adult Blissus antillus aiming to develop a biological control program for this important pasture pest. Ten fungal isolates were initially screened and three isolates were chosen for further investigation. To determine virulence, insects were inoculated by immersion in concentrations of 5 x 10(8) conidia mL(-1). Mortality was evaluated for 10 days. B. bassiana ARSEF 792 was the most virulent isolate to both nymphs and adults, causing 53 and 78% infection, respectively, and values for LT50 of 7.8 and 5.0 days, respectively. Germination studies were carried out to confirm viability and determine speed of germination as a pathogenicity factor. The production of conidia on the cadavers of insects infected with the three selected isolates was determined. The production of conidia on rice media was also evaluated. B. bassiana CG 24 produced the highest number of conidia on insects cadavers (14.9 x 10(7) conidia per insect) and also on rice media (10.6 x 10(9) conidia per g).