Larvae of Phthorimaea operculella (Zell.) as affected by various strains of Bacillus thuringiensis

The potential activity of 65 strains of the biopesticide Bacillus thuringiensis was evaluated against the first instar larvae of the potato tuber moth Phthorimaea operculella. The larvae of this insect pest showed to be susceptible to some varieties kurstaki, thuringiensis, tolworthi, galleriae, kenyae and aizawai. Data on the LC 50 and potencies of the highly active varieties (causing larval death of 80% or more) indicate that var. galleriae was the most potent. The LC 50 , for other varieties, ranged between 28.83-101 μg/ml. The different larval instars of P. operculella were affected by B. thuringiensis var. galleriae HD-234 in varying degrees, showing a gradual increase of LC 50 with the increase of larval age.