LARVAE OF PHTHORIMAEA-OPERCULELLA (ZELL) AS AFFECTED BY VARIOUS STRAINS OF BACILLUS-THURINGIENSIS

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