Five parent strains of T viride and T harzianum and their fungicide resistance mutants were studied for ability to produce of 6-n-pentylo-6H-piran- 2-on (6-PAP) isolated by steam distn. and identified by GC-MS anal. The highest ability for biosynthesis of 6-PAP was observed in the parent strain T. viride F74 (82.6 mg/mL) and its resistant iprodione mutant F74-220 (47.6 mg/mL). The T viride mutants Td50 acquired the ability to constitutional biosynthesis of 6-PAP Only t harzianum parent strain F86 and 2 mutants (F86-272, F86-273) were able to biosynthesize 6-PAP Only T viride strains Td50-40, Td50-57, Td50-127, Td50-B34, Td50-B35 and E harzianum strains F86-272, F86-273 may be used in an integrated plant protection In combination with fungicides.