EFFECT OF SOME PHYTOPATHOGENIC FUNGI AND THEIR METABOLITES ON GROWTH OF HELIOTHIS-VIRESCENS (F) AND ITS HOST PLANTS

Eleven fungal isolates and their secondary metabolites incorporated into artificial diet were tested for oral toxicity to the tobacco budworm (TBW) by examining larval weight, efficiency of conversion of ingested food to body tissue (ECI), pupal weight, days to pupation, and mortality. Two isolates of Alternaria alternata, two isolates of Fusarium moniliforme, three isolates of F. oxysporum and an isolated of F. solani reduced larval weight 90-99% after 7 days and inhibited pupation. ECI was reduced 34-96% in control groups. One isolate of A. alternata reduced pupal weight by 67% and increased the time to pupation three-fold. One isolate of Cladosporium cladosporioides reduced larval weights by 56% and pupal weights by 7%. In a preference test of these isolates incorporated at a 1:4 ratio into artificial diet, 48% of the larvae were found on diet cubes containing autoclaved rice, 19% on standard diet, 10% on C. cladosporioides, 6-9% on F. solani, 8% on A. alternata and 3% on F. moniliforme. The fusarial toxins, T-2 and diacetoxyscirpenol (DAS), were the most active compounds against TBW larvae among the 10 microbial toxins tested. T-2 toxin reduced larval weight by 87%, reduced ECI by 62%, reduced pupal weight by 33% and delayed pupation by 1 week. DAS caused similar but less severe effects than T-2 toxin. AAL-toxin inhibited larval growth and reduced pupal weights by 20% and 13%, respectively. A. alternata, F. moniliforme and F. solani were also phytotoxic to alfalfa (Medicago sativa), crimson clover (Trifolium incarnatum) and wild geranium (Geranium dissectum), which are early season plant hosts of TBW