Submitted to: Canadian Journal of Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/8/1996
Publication Date: N/A
Interpretive Summary: There is an urgent need for new sources of natural insecticides because many insects are developing resistance to existing products and environmentally tolerable replacements to these pesticides are becoming fewer in number. A naturally produced fungal product, ochratoxin A, was isolated from survival bodies (sclerotia) of the soil- inhabiting fungus Aspergillus carbonarius. In dietary assays against corn earworm caterpillars, ochratoxin A killed the caterpillars at concentrations 20 times lower than that found in the sclerotia. Ochratoxin A is reported from sclerotia of Aspergillus carbonarius for the first time.
Technical Abstract: Ochratoxin A, a known mycotoxin with demonstrated toxicity to insects, has been isolated from the sclerotia of the fungus Aspergillus carbonarius NRRL 369. The sclerotia, harvested from a solid substrate fermentation of corn kernels at 28 C, produced quantities of ochratoxin A exceeding 50 ppm/g dry wt of sclerotia. Evidence is presented that ochratoxin A accounts for the activity of the methanol extract against larvae of the detritivorous beetle Carpophilus hemipterus (Nitidulidae) (75% reduction in feeding rate) and corn ear worm Helicoverpa zea (50% mortality with 99% reduction in weight gain among surviving larvae) when incorporated into a pinto bean diet at levels less than those occurring naturally in the sclerotia.