Submitted to: Extension Reports
Publication Type: Other
Publication Acceptance Date: November 18, 2005
Publication Date: April 1, 2006
Citation: Hua, S.T. 2006. Evaluation of a biopesticide, pichia anomala to control aspergillus flavus for reducing aflatoxin in pistachio. Extension Reports. Interpretive Summary: The Food and Agriculture Organization (FAO) estimates that 25% of the world’s food crops are affected by mycotoxins, of which the most notorious is aflatoxin B1. Contamination of aflatoxin in tree nuts, peanuts, corn and cottonseed has been recognized as a serious food safety hazard to both human and animal. Even very low levels of infection of the crops by A. flavus can result in aflatoxin levels above these mandatory standards of 2-4 ppb. Billions of dollars per year are lost nationally to deal with the problem aflatoxin contamination of agricultural commodities. A visual bioassay has been developed to screen for effective yeasts inhibiting both the growth of the Aspergillus flavus and production of aflatoxin. One particular yeast strain, Pichia anomala strain WRL-076 was selected for further field trial The results of experiments conducted in a commercial orchard in 2005 demonstrated that the biopesticide, P. anomala reduced the frequency of A. flavus colonization by 4 to 10 times as well as decreased total propagules of A. flavus by 75 to 98% in comparison to nut-fruits not sprayed with the yeast.
Technical Abstract: Existing literatures indicate that wounds in plant tissues provide the entry to A. flavus. Two experiments were conducted in a commercial orchard in the summer of 2005. Nut-fruits of pistachio were individually wounded with a dissecting needle. Four treatments were applied. Nut clusters were sprayed with water; sprayed with an aqueous suspension of yeasts at 5x107 cells/ml; sprayed with an aqueous suspension of yeasts at 5x107 cells/ml and two hours later sprayed with spore suspension of A. flavus at 1x103 cells/ml; or sprayed with a spore suspension of A. flavus at 1x103 cells/ml. The biopesticide, P. anomala WRL-076 reduced the frequency of A. flavus colonization by 4 to 10 times and decreased the total propagules of A. flavus by 80 to 99% in comparison to nut-fruits not sprayed with the yeast.