1a.Objectives (from AD-416)
Design, develop, and evaluate area-wide approaches to aflatoxin elimination using atoxigenic strains of A. flavus. Research characteristics required of processes and equipment for production of inoculum by grower run organizations. Produce inoculum and assess commercial compatibility and efficacy of the area-wide approach.
1b.Approach (from AD-416)
In consultation with Arizona growers and gins, an area-wide aflatoxin elimination program based on atoxigenic strain technologies will be designed and tested. Inoculum production will be scaled up and equipment designed and modified to permit production of sufficient inoculum for evaluation of an area-wide program. Requirements for the different stages of inoculum production will be empirically determined. The economics of atoxigenic strain based programs will be assessed and area-wide influences of atoxigenic strain applications will be quantified.
Research activities are carried out both at the Arizona Cotton Research & Protection Council (ACRPC) and at the Agricultural Research Service (ARS) laboratories in Tucson, and these activities are coordinated. In 2009, analyses were performed of short and long-term area-wide influences of multi-year applications of AF36, the biocontrol strain of Aspergillus (A.) flavus which does not produce the potent carcinogen, aflatoxin, to cotton fields in Arizona. The 223 fields included in the test had received from zero to four treatments between 1999-2008. Fields were carefully selected to give a representative sample of different treatment histories. Soil samples from all fields identified in the test were processed and analyzed for levels of the highly toxigenic S strain, the biocontrol agent AF36, and other L strain isolates. There was considerable variation among fields in incidence of the biocontrol strain which was detected in both previously treated and untreated fields. Results are currently being analyzed and interpreted. Follow-up samplings in 2010 in select areas are also being performed. Results are from almost 3,000 isolates obtained through dilution plating. Ninety-five cottonseed samples from the 2008 crop were also analyzed during 2009 to determine if the biocontrol agent AF36 distributed to the crop. Incidences of AF36 on the cottonseed from treated and untreated fields had a wide range of incidence resulting largely from whether the field was treated and the area in which the field was located. During 2009, soil and crop samples were also collected and analyzed for one area that had a long history of extensive AF36 use. This area (Yuma, Arizona) contains a ginning community which has participated for over a decade in development of biocontrol as a partner with the United States Department of Agriculture. More than 100 cottonseed samples were included in these analyses. Pistachio treatments totaling 1,000 acres were initiated in southern Arizona under the Experimental Use Program (EUP) granted by Environmental Protection Agency (EPA) in 2009. This marks the first utilization of AF36 on pistachios in Arizona and is a study that is running parallel with the biocontrol studies in California. Pre-harvest soil and post-harvest crop samples were collected for analysis. Additionally, tests were designed to compare effects of drip versus micro sprinkler irrigation of pistachio on AF36 efficacy. This data is currently being evaluated. AF36 product in the amount of 50,000 pounds was provided to Texas corn growers for testing under direct supervision within an EUP approved by EPA. Based on the results from these studies, the ACRPC has submitted documentation for a full Section 3 labeling of AF36 on corn through IR4 to EPA. Preliminary testing of large-scale manufacture of biocontrol formulations based on sorghum (milo) was initiated in 2009. Equipment will be repaired and modified in 2010 in order to enable continuation and expansion of the development of sorghum based formulations. Research progress was monitored through periodic meetings with investigators in Tucson, Phoenix (at ACRPC) or in fields of cooperating farmers.