AF36 is a strain of fungus/mold that does not produce toxic aflatoxin, and has been approved by the EPA and California Department of Pesticide Regulation (DPR) to be applied to pistachios statewide, and cotton in the Imperial Valley. Besides California, the safe isolate has been used in corn, peanuts, and corn—-where historically high levels of aflatoxin have limited the sale of commodities to consumers or to animals as feed.
For this season there is enough material to treat at least 60,000 acres—possibly much more due to a drought in Texas, freeing up AF36 that was destined for corn growers.
The pioneering work in pistachios was done by Dr. Themis Michailides, along with Dr. Mark Doster his Staff Research Associate. Both are plant pathologist and work at the Kearney Agricultural Research and Extension Center in Parlier. Michailides worked closely with Dr. Peter Cotty, USDA ARS in Tucson who has spearheaded the work in cotton for Arizona Cotton Research Protection Council (ACRPC). “We cooperated with Dr. Cotty very closely and borrowed his experience and applied it pistachios,” said Michailides. “In cotton, the problem is that toxic aflatoxin infect cotton seed, which restricts it from being used as animal feed.”
The ACRPC is so invested in the AF36 solution that the organization built a manufacturing facility in Phoenix and will be supplying the material throughout the nation.
Aflatoxins are carcinogenic toxins, a metabolic byproduct produced by various strains of a common fungus/mold, Aspergillus flavus (Af). “There is a lot of variability in the fungal population. Some isolates don’t produce any aflatoxin, while some produce a lot,” said Bob Klein, Manager, Administrative Committee for Pistachios.
This has ben a long-term research program starting in 1991 when the USDA began a program called the Alflatoxin Elimination Working Group. Early funding for the AF36 research came from the USDA, with later funding from pistachio grower assessments.
AF36 is a strain of the fungus that does not produce aflatoxin. It was isolated from fields in Arizona and California. “We are enhancing the populations out in the field, which means we are reducing the number of toxigenic strains, explained Klein.
The fungi primarily live on dead organic matter. The strategy is to get into the field with the nontoxic isolates, which will reproduce on the limited organic matter, before the natural isolate populations, that could be toxigenic have a chance to increase, noted Klein. “One of the basic rules of ecology is that whatever gets to that niche first…wins. So, what we are essentially doing is changing the population,” noted Klein.