Nearly 600 participants in a Statewide Pistachio Day gathering in Visalia were recently served up a smorgasbord of advice on topics that ranged from new regulations on food safety and nitrates in ground water, an epidemic year for navel orangeworm in 2012, a new biopesticide to reduce aflatoxins and new cultivars that could hold promise.
“Water coalitions are running interference for you,” said Bob Beede, University of California Cooperative Extension advisor in Kings County. “You need to embrace the coalitions and fill out the paperwork to keep the coalitions helping us.”
Beede was referring to coalitions of growers that have formed to deal with regulations imposed by the Central Valley Regional Water Quality Control Board. He outlined steps growers can take to meet the nutrient needs for pistachios while coming to grips with increased government scrutiny over nitrates in drinking water.
Increased paperwork can be expected in other arenas as well as water regulation, judging from remarks from Bob Klein, manager of the California Pistachio Research Board.
“Document, document, document, document” was Klein’s advice for growers out to develop farm-specific food safety plans that will be called for under the Food Safety Modernization Act.
“If you didn’t write it down, you didn’t do it,” he said.
Klein talked of other challenges to the industry that include less state funding for research and pending retirements in the University of California Cooperative Extension system. Beede himself is among those expected to retire this year.
“Sixty percent of those in Cooperative Extension will retire within a decade,” Klein said.
On a positive note, he introduced a UC farm adviser on nut crops for Fresno and Madera counties, Gurreet Brar, who had been on the job for just a week at the time of the Visalia meeting. In addition, the Pistachio Research Board is providing funding for a plant pathology specialist at the UC Kearney Agricultural Center; partnering with the California Almond Board to pay for funding an integrated pest management advisor at Kearney; and endowing a plant physiologist position at California State University, Fresno.
Klein also talked of AF36, a wheat-based biological control agent that can be applied with a modified ant bait spreader to combat a fungus that can result in aflatoxins that can cause cancer. He said the cost is about $2 per acre.
Themis Michailides, plant pathologist with UC Davis, elaborated on research that he has done on use of AF36. He said that the fungus that causes aflatoxin can be carried by the navel orange worm and there’s a special vulnerability for pistachio nuts that split early.
Achilles heel of aflatoxin
“It’s the Achilles heel of aflatoxin,” Michailides said, adding that early splitting is a problem for 2 percent to 5 percent of the Kerman pistachio crop. He said ways to combat the splitting include applying sufficient irrigation in the spring to avoid tree stress and using the right rootstocks that include UCB-1 that keep early splits low. Avoiding late harvests can cut down on damage from navel orange worm.
AF36 was used on 73,000 acres of pistachio in 2012. It has been approved for use in pistachios in California, Arizona, Texas and New Mexico.
AF36 was developed in Arizona in a collaborative effort between the Arizona Cotton Research and Protection Council and USDA-ARS scientist Dr. Peter Cotty.
Aflatoxins are carcinogenic toxins/by-products produced by various strains of a common fungus (Aspergillus flavus). For more than 30 years, aflatoxins have cost Arizona’s cotton producers annual losses of over $5 million. Cottonseed containing over 20 parts per billion of aflatoxin cannot be fed to dairy cows, and results in $20-$50 per acre loss in revenue.
Aflatoxins also contaminate corn and peanuts, along with several tree crops including almonds, pistachios and figs.
Pioneering research conducted by Cotty and supported by Arizona cotton producers identified certain native strains of Aspergillus flavus which do not produce aflatoxin, occur naturally in the Southwestern deserts but at very low levels.
One of these atoxigenic (non-toxin producing) strains, Aspergillus flavus AF36, has been shown to competitively displace aflatoxin-producing strains when applied to cotton fields. This displacement is associated with reduced aflatoxin levels in Arizona cottonseed.
AF36 was evaluated in commercial fields in Yuma, Ariz., during the period of 1996-1998. The results suggested a high potential for reducing the vulnerability of all crops grown in a treated region to aflatoxin contamination. This provided the opportunity for an area wide aflatoxin management or suppression program.
The Arizona Cotton Research and Protection Council established a working partnership with USDA ARS and Cotty to both manufacture AF36 and advance atoxigenic strain technology.
NOW, mealy bug
Other presentations at the pistachio day included:
• Joel Siegel, with the USDA’s Agriculture Research Service in Parlier, talked of a “blowup year” in 2012 for navel orangeworm despite a record statewide pistachio crop of more than 555 million pounds.
Siegel looked at three years of heavy infestations for the pest: 2001, 2007 and 2012. He said research indicates the number of degree days for those years was high, meaning that warmer weather could be “fuel for the fire” of an infestation.
Moreover, he said, growers who have had no damage in certain years may relax their management efforts. “It’s man’s fallible nature,” he said. He added that the timing of sprays for the pest is critical.
Damage from navel orangeworm was highly variable in the Central Valley, with Tulare County hit significantly more than Fresno County last year.
• Craig Kallsen, UC farm advisor for Kern County, talked of new pistachio cultivars that include Golden Hills, Lost Hills and Kalehghouchi.
The male “Randy” is the preferred pollenizer for both Golden Hills and Lost Hills.
Kallsen gave some advice on pruning those two varieties differently than the common Kerman variety, for example not tipping the trees late. Both of the newer cultivars are harvested 10 days to two weeks earlier than Kerman. Monitoring for pests should also start sooner in those newer varieties, he said.
• David Haviland, UC advisor in Kern County, talked of problem with mealy bug management in pistachios.
He said it is important for growers to distinguish between the Gill’s mealy bug in pistachios, which can damage trees, and the grape mealy bug, which does not. The grape pest, he said, commonly “goes away, bio controls get it.”
Haviland said now is a good time to monitor orchards for the Gill’s mealy bug, which is indicated by cotton candy-like masses on the trunks of trees.
He said the pest causes kernels that are smaller, nuts that don’t split and sooty mold and honeydew.
Pesticides that can have varying degrees of effectiveness in controlling the pests include Centaur, Movento, Assail, Admire and Sevin.
Haviland said it is important to wash equipment and bulk containers to avoid spread of the pest.
• Beede recommended at least annual leaf tissue sampling as a way to get a handle on nutrient use.
He said that the time of greatest demand for nitrogen is when the kernel is filling. “Don’t put on nitrogen too early,” he said. He said limited amounts should be applied during the spring flush in late March to mid-May.
Beede also said the greatest demand for potassium comes during kernel fill.