Growing NOW problem poses serious pistachio aflatoxin threat

California's 2007 pistachio crop was not only huge in size, but also alarmingly high in aflatoxin levels — almost 30 percent in at least one sampling.

For an industry facing future record-after-record crops, the prospect of a growing aflatoxin problem is not good. Handlers report unwanted high levels in the nuts processed from this crop.

The problem has become so alarming, handlers are now considering penalties for growers who deliver nuts unacceptably high in aflatoxin levels/Navel orangeworm damage and to reward those who avoid the problem with good management practices and deliver a clean crop.

And giving your handler a very clean crop is not that difficult, according to Bob Beede, University of California Cooperative Extension tree nut crop farm advisor for Kings and Tulare counties.

Beede told the recent Western Pistachio Association's U.S. Pistachio Conference in Santa Barbara that a team of UC entomologists have put together a thorough package of knowledge and control strategies to reduce Navel orangeworm populations, and therefore significantly reduce the chances of aflatoxin in California pistachios.

Food safety is hammered hard at just about every crop production and handling meeting these days. It was no different with pistachios which can ill afford a food contamination crisis.

Pistachios remain almost a niche snack food consumers would quickly avoid if they perceived there was a food safety issue.

Consuming high levels of aflatoxin can make people seriously ill. It has also been linked to liver cancer.

“Folks, we have a problem we have to solve collectively. You have to take Navel orangeworm management with extreme seriousness,” Beede told about 400 growers, processors and PCAs at the conference.

Last season's high levels have been blamed on the “perfect storm” of a heavy crop with strung out maturity, a large percentage of early splits and a late harvest.

Beede acknowledged that it may have been ideal for NOW and aflatoxin, but the overwintering NOW population left behind will not go away.

Nor will the growing number of perennial crops that host NOW go away, particularly almonds, another crop seriously impacted by NOW.

Beede insists that a 7-step program will significantly reduce any overwintering or growing NOW problem.

It begins with sanitation; shaking mummies from trees, blowing mummies off berms into middles, and disking them in.

“It may cost $100 to $150 per acre to do the sanitation work,” said Beede. It may pay off by not getting a call from your processor who says he does not want your pistachios because of high NOW damage/aflatoxin levels.

As important as sanitation and beneficial insects are in controlling NOW, those two things together or alone will not control damaging levels of NOW. Control will go beyond those.

Most all generations of NOW in a season overlap, some in as brief a time span as 10 days per generation. However, the first generation does not overlap with the second. It is that initial flush where growers have a shot at cleaning up overwinter populations with a pesticide.

Beede recommends using one of the new soft, non-disruptive insecticides to control worms then. Don't use an organophosphate early because it will take out beneficial parasites early.

“This first generation early treatment would be around the first week to 10 days of May in a normal year,” said Beede.

He also suggested disking middles in June to break pest production cycles; applying soft materials in July if warranted.

“If you wait until August to do something about a NOW infestation, you will not be able to control NOW with pesticides then” he warned.

“And harvest early,” he added. “Don't wait for all the nuts to split. They won't.”

After harvest, Beede said, is another opportunity to break a NOW reproduction cycle. “Remember when you are harvesting nuts, Navel orangeworm also are harvesting nuts.”

“Look at a post harvest treatment with Intrepid and a pyrethroid,” he suggested.

Early splits create an ideal environment for NOW generations to enter the nut and reproduce rapidly. Early splits last year were correlated to deficit irrigation in many cases, according to one handler.

Emerging NOWs do not have to be high numbers initially to create problems. Beede said one entomologist collected 200,000 mummies, but only 190 adults emerged.

“Not a problem? Let's say there are only two Navel orangeworms per tree in an orchard. Each one can lay 100 eggs giving you 200 eggs per tree. Assuming 50 percent mortality in those eggs, that still leaves 100 worms per tree. That is a problem,” Beede said.

In the pistachio industry, we are all in the same boat when it comes to NOW and aflatoxin … all in the same boat without a commander,” Beede said, indicating that NOW control is a grower-by-grower decision.

However, there is one common thread among growers and it is that there is plenty of information about this insect pest and how to control it.

“One thing we all have is knowledge and knowledge is power,” Beede emphasized.

He encouraged growers to “seize the opportunity” to control NOW and reduce any aflatoxin threat and “preserve the food safety and preserve the market that California pistachios have always been recognized for.”

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