Pistachio growers fend off formidable insect foes

Pistachio growers fend off formidable insect foes

The southern San Joaquin Valley is on track to produce another sizable, high quality pistachio crop.

Success by most pistachio growers in dealing with unusually high leaffooted plant bug and navel orangeworm pressure in the southern San Joaquin Valley this season has put the industry on track to producing another sizable, high quality crop.

In-shell weight could total 550 million pounds or more, estimates Bob Beede, University of California Cooperative Extension farm advisor for Kings County. That is, if growers, particularly those on the West Side where much of the state’s crop is grown, are able to find and pay for the water their trees will need to achieve that full production potential.

Last year’s record-breaking crop came in at 555 million pounds.

In mid-April, a number of growers were caught off guard by unexpectedly high numbers of leaffooted plant bugs that survived the winter. Many had anticipated that the dry winter would increase their populations. Others assumed no immediate threat when they first started seeing light damage in their orchards around the third week of April. Consequently, the decision to treat was delayed seven to 10 days before the sprayers were brought in. Leaffooted bug feeding turned out to be so heavy that two insecticide treatments were required to suppress it. “In the meantime, some growers suffered enough nut loss that they wished they’d started spraying earlier,” Beede says. “But, of course, hindsight is always 20-20.”

As entomologists predicted, navel orangeworm pressure has been much higher than usual this season, he notes. “If growers don’t carefully monitor NOW populations and time their sprays based on the recommended accumulated degree-days, the navel orangeworm damage at harvest could be similar to that of 2007,” Beede says.

The same dry weather that fueled this year’s insect pressure has also helped minimize the incidence of disease in California’s pistachio orchards this season.

But, the record dry January and February in much of the state and snowpack that had just 17 percent of normal water content in early May has forced irrigation districts to cut deliveries of surface. The situation is particularly serious for pistachio growers on the West Side of the San Joaquin Valley. They depend largely on deliveries of surface water from the Central Valley Project for their irrigation needs. These growers are scheduled to receive no more than 20 percent of their CVP contract water this season.

“Many growers there are scratching to find the water they’ll need to meet the demands of kernel fill this year,” Beede says. “Even if they can find it to buy, these growers could easily be paying $500 per acre-foot for that water, plus the cost of delivering it to their orchards.”

Kernel fill is expected to begin in mid-June and continue through August. During that period, pistachio trees require full ET to produce maximum kernel size and shell splitting. A shortage of water during this time would cost growers in split nut production this year.

Kernel fill is also the period of maximum nitrogen and potassium use by the trees. “Growers need to make sure they provide their trees adequate levels of these two key nutrients during stage III of nut development,” Beede says.

Early sprays

Beede continues to stress the importance of early-season foliar sprays of zinc, boron and copper for second and third year pistachio trees. “That’s a critical time for these trees”, he explains. ”They need these nutrients to support rapidly developing canopies, especially with the leaf loss associated with shoot pinching for training purposes. At the same time, their relatively small root systems make it difficult to take up these essential elements.”

“Depending on location of the orchard and soil chemistry, once these young trees have about 8 to 10 inches of shoot growth, they need two or even three foliar sprays spaced 14 days apart,” Beede says.

It’s a message he and other farm advisors and specialists have been delivering to growers for at least the past two decades. “Still, today, one of the most common farm calls I make concerns nutrient deficiencies in second leaf pistachio orchards. Growers who continue to doubt the need of these trees for foliar sprays early in the season must be living either in denial or in a cave!”

This report is from Tree Nut Farm Press, a twice-monthly electronic newsletter published by Western Farm Press during the growing season. This edition was sponsored by DuPont Crop Protection.  If would like to receive Tree Nut Farm Press go to the Western Farm Press home page (westernfarmpress.com) and sign up for it and other Farm Press electronic newsletters.


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