The 2011 pistachio season wasn’t a good one for Arizona grower Steve Seplak. It was an off-year for his alternate-bearing trees, and he expected yields to decline from the previous year — just not as far as they did. They dropped to a disappointing 1,000 pounds per acre.
“In 2010 we had a bumper crop,” he says. “The trees put all their energy into producing nuts, and that left little for growth last year.”
This season, because of the number of nuts forming, he’s expecting much better from his orchard. “I’m thinking of typical on-year yields, somewhere between 3,000 to 3,500 pounds per acre,” he says.
Seplak, a member of the American Pistachio Growers director and president of the Arizona Pistachio Association, owns SAS-Z Nuts. His Willcox, Ariz., orchards include about 20 acres of pistachio trees plus apples, apricots, nectarines, pears, peaches, and plums.
“Right now, the pistachio trees are about a month ahead of normal,” he says. “It’s hard to tell for sure until the kernels start forming.”
Normally, his orchards receive about 2 to 2½ inches of rain over the winter, but Seplak hasn’t seen rain since last October.
There was some frost, though, in early April when temperatures fell to 25 degrees, remaining there for about four hours. “We lost production on the outer edges of the orchards where the wind machines couldn’t reach,” he says.
This year, kernels started the month-long hardening process in mid-June. “The nuts are looking really good,” Seplak says. “So far, we haven’t had much insect activity. Usually by the end of June stink bugs have started coming into the orchard from the hay fields. But, thus far I haven’t seen any damage on the nuts — maybe the weather has been too dry and the bugs haven’t hatched out yet.”
Weeds haven’t been a problem, either. To control heavy infestations, he applies a preemergent herbicide in the winter.
Tumbleweed is his main concern, but with little of it in his orchard this year, he’s only had to spot treat with glyphosate.
Following 18 months of severe drought, prospects for some relief this summer, in the form of monsoon rains, are looking up. Arizona, as well as New Mexico, are on the northern edge of the North American monsoon region, which is centered in northwestern Mexico.
In most years, this period of rainy weather lasts from July through September. Last year, however, the monsoon season brought little rain to Seplak and other Arizona growers. Now, forecasters are calling for this year’s monsoon to be more vigorous than average.
While Seplak would welcome rain, it would also increase the threat of septoria leaf spot, a fungal disease that can lead to premature defoliation. It can spring up in warm weather when moisture remains on the leaf surfaces; the spores germinate and the fungus grows into leaf tissues.
To control septoria, he treats trees with copper hydroxide (Kocide), usually making his first application in early July.
“I put it on ahead of the summer rains, and then I watch the rain gauge,” he says. “When it gets close to 2 inches of rainfall, I’ll give the trees another coating and continue making one application for every 2 inches of rain.”