Unusually cool spring and summer weather has made this an interesting year for walnut growers, says Wes Asai, Pomology Consulting, Turlock, Calif.
“Walnut trees have been very late leafing out and growing,” says Asai, who works mostly with growers in Merced and Stanislaus Counties. “Typically, we get big flushes of growth in May and June. But, this season much of the growth started late and continued well into August. In good growing areas, though, the crop is looking pretty good.”
Nuts have suffered minimal sunburn and heat damage so far this summer, which has helped maintain quality, though nuts appear small for the size of the crop, he notes.
This season’s weather also helped minimize normal disease and pest problems. “Blight wasn’t much of an issue and pest activity has been very low,” Asai says. “Natural parasites have controlled aphids; their numbers have also been very low.”
As usual, he treated some orchards for mites this year, including earlier varieties like Paynes and Vinas, which he also sprayed to control codling moths.
“Because of the weather this spring, we knew it was going to be a different kind of year for codling moths,” he says. “It was hard to zero in on the start of the first flight because the times they emerged were all over the place. That often makes it difficult to time control treatments. Considering the unusual emergence pattern, I’ve been surprised by how few nut strikes we’ve had, the moderate moth catches in our traps, and the low number of dropped nuts. They haven’t been any worse than any other year.”
Many of his growers also have Chandlers and they’ve had few problems with codling moths over the years. He didn’t treat their trees for codling moth, aphids or husk fly this year — only for mites. In fact, he says, he sprays Chandlers for codling moth either infrequently or not all, depending on the season.
“We just haven’t seen much damage from pests this year,” he says. “Whether or not the threat stays like that until the end of harvest remains to be seen, but right now, as we start harvesting the nuts, it doesn’t look like pests will be a problem for us.”