California’s walnut farmers are on track for a productive season, says Kathy Kelley Anderson, University of California Cooperative Extension pomology farm advisor for Stanislaus County.
That assessment is based on what’s she’s seeing in the county’s orchards and from talking with growers and colleagues throughout the Central Valley.
“There are no major concerns about the crop right now,” she says. “We’ve had a decent amount of nut set, and though it’s still a little too early to tell for sure, I don’t see any real sizing problems. With the way the limbs of Chandlers push out at different times, causing erratic leafing, we’re getting different sizes of nutlets, some of which may not make good size. But overall, the crop looks OK — it won’t be any record breaker, but it should still be a good crop.”
The picture will become much clearer over the next month, she says. By then, any walnut blight and codling moth damage should be apparent.
Also, warming of temperatures to more seasonal levels over the next three or four weeks would help advance development of the crop, which has been delayed by cool temperatures. For example, shell hardening, which normally would have started by the first of June, isn’t expected to begin this year until the end of the month.
In fact, temperatures during the first full week of June had risen some 20 degrees above the 60-degree reading of the previous week. However, any sudden increase of average daytime temperatures into the 100-degree range could burn some leaves and hurt quality by sunburning the nuts.
The cool, wet weather this spring has been similar to last year, Anderson says, when California growers produced their biggest crop ever. Typically, walnut yields tend to decline the year after a high-production season, which seems to be holding true this year.
“We’re seeing some triples this year,” she says. “But, last year we saw a lot of triples — there were just more nuts on the trees in 2010.”
So far, blight hasn’t been the problem that it might easily have been. “Based on the amount of rain this season, it could have caused a disaster in the orchards,” she says. “But, most growers have done a good job of managing it. It could still show up later this season, especially in view of the rains that drenched orchards the first weekend of June.”
Growers with a history of blight problems usually start protecting green tissue from the overwintering bacteria by beginning to apply copper when at least 30 percent to 50 percent of terminal buds have pushed out about an inch. In orchards with low bacteria populations or no previous problems with blight, growers often wait to begin treatment until first flower. As a result, some may spray copper once or twice a season, while others may put the material on as many as six or seven times.
“This year, because of all the rains, most growers have made one or two extra applications,” she says. “That has added to their costs, but the disease hasn’t become rampant and, in most places, it looks like blight is well under control.”
It’s still too early to gauge the extent of the codling moth threat this season. But, Anderson says, traps in many orchards caught more moths than typical in the first of the insect’s three flights this season. As a result, many growers applied their insecticide for the first peak of the first flight.
“If this early treatment didn’t control the moth, we should be seeing some dropping of damaged nuts,” she says. “But I haven’t seen or heard much about that yet. We’ll get a much better idea of codling moth populations in July when we get the second flight.”