- The walnut crop in Merced, Stanislaus and San Joaquin counties and the southern end of Sacramento County may be a little lighter than last year, but it is a decent crop.
The walnut crop in the northern San Joaquin Valley area served by PCA/CCA Rod Walker was looking much better at the end of May than the first part of the season when the weather caused a staggered bloom in a number of orchards.
His business, Professional Crop Consulting/Applied Bio Control, Waterford, Calif., works with walnut growers in Merced, Stanislaus and San Joaquin counties and the southern end of Sacramento County.They grow mainly Chandler, Howard, Tulare and Vina varieties.
The push in Tulare’s started the end of March and lasted almost a entire month, he reports. The prolonged bloom could be related to the full winter chilling hours, he notes.
“The crop may be a little lighter than last year, but still looks pretty decent,” Walker says.
His growers vary in their approach to controlling insect pests. “Some growers will tolerate more crop damage than others before treating their orchards,” he says. “When it comes to a control program one size doesn’t fit all”
By the last week of May, Walker was starting to see walnut aphids in the orchards and was expecting the 2A codling moth flight to begin any time. The 1B flight had ended several weeks earlier. Not counting the first few codling moths he caught in early March, in response to some unusually warm weather at the time, codling moth activity this year started early, he notes. Walker determined biofix this year around March 25 in Stanislaus County and a few days later in San Joaquin and Sacramento counties. Usually, it ranges between March 22 and March 30.
About 20 percent of his growers – those with sandier soils as well as those on river bottom land – treat for nematodes. This year nematode numbers are at their usual levels and some growers began suppressing them latter part of May.
Walnut scale is fairly common in his growers’ orchards. This year they are taking steps to control it.
“Many growers haven’t treated for walnut scale over the past several years and the populations have been increasing,” Walker says. “Now, it’s reached the point where growers are tired of losing inside wood on their trees to the insect. The University of California hasn’t set a treatment threshold for walnut scale. So the growers have, in effect, established their own for taking action to control the insect.”
With hot weather in the forecast for the start of June, Walker was preparing to protect trees from sunburn. Some growers will accept a certain amount of sunburn damage on their trees every year and don’t try to prevent it, he reports. Others want to minimize the threat by coating the trees white.
“It’s one of those prevention expenses that doesn’t necessarily pay every year,” Walker says. “There are several good choices out there. We may be evaluating some calcium carbonate foliar products this season as well for their effectiveness in reducing sunburn. The most satisfying applications for sunburn prevention products that we have seen currently have been by helicopter.”
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 Valent USA. 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.