After a sluggish start, walnut trees in the north end of the Sacramento Valley shifted into high gear with the onset of warm weather.
“Because of the cool weather, bud break and bloom were late, and straggled on until about the middle of the April,” say Rick Buchner, University of California Extension Farm Advisor for Tehama County. “With warmer weather, the trees are growing fast and are pretty much moving into full bloom.”
By mid-May growers should have a good idea of the nut set on later varieties, including Chandler, which represent most of the county’s commercial walnuts.
Plentiful rainfall, following a winter when growers irrigated their orchards to replenish soil moisture, have eased any concerns about availability of water for the growing season. Most growers here have a good supply of groundwater, Buchner says.
“We got a little weather scare mid-March when frost damaged almonds and prunes, and another scare the first week of April, but I haven’t seen significant impact on Tehama walnuts,” he says.”
The first flowers on Chandlers in his test plots near Dairyville, Calif., began appearing April 21 and 22, a tad later than usual, Buchner says. “For the most part, the trees I’ve seen in the county look good; yhey’re clean and healthy.”
Buchner sprayed for walnut blight April 18 and again on the 24th. “We haven’t had any sneaker storms this spring,” he says. “We had two significant rains after bud break, and both times we were able to get our blight sprays on ahead of them. It’s been a good year for seeing rains coming and timing our sprays.”
Codling moth is the first insect to get attention in walnut production. Moth populations are monitored using traps and heat accumulation units to predict egg hatch.
“We set the Tehama biofix at April 19 and caught our first female April 23,” Buchner says. “By April 30 we had 104 moths and about 30 percent were females. Based on both male and female trap catches, plus temperature information from the Tehama CIMIS station, egg hatch should have occurred about May 7 in this area.”