Having made it through a hard freeze during early bloom and a late spring heat wave, the walnut crop in Lake and Mendocino counties reached the mid-point of July in surprisingly good shape.
“In general, it looks pretty darn good, considering what the crop has gone through so far,” says Rachel Elkins, University of California Cooperative Extension farm advisor for the two counties. “Based on number, quality and growth of the nuts, the crop is better than many growers expected it would be at this point. It’s not huge, but there’s a crop there, and it looks pretty nice.”
Unusually windy weather in early April raised concerns about possible reduced pollination. Then, on the morning of April 16, temperatures dropping to the low 20s, killing the earliest flowers in some blocks, and set back newly planted trees, she reports. The colder areas of Upper Lake and Scotts Valley areas were the hardest hit. However, an earlier-than-usual start to the season has enabled later-emerging nuts to mature where damage was not too severe.
This year’s North Coast crop has already experienced several periods of unseasonably hot weather. The most damaging heat occurred during early June, when temperatures peaked above 100 degrees for several days. “The nuts had reached a good size by then, well over 1 inch in diameter,” Elkins says. “There was a lot of surface area and some of the exposed nuts sustained sunburn damage. There is no walnut blight to speak of.”
Although codling moth is a continuing threat to pear growers, it has never been a problem in the walnut orchards of Lake and Mendocino counties, she notes.
One reason may be the late-maturing varieties of walnuts grown here — mainly Franquette, Hartley and Chandler, which are less susceptible to this pest.
“The last codling moth flight coincides with the pear harvest in August,” Elkins explains. “The flight can extend into early September. But, even then, if a pear orchard is nearby, codling moth doesn’t attack our later walnut varieties. The earlier varieties, for example Tehama, have long been removed.”
Navel orangeworm is seldom a problem for walnut growers in this part of the state and, usually, mites don’t exert a lot of pressure, she says. Walnut aphid and soft scale are also sporadic.
Fall webworm, a cyclical pest, is beginning to show up in some walnut orchards. While its numbers can build up significantly, this pest is more unsightly than damaging to a walnut crop, Elkins adds.
The main insect threat to the area’s walnut crop, husk fly, began appearing in the third week of June, about two weeks earlier than usual. So far, she’s heard of no damage. Often the biggest flights of the season take place in late August and early September. Many of the area’s newer growers are still gaining experience in how best to deal with the husk fly, Elkins notes.
With little insect pressure and no reports of walnut blight problems, the quality of this year’s crop is holding up well. “We still have to get through the husk fly season,” she says. “But, for now, the nuts are clean.”
This year’s dry weather continues to raise concerns, Elkins notes. In Mendocino County, the National Weather Service report for the weather station at Ukiah showed a total of 28 inches for the rainfall year that ended June 30. That’s almost 11 inches below normal for that period. Meanwhile, for that same time frame, Kelseyville, in Lake County, received only about 20 inches, about 10 inches below the norm.
“The rain we’ve had came early, too,” Elkins says. “We’ve had little rain since Jan. 1.”
Some intermittent rain in early spring, which provided the equivalent of about one irrigation, enabled irrigated growers to wait before starting to run water until early June, when they usually begin irrigating, Elkins reports. In fact, a pressure bomb reading in one walnut orchard in mid-May indicated fully watered status.
However, continued dry weather may hurt crop prospects for next year, she adds. “The dryland trees are the ones that would really suffer then,” Elkins says. “They need the winter rain.”
This report is from Tree Nut Farm Press, a twice-monthly electronic newsletter published by Western Farm Press during the growing season. If you would like to receive Tree Nut Farm Press, see here for sign-up.