It’s too early to put a number on the size of the Sutter County, Calif., walnut crop, but Janine Hasey, UC Cooperative Extension Farm Advisor for Sutter and Butte counties, says “Right now, it looks like the crop will be a very big one.”

That’s based on what she’s seeing in different areas of Sutter County and in talking with farmers and processors.

“They tell me this could be our biggest crop ever — some varieties, like Serr, Howard and Tehama, are really heavy with nuts. Howard trees tend to be weak-wooded and the very heavy crop is worsening limb breakage this year. Chandlers also look very good, but aren’t quite as heavy as two years ago.”

These conditions are the result, in part, of the walnut-friendly weather growers have enjoyed to this point in the season.

“Walnuts prefer temperatures on the cooler side,” Hasey says, and this season has certainly provided that. The cool spring reduced pistillate flower abortion (PFA) in Serr and other varieties, which can cut yields. The cooler-than-normal temperatures continued into June and July.

“Last month, the weather in the county was pretty mild, with daytime temperatures mostly in the 80s and low 90s, with only a few days over 100 degrees, and the nights were cool, Hasey says. “That kind of weather could mean good nut quality this year because of less sunburn and quality problems related to irrigation stress, either too much or too little water.”

Insects and diseases haven’t posed much of a threat to walnut orchards this year, she says. Spray applications limited blight to far fewer orchards than expected, given the amount of rainfall the county received in the spring.

Trap counts of codling moth have been late and sporadic. “We had our latest biofix ever — not until late April in a lot of orchards,” Hasey says. “Husk fly was a problem for many growers last year, but so far, I haven’t received many calls about it this summer. Husk fly traps should be monitored until hull split.”

Also adding to the potential size of this year’s crop is the number of young orchards coming into production this season. Featuring newer, more lateral-bearing varieties planted on closer spacings, they have the potential to out-yield the older trees, which they replaced, she says.

The 2010 Walnut Objective Measurement Report is scheduled to be released by USDA/NASS Sept. 3.

Normally, Sutter County growers begin shaking their earliest varieties around mid-September, but because of weather-delayed bloom that may be pushed later this season. Hot, dry temperatures further delay harvest, while cooler, moist weather favors hull split. Growers who treat with ethephon to advance harvest date will increase the potential for light kernels, while reducing the risk of problems caused by navel orangeworm and mold from harvest delays, Hasey says.