The Visalia program opened with Dennis Balint, CEO of the California Walnut Commission, and other staff members talking of how marketing order assessments have helped grow the industry to a point of doubling since 2000 as consumers have come to see the nut as a healthy source of fat.

The presentation looked at activities of both the commission, funded by assessments on growers, and the California Walnut Board, funded by assessments on handlers.

Balint said last year’s crop, projected at 470,000 tons, “finished at 497,000 tons.” He said prices for in-shell nuts in 2011 averaged $1.46 per pound. Recent foreign marketing successes include a U.S.-Korea Free Trade Agreement that is cutting tariffs on walnuts going into that country.

Kurt Hembree, a Fresno County farm adviser for the University of California, said he would like to see increased use of pre-emergent herbicides in walnut orchards, particularly given that some weeds are developing resistance to post-emergents such as glyphosate.

He said newer pre-emergents can be used to control fleabane, jungle rice, horseweed and ryegrass. Hembree also recommended rotating herbicides and using ones with variable modes of control to broaden and lengthen control and avoid development of resistance. He advises using post-emergents only “to clean up ‘escapes’ when they are small.”

Pre-emergents showing promise include Alion, Pindar and Chateau.  

Bruce Lampinen, a UC Davis specialist in walnuts and almonds, talked of light interception and pruning of walnuts. He said there is a potential for about 100 in-shell pounds per acre for each 1 percent of midday light intercepted.

Lampinen said the highest yields come from traditional spacing and minimal pruning. High density plantings, he said, are hard to manage and hedging cuts production.

Pruning can lead to the potential for limb breakage when it stops, Lampinen said. But he warned if there has been heavy pruning and it stops “there can be a disaster; I’ve seen an orchard destroyed that way.”

Allan Fulton, UC soils and water farm adviser in Tehama County, said it is important – particularly for new plantings – to avoid “missing the target” of the root zone and to use tools that include a pressure chamber, Stem Water Potential device, neutron probes, flow meters and rain gauges to assure the tree gets enough – but not too much – water.

Higher frequency and shorter irrigation sets help establish new trees. Placement of irrigation lines close to the root ball is a key, Fulton said.

Robert VanSteenwyk, Extension entomologist with UC Berkeley, said Delegate, Intrepid and Altacor are pesticides effective on different life stages of the codling moth.

He said the walnut husk fly tends to be more of a problem in climates cooler than in the Central Valley. “But last year we had tons of calls from down here,” he said, joking that perhaps “global cooling is going on.”

He said female husk flies fly high and males low, meaning that it is important to “get materials into the top of the tree.” That may mean aerial sprays, he said.