California Walnut Board Focuses On Research
October 17, 2016 It’s no secret walnut growers, like most of their counterparts farming the 300-plus crops that flourish in California, have some large obstacles looming. Soaring land and production costs — coupled with the drought and increasing government regulations — are certainly daunting.
“We’ve got some major challenges ahead, that’s for sure,” says Jerry Moore, who farms walnuts in the southern San Joaquin Valley, just east of Visalia.
Moore, of all growers, should know. He serves as Chairman of the California Walnut Board’s Production Research Committee (PRC). The committee takes recommendations from the Production Research Advisory Council (PRAC), which was formed a decade ago.
PRAC is composed of eight members, including both growers and University of California Cooperative Extension (UCCE) farm advisors, who go over all the research possibilities. They then prioritize them, assigning a rating of 1 to 5, depending on importance.
PRC looks at those ratings and then makes the final decisions. The two groups work hand in hand, says Moore, though the PRC makes the calls on funding.
One change this year is for the first time in two decades, Dave Ramos won’t be directing the research. Moore says PRC will miss Ramos, who retired after 18 years.
That said, Moore says PRC is happy to have Joe Grant on board. After recently retiring after 30 years as a University of California (UC) Cooperative Extension Farm Advisor in San Joaquin County, Grant is taking over the half-time post as Research Director.
“We’re so happy to have Joe,” Moore says. “He will add a lot to what we’re doing in research.”
Grant is perhaps best known in research circles for his work on the biocontrol of codling moth. By instructing growers on the benefits of mating disruption, the industry was able to move away from its reliance on chemical controls. Grant’s efforts earned him and the Entomology Working Group within PRAC the IPM Innovator Award from the California Department of Pesticide Regulation in 2013.
Asked what areas of research were the priority of the PRC in the coming year, Moore listed genetic improvement – both in varieties and rootstocks – orchard management, tree nutrition, and insect control. Grant fleshed out these topics in more detail:
Genetic Improvement
In general, the California Walnut Board supports a mixture of short- and long-term efforts. Short-term efforts take the form of such things as cultural practices and crop protection sprays. Long-term efforts generally include breeding.
Some problems are difficult indeed to solve. Take Walnut Blight, which was first reported about 100 years ago in Southern California, where the industry was founded before moving to the San Joaquin Valley. Growers are still fighting that difficult disease, and mostly with one ingredient, copper.
But now the industry is advancing into walnut genome research. Now that the walnut genome has been mapped, it won’t be too long before researchers use faster breeding methods to develop walnut blight-resistant varieties.
The industry is doing a lot of research to find new disease-resistant rootstocks, such as the RX1 and VX211, two so-called clonal Paradox rootstocks. “We are rapidly getting to a place where we’re going to have more options for more and better characteristics,” he says.
One overriding goal is trying to find an early-harvest ‘Chandler.’ It’s by far the most popular variety in the state, accounting for well over half the production. If there were a variety similar to the late-harvesting ‘Chandler,’ growers could smooth out the harvesting and processing season.
Timing, as well as quality, is the reason for the success of ‘Ivanhoe,’ which was released by the walnut breeding program at UC-Davis headed up by Chuck Leslie a half-dozen years ago. Not only does ‘Ivanhoe’ produce the desirable light-colored kernels for which the popular ‘Chandler’ variety is known, but it is harvested a month before ‘Chandler.’
‘Ivanhoe’ works great for growers like Moore in the south, and lots of ‘Ivanhoe’ acres are being planted. But it leafs out too early for Northern California growers, who get more rain, earlier, and can get blight. Up north, growers are trying ‘Solano,’ which appears promising. But perhaps the most promising variety to come along recently is the just-released ‘Durham,’ which is still something of an unknown but looking good.
Orchard Management
With the pressures that California growers face with cost of land, the cost of inputs, etc., researchers are looking for every possible means of improving profitability. Higher production, sooner, and lower costs are needed. How to get highest possible production as fast as possible? Intensified orchard production is the result.
“That’s translated into greater planting densities, which call for new pruning practices,” Grant says. “In early years we get more production per acre out of dense orchards, but those dense orchards can have problems as trees age because of low- light intensity, high humidity, etc. A lot of research is being done on irrigation optimization efficiency.”
Bruce Lampinen, who earlier this year was endowed with one of the first UCCE chairs, has been looking at a practice that used to be unthinkable: nonpruning of walnuts. It’s all part of the modern production system.
“We’re pretty much expected now to get 3.5 tons per acre by the 7th or 8th leaf, and a couple decades ago that production would have been unheard of,” Grant says. “We’re really intensifying production, but there are limits to this, and that’s part of our research, finding what those limits are.”
While in the old days a grower would plant an orchard and leave it in the ground for 30 to 40 years, that might not meet today’s expected short- and medium-term production goals. Variety and rootstock replacement are other considerations.
“Today a grower might replant after 25 years,” he says. “It’s a different way of looking at it.”
Tree Nutrition
Optimizing fertilizer use, especially of nitrogen (N), is a paramount consideration. According to Grant, the key question is: “Do we need all that we put on, or can we put on less and save money while still getting top production and quality?”
It’s becoming more of an issue today because growers now know how much N a walnut crop uses so the industry now has data to justify what growers are doing. That’s particularly critical now that N leaching into groundwater aquifers has become such a big issue with state regulators.
“But growers want to be efficient, anyway,” he notes. “We’ve got to be responsible using this nutrient, so we’re trying to be as efficient as possible.”
Insect Control
In the past 20 years, the walnut industry has spent a lot of money on controlling codling moth, which has done a lot of damage. However, now growers have a number of answers. Not only with insecticides, but pheromone mating disruption. Today, codling moth is no longer Enemy #No.1.
Now, NOW is.
“In recent years, navel orangeworm (NOW) seems to be fast becoming the major worm pest of walnuts,” Grant says. “Researchers are trying NOW mating disruption, and that shows promise.”
Walnut husk fly is also an emerging and increasing problem, even worse than codling moth. Walnut husk fly is showing up in new orchards where it’s never been seen before. Some suspect that not spraying for codling moth has allowed husk fly to flourish. Or perhaps it’s the move to the newer, denser orchards, which have the higher humidity husk flies favor.
Mites continue to be a problem, recent research has shown most walnut orchards don’t have the beneficial insect populations that were thought to be there. Without predatory mites like the Western Orchard Predatory Mite, damaging mites can thrive. More research is needed to understand all the other predatory mites so the industry can help preserve them and get some beneficial impacts.
Walnut scale is another pest of concern. Its prominence has more to do with the fact that it may be contributing to botryosphaeria, which kills walnut branches. It’s been a major focus of research the last few years.
“We had a wet year in 2010 and all of a sudden the disease was all over the place,” he says. “It’s a major contributor to dieback and decline. Scale feeding seems to predispose walnuts to worse botryosphaeria — that’s the concern.”
The good news is that there are, or soon will be, new materials and approaches that can help with all of these walnut pests. “Our research program has the goal of providing growers with new tools to help them save money, produce a higher-quality product, and be good stewards of their resources,” Grant concludes. ●
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