Walnuts Archives - West Coast Nut



NOW in Walnuts

Contiguous acreage of nut crops in California is making navel orangeworm (NOW) a more pressing pest concern for walnut growers, according to Emily Symmes, Sacramento Valley area IPM advisor with the UC Statewide IPM Program and Cooperative Extension. “Navel orangeworm has a broad host range and availability in the state, with tree nuts among the preferred hosts,” Symmes said. “And we are seeing expanded, contiguous acreage in tree nuts of almond, walnut and pistachio, up nearly 50 percent in bearing acreage over the last decade.” The contiguous acreage makes NOW movement and spread a significant threat to nut crops. “What we (researchers) did is we mapped the walnut, almond and pistachio acreage in the state,” Symmes said. “In the Central Valley we see this expanding continuous acreage of nut crops prime for NOW.” She explained this pattern creates a staggered crop phenology, “which means we have this continuing available host...

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Let the Tree Dictate When to Start Irrigating

There are many available techniques for scheduling irrigation in walnuts during the season, says Ken Shackel, Professor in the Department of Plant Sciences at UC Davis. These schedules are based on weather, soil measurements, plant measurements and “WYND - What your neighbor does.” “But, how do you know when to start irrigating,” he asks. The most proposed method of late for scheduling irrigation is Evapo-Transpiration (ET). But newer research suggests there may be better alternatives for determining when to start. He explains that growers worry about two things--starting too late, and starting too early. “Growers worry that if they wait too long, trees will use up the deep soil moisture and run out of their bank account at harvest,” Shackel said. [caption id="attachment_5052" align="aligncenter" width="1024"] A research team has learned to-date that a plant-based irrigation delay strategy appears to be working similarly...

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Organic Walnuts

Quality organically grown walnuts are not produced with neglect but with careful planning and management. Rachel Elkins, UCCE pomology advisor for Lake and Mendocino Counties, where a large percentage of California’s organically grown walnuts are produced, said “growers need to farm their trees”, understand the need for long term planning for successful organic walnut production and to communicate with their certifier. Costs for inputs in organic walnut production, Elkins added, may be higher than in conventional production, but the market has been stable, allowing production to continue. Planting the Chandler variety has been another positive aspect of the organic market in high elevation Lake County Elkins said, due to its lateral bearing, good quality, and late spring leafout, which limits exposure to walnut blight and early season insect pests. Production costs and returns are optimal were pest management inputs are minimized. That is not to say there are no big...

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Walnut Pest Management: Walnut Husk Fly & Pacific Flatheaded Borer

It seems that growers are always battling pests in order to protect their crops. While we looked into navel orangeworm and codling moth in the first part of this two-part series, this second part shines the light on walnut husk fly and the Pacific flatheaded borer. So just how concerned should a walnut grower be about these pests? They don’t require equal interest, as one is more of a concern than the other. Walnut Husk Fly About the size of a housefly, and far more colorful, the walnut husk fly has one generation per year, in which female flies lay eggs beneath the surface of the walnut husk. The first sign of infestation is a point-sized, stinglike mark on the husk. And while it might initially be an easy miss, the husk will eventually show black marks as the eggs hatch and the maggots feed and destroy it. After feeding,...

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Increasing Evidence of Pacific Flatheaded Borer Attack in Walnut Orchards in California

Background and Pest Status Flatheaded borer is a larval stage of one specialized group of beetles (Insect family-Buprestidae), which are glossy iridescent colors. The name ‘flatheaded’ comes from the enlarged and flattened shape just behind the head of the larval stage (Fig. 1) of the beetle (Fig. 2), and the flatheaded borer species that has become a major issue in walnuts is Pacific flatheaded borer (PFB), Chrysobothris mali, which is known to present in the western states such as Washington, Utah, Oregon, California. A similar type of borer species causing serious damage in various nurseries and other fruit and trees in the eastern part of the United States is called Appletree flatheaded borer, Chrysobothris femorata. Although Pacific flatheaded borer has been an occasional pest of young fruit and nut crops in the past, in recent two years, this borer has become a...

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