San Joaquin County grower begins blight sprays

San Joaquin County grower begins blight sprays

San Joaquin County walnut grower Chris Locke started seeing catkins in Serrs the last week of March. However, he started working on this year’s crop last fall when he planted his cover crop.

As walnut catkins continued to push, California’s growers are applying their first sprays of copper materials to protect trees from walnut blight. Among them was San Joaquin County grower Chris Locke, Locke Ranch, Inc., Lockeford, Calif.

His 580 acres of walnuts include Serr, his earliest variety, along with Vina, Hartley, Howard, Tulare and Chandler, the last to bloom.

Locke started seeing catkins in the Serrs the last week of March. That’s also when his orchards received a little rain. Rain spreads the blight bacteria, which overwinter primarily in dormant buds and pose the greatest threat to early-leafing varieties. However, Locke doubts the small amount of rain at the end of March will cause much of a problem controlling the disease.

“It’s too early to say how bad blight could be this year,” he says.

Locke works an application of Retain in among his blight sprays for Serrs to reduce pistillate flower abortion, which affects this particular variety.


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Also, this month, Locke will tend to the nutrient needs of his trees. He gets help from the cover crop he starts planting the day after he finishes harvesting his walnuts in October. This mix of annuals, which he seeds with a no-till drill, includes nitrogen-fixing legumes, such as bell bean and vetch, plus triticale and mustard.

The large tap root of the mustard and extensive root system of the triticale open up the soil for better water penetration, he notes.

“Our orchards are next to the Mokelumne River,” he says. “So, the soils are pretty well drained. These cover crops just further help.”

The benefits don’t stop there, though. By improving drainage, the cover crops also allow harvesting equipment to get back into the fields sooner following rains

Locke has used cover crops since mid-1980s. He has found that the cover stimulates more microbial life in the soils by increasing organic matter. Organic matter has had risen to the range of 2.5 percent to 3 percent. His goal is to boost that by another point or so.

His cover crops also help buffer the soils. “Because of the location next to the river, our soils could acidify, if we not careful,” `Locke says. “The organic matter helps keep the pH where it should be.”

This report is from Tree Nut Farm Press, a twice-monthly electronic newsletter published by Western Farm Press during the growing season. This edition was sponsored by Valent USA.  If would like to receive Tree Nut Farm Press go to the Western Farm Press home page ( and sign up for it and other Farm Press electronic newsletters.

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