Farm Progress

This year’s walnut bloom has been strung out. The straggly bloom may be the result of insufficient chilling hours this past winter.

Greg Northcutt, Contributing Writer

May 23, 2013

5 Min Read

Pushed by warmer than usual temperatures this spring, the crop on Dave Taylor’s San Joaquin County walnut trees were about two weeks ahead of normal in maturity.

His operation, Anderson Barngrover Ranch, near Linden, Calif., includes 320 acres of walnuts.

This year’s bloom has been strung out. For example, by May 14, the nuts on some of his Chandlers had grown to about three-eighths to one-half inch in length. At the same time, other Chandlers had just finished flowering. Taylor suspects the straggly bloom is the result of insufficient chilling hours this past winter.

His Sunlands have set an average number of nuts, while his Vinas and Hartleys have set more nuts than last year. Meanwhile, the nut set on his Tulares is down from 201, and it’s too early to tell for the Chandlers.

Taylor is reserving any crop size estimate until after the June drop. “Some years it can be a very heavy drop,” he says.

The unusually dry weather, which began at the start of this year, continues. The last measurable precipitation in his orchards was .01 inch of rain on April 16. Eight days before that, a quarter-inch of rain fell.

“That was the last of the storms we’ve had this spring,” he says. “We’ve had very little rain this year, and everyone is concerned about it.”

Although light rainfall in March prompted Taylor to make blight sprays, the dry weather has minimized disease pressures in his orchards. At the same time, though, he expects it will drive up his irrigation costs. All his water for his impact sprinkler systems comes from wells.

“Already this season we’re into very frequent and long irrigations,” he says. “With the dry weather likely to continue, I expect my power bills for pumping water will exceed last year’s by quite a bit.”

Because Taylor is planning on an unusually hot summer, too, he’ll be treating his trees with Surround crop protectant to reduce against sunburn. He may even make a second application later in the season.” Some years, like 2011, that hasn’t been necessary, he notes.  Last year, he put on sunblock late in the season and in time to help protect the trees from hot weather shortly before harvest.

He’s ready to respond to any walnut husk fly pressure this season. This tough-to-control pest that damages kernels and stain shells, is becoming an increasingly greater threat in his area.  His Hartleys and Vinas are very susceptible to husk fly damage;

About the size of a housefly, husk flies have one generation a year overwinter as pupae in the soil. They emerge between late June and early September. Maggots hatch from eggs laid below the surface of the husk, where they feed. When mature, the maggots drop to the ground and burrow several inches into the soil to pupate. Most emerge as adults the following summer. But some may remain in the soil for two years or longer.

Moth battle

That erratic emergence adds to the difficulty of controlling this pest, Taylor notes. “We can have a bad infestation one year, nothing the next, and then a horrible one the year after that” he says.

Last year, husk flies emerged late and weren’t around long, he reports. However, he trapped them in new areas.

Monitoring traps closely to determine presence of the adults and precise timing of sprays are critical for controlling husk flies, he adds. Some years, depending on the level of infestation and insecticides used, he may spray his trees every week or two until he stops finding egg-bearing females in his traps or until harvest.

To gauge effectiveness of his control program, he’ll check the windrows during harvest for maggots.

While husk flies may be becoming more of a problem in his area, Taylor has gained the upper hand on the codling moths. At one time, he applied sprays, based on trap counts, to control this pest. He’s replaced that with pheromone emitters for mating disruption. “I can’t say that mating disruption has totally eradicated this pest, but in the last few years I’ve caught very few of them in traps,” he says.

For all of last year, the moth count in his traps totaled just 41, reports Taylor, He notes that some growers, using conventional spray programs, may catch as many as 40 in a single night.

What’s more, in each of the last three harvest, processors have found no codling moth strikes in his crop, Taylor says.

Some years he pays more per season for the pheromone material than he would for an insecticide to control this pest. However, the long term benefits of his mating disruption program outweigh the added short-term expense, Taylor reports.

“I don’t spray for codling moths anymore,” he says. “I no longer have any codling moth damage. And, I end up with three percent to eight percent more walnuts to sell.”

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 DuPont Crop Protection. If you 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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