Robert Van Steenwyk has been studying Walnut Husk Fly for decades, looking at various alternatives to control the pest.
His research laid the groundwork for growers to apply less pesticides than they used to.
Even with all his experience, Van Steenwyk still is surprised by what he sees sometimes, he told growers at the Walnut Trade Show in Yuba City this year.
“Many of the people sitting here have gone way beyond what we imagined, down to 1 gallon per acre,” Van Steenwyk told the crowd. “And they have good control.”
Van Steenwyk said alternating rows in applying insecticide is a variation of the low volume method that’s spread throughout the state.
“What a lot of growers have done is cut the volume and go every other row--so they don’t go low volume, they go intermediate volume, which is still very helpful for control and cost,” he said. “The PCAs recommend that you cut your volume down and you go every other row. They think this is standard now.”
Growers doing low-volume insecticide application for Walnut Husk Fly should use standard coverage if multiple pests are present in the orchard, Van Steenwyk said, calling out codling moth and others.
Despite his success to date, Van Steenwyk isn’t resting on his laurels.
“We’ve done many experiments, various techniques. The last one this last year, was we used pretty low volume and we switched out the bait,” he said in an interview. “We’re trying new baits now to make it more effective.”To sum up? Van Steenwyk’s message for growers regarding insecticide for Walnut Husk Fly is simple:“Low volume was as effective as the grower standard, and there was no significant difference observed,” he said. “If you are not doing it, try it out, you'll like it.”
Additional Information For Growers
Below you can find a table Van Steenwyk shared with the relative effectiveness of different insecticides.
Here are links for further information: