CALIFORNIA
Vegetables A SPECIAL GROWERS’ REPORT OF AG ALERT ®
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Prior to planting lettuce in this Salinas Valley field, soil is treated with steam. Experiments by University of California researchers show that steam may be as effective as fumigants to control weeds.
UC highlights new technology to battle pests, weeds By Bob Johnson
The figures for production cost in that study were derived from interviews with vegetable growers in Monterey, Santa Cruz and San Benito counties. Steam treating a band of soil along the seed line can rid the planting bed of pathogens and viable weed seeds. Applying a spot treatment to the area where the crop is planted reduces the need for steam by 93%, Fennimore said. “With a 4- to 5-inch band, we’re treating the weeds that are most expensive to remove by hand,” Fennimore said. “Steam reduced hand weeding, improved lettuce vigor compared to Kerb and also helped to control pythium wilt.” In the 2023 trials, the application of a band of steam 4 inches wide and 5 inches deep reduced purslane weeds in the seed line by 99%, shepherd’s purse by 88% and little mallow by 42%. “It’s not knockout, but it’s pretty good,” Fennimore said. “Steam also worked with onions. There were fewer weeds and more large onions than with Dacthal.” UC researchers are studying whether the band-steaming alternative offers some control of fusarium wilt in lettuce. “A French machine makes steam that is 400 degrees Fahrenheit, which disperses better in the soil,” Fennimore said.
California vegetable growers may benefit from new and improved technologies that allow them to manage pests and weeds, while reducing reliance on pesticide applications. Rather than hand weeding, steam treatment of a band of soil along the seed line may be an economical way to manage weeds in lettuce and reduce the need for chemical fu- migation, according to researchers at the University of California Cooperative Extension, who led presentations on integrated pest management at a meeting last month in Salinas. “In vegetable crops, we have a shortage of new registered herbicides. We have to create our own technology,” said Steve Fennimore, a UCCE vegetable weed specialist in Salinas. “We use Kerb, which was registered in 1972, and Dacthal, which was registered when (Dwight D.) Eisenhower was president.” Previous UC experiments have shown steam to be as effective as any fumigant in man- aging weeds or pathogens in vegetables, he said. The problem is treating the entire bed with steam is too slow and expensive to be a viable alternative. “There are engineering solutions to make steam viable for weed control,” said Fennimore, who studies chemical and nonchemical methods of weed control with the objective of reducing costs and to develop automated weeding systems to mitigate labor challenges. Hand weeding iceberg lettuce costs an average of $635 an acre, according to a 2023 UCCE study on the sample costs to produce and harvest film-wrapped iceberg lettuce.
See TECHNOLOGY, Page 7
6 Ag Alert January 3, 2024
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