CALIFORNIA
Vegetables A SPECIAL GROWERS’ REPORT OF AG ALERT ®
Cabbage growers in Ventura County are partnering with researchers at the University of California to control populations of diamondback moths, right. Increased crop damage from diamondback larvae prompted a search for better pest management tools.
Cabbage growers wage war on diamondback moth By Rob McCarthy
according to county crop reports. Concerned about the continuing diamondback moth damage, growers approached Oleg Daugovish, University of California Cooperative Extension vegetable crops advisor in Ventura County. He established a monitoring program using pheromone-baited traps to catch adult males. The traps revealed accelerating levels of diamondback moths. Daugovish said pesticides that area growers had relied on to grow market-ready cabbage and Brussels sprouts were becoming ineffective in treating the moths compared to results in other coastal areas in the state. “It was just a matter of time,” Daugovish said. “The resistance was developed to just about every mode of action that we have.” The diamondback moth is found everywhere cabbage is growing in Ventura County, making it California’s hottest spot to study and collect data. As a result, Daugovish is in- vestigating potential integrated pest management steps that could complement new crop protection materials when they become available in the state. One material not yet registered in California was effective in Arizona trials and will be tested in Ventura County, said UCCE staff entomologist Hamutahl Cohen. The product name is Plinazolin, which has the active ingredient isocycloseram for disrupting the moth’s nervous system.
Despite having wings, a diamondback moth isn’t much of a flier. That hasn’t stopped it from spreading across Ventura County where cabbage is in the ground much of the year. California cabbage growers have dealt with the moth for two centuries, according to published research. However, a resurgence of the destructive pest is affecting farms along the Southern California coast, where cabbage production is highest and is ramping up ahead of the summer. California is the nation’s top producer of cabbage, with Ventura and Santa Barbara counties leading the state. The region is also ground zero for the diamondback, which is attracted to leafy plants in the brassica family. It can be cabbage or Brussels sprouts. A field of broccoli or a Chinese vegetable such as bok choy are welcome hosts. Yellow mustard, a weed that grows along roadways and near the Santa Monica Mountains in Ventura County, offers enough refuge and nutrition for diamondback moths to reproduce and restart the life cycle. Starting in 2021, growers in the Camarillo-Oxnard area began noticing holes chewed in the leaves and flowers of cabbage transplants. Some blocks of cabbage damaged by diamondback moth larvae had to be disked. Cabbage acreage in Ventura County dropped from 3,194 in 2020 to 2,851 in 2021, and the crop value fell from $37 million to $35 million. While cabbage plantings dropped further to 2,642 acres in 2022, rising prices lifted the crop value to $40 million,
See MOTH, Page 7
6 Ag Alert May 15, 2024
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