Virus Continued from Page 3
said it is too early to know the impacts of INSV from weedy thrips. “We still have plenty of time left in the season for incidents to get worse in fields,” Grettenberger said. “Warm weather helps generate thrips and build populations among crops and non-crops, creating more vectors moving around in the landscape.” Zischke said growers must also do their part by monitoring weeds on neighbors’ nearby land. “The growers are looking at areas that they don’t have control over in adjacent ar- eas, and they’re working with the ag com- missioner on weed abatement,” she said. “I get calls all the time (about) weeds in an abandoned area or an industrial property. “We’re all pulling together,” she added. “You can’t just think it’s just your neigh- bor’s problem.” Mark Mason of Salinas-based vegetable and strawberry grower Nature’s Reward, agreed this is no time to slow on abatement. “We’re very aggressive on weed abate- ment—hoeing and thinning, keeping the ditches clean, the roadsides,” Mason said. “We’re all in it together.” (Natalie Hanson is a reporter in Alameda County. She may be contacted at natalie. hanson96@gmail.com. Bob Johnson, a reporter in Monterey County, contribut- ed to this report and may be contacted at bjohn11135@gmail.com.)
Wang said. “This is a good start for the rest of the season, because the virus level may continue building up along with the thrips population increasing in the summer.” Wang said part of the reason for success this time around lies with growers’ weed management. Even when a grower con- trols winter weeds in or near their own fields, the virus can find a home in weeds growing in nearby fields and survive. One INSV infestation in 2022 was traced back to weeds on an industrial site as far as 100 yards away. That’s why abatement must continue, es- pecially in known hotspots such as Soledad, Gonzales and Castroville, Wang said. Mary Zischke of the Grower-Shipper Association, who manages the organiza- tion’s INSV Task Force, said she has been keeping a close eye on abatement and oth- er INSV prevention efforts. The task force has been active since fall 2020, during the first of a series of “disas- trous” INSV infections in lettuce crops. A group of growers organized to address impacts of INSV meets biweekly to stay on top of the issue. “During the worst of the epidemic, we were meeting on a weekly basis with grow- ers, the research community, farm advi- sors—whoever might be able to help with the problem,” Zischke said. “It’s a chance
This Salinas Valley lettuce field in late 2022 shows damage from impatiens necrotic spot virus, or INSV. Scientists continue to work on finding lettuce varieties with potential resistance to the disease.
Researchers have identified the 10 top weeds that serve as hosts for INSV and have set up traps throughout the Salinas Valley to monitor populations of thrips. They caution that the disease is usually more severe later in the year, meaning there’s no relaxing for farmers. “Fall is the time when thrips pres- sure and INSV would be the highest,” Clarke said. Ian Grettenberger, a UCCE entomologist,
for growers and pest management to in- terface with scientists and keep that di- alogue going.” Scientists continue to look for ge- netic remedies for the disease. Kelley Richardson, a U.S. Department of Agriculture research geneticist based in Salinas, said two greenhouse trials are un- derway in the hopes of screening lettuce varieties for potential resistance to INSV and another disease, Pythium wilt.
4 Ag Alert June 26, 2024
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