C A L I F O R N I A
Vegetables A SPECIAL GROWERS’ REPORT OF AG ALERT ®
®
Salinas Valley lettuce farmers and researchers are teaming up to combat impatiens necrotic stunt virus, or INSV, which can leave even surviving plants unfit for market. Current research is focusing on learning where the virus overwinters and which host plants are likeliest to harbor the virus.
Lettuce growers go all out to fight off viral disease ByBob Johnson
ease,” Hasegawa said. “Our strongest area is fromSalinas toGonzales, but we have four sampling sites in the Salinas Valley.” He made his remarks during this year’s California Leafy Greens Board Annual Research Conference as researchers discussed how to contain INSV by identifying and managing important weed hosts, targeting efforts to reduce the western flower thrips that carry the virus to lettuce, and breeding varieties with better resistance to the disease. “INSV is the hot topic right now,” said Leafy Greens Research Board Executive Director Jennifer Clarke. “Growers are really looking for solutions.” The virus has an unusually broad host range that includes many weeds commonly found in the Salinas Valley, and researchers are beginning to document which of these weeds are themost important reservoirs of the disease at different times of the year and in different areas of the Salinas Valley. “The female thrip has to lay her eggs on an infected host,” Hasegawa said. “We need to knowwhich infected hosts the thrips are laying their eggs on. In the winter, we have high populations of weeds hosting this virus.” Plants are ranked by multiplying how frequently they test positive for INSV by the intensity of the pathogens.
The lettuce industry is waging a broad campaign tomanage a persistent viral disease that strikes many Salinas Valley lettuce fields, causing the crop to brown, dry out, and leaving even plants that survive unfit tomarket. Some researchers are looking for genetic resistance to impatiens necrotic stunt virus, or INSV, and others formore targeted control of thewestern flower thrips that transmit the disease. But the key to management could be identifying where the pathogen survives Dec. 7-21, Monterey County’s annual lettuce-free period enacted decades ago to break the cycle of lettuce mosaic virus. “We sampled for INSV during the lettuce-free period to see where the virus is when there is no lettuce in the Salinas Valley,” said Daniel Hasegawa, U.S. Department of Agriculture research entomologist based in Salinas. “We’re starting to build our data base and the top 10 host list changes as we gather more information.” Because many plant varieties can host this virus, researchers took more than 3,200 samples from 42 different weed species at strategic locations over the past 15 months from north of Salinas to as far south as Soledad, to build their list of where the virus lives at different times of the year. “We decided to come up with a list of the most important regional hosts for the dis-
See LETTUCE, Page 8
July 21, 2021 Ag Alert 7
Powered by FlippingBook