CALIFORNIA
Vegetables A SPECIAL GROWERS’ REPORT OF AG ALERT ®
In the Salinas Valley, University of California researchers are working to develop plant resistance to new evolutions of longstanding crop diseases in lettuce, including Fusarium, Verticillium and Pythium.
Emerging virus variants are testing lettuce growers By Bob Johnson
Riverside County. “However, its incidence and severity have recently increased in coastal production areas.” Putnam was among other researchers who reported on lettuce disease developments and mitigation efforts during the 2024 California Leafy Greens Research Conference in Pismo Beach and submitted papers on study findings. He said researchers are conducting an updated assessment on emerging Fusarium pathogens in the coastal vegetable region. Identifying the latest strain of Fusarium and finding sources of genetic resistance are essential, he said, because the disease survives in the soil for years, and once it infects a plant, there is little that can be done. According to UC pest management guidelines, the Fusarium pathogen “causes a disease only in lettuce but may be sustained on the roots of many plants.” Once introduced into a field, the fungus will probably remain indefinitely, the guidelines noted.
Central Coast lettuce growers are contending with new variants of destructive crop diseases that have been around for decades but have evolved to complicate efforts to control them. New races of Fusarium and Verticillium make management of the diseases more chal- lenging for vegetable growers, while researchers continue to probe the relationship be- tween various diseases and the mysterious outbreaks of Pythium in many Salinas Valley lettuce fields. One persistent plant disease, Fusarium wilt, is familiar to growers in the Central Valley and warmer areas of Monterey County. Now, a new race of the pathogen, which causes lettuce seedlings to wilt and die, has been found in lettuce fields. “Fusarium wilt of lettuce, caused by the soil inhabiting fungus Fusarium oxysporum, has historically posed a pest challenge in California’s fall-to-spring production regions,” said Alex Putnam, University of California Cooperative Extension plant pathologist based in
See LETTUCE, Page 7
6 Ag Alert June 5, 2024
Powered by FlippingBook