Field Trials for Management of Fusarium Wilt of Lettuce

Fusarium wilt of lettuce is severely impacting productivity of the Arizona lettuce industry. The disease, caused by a soil-residing fungus that once established may persist in soils indefinitely, has spread widely throughout Arizona's lettuce growing regions since it was first identified in Arizona in 2001. Romaine cultivars can tolerate the pathogen better than head lettuce, but even with this tolerance, romaine crop losses occur in fields with high disease pressure. Currently, there is no effective treatment to mitigate the disease in lettuce.

To address the increasing concerns of the lettuce industry and the feedback received from stakeholders, The Yuma Center of Excellence for Desert Agriculture (YCEDA) has identified mitigating Fusarium wilt of lettuce as a high-priority issue. YCEDA has managed annual research projects since 2015 to evaluate commercial and pre-commercial lettuce cultivars for resistance to Fusarium wilt, chemical and biological crop protection products for disease suppressing activity, and cultural management via trials in commercial fields. A greater understanding of disease management has been gained from these trials, and this project will continue collecting these important data over the project period by increasing the number of lettuce breeding lines and cultivars evaluated for disease resistance including new commercial cultivars, continuing to evaluate promising crop protection products and evaluating cultural methods for reducing pathogen populations in soil and techniques for avoiding the disease.

Field trials will be conducted in Fall 2020 and 2021 to evaluate commercial seed varieties, pre-release cultivars from university and private breeding programs, and breeding lines from university breeding programs for resistance or tolerance to Fusarium wilt of lettuce, screen wild-type varieties to identify new sources of resistance, and evaluate cultural methods such as transplanting and biosolarization for controlling Fusarium wilt of lettuce. Results will be shared each spring to aid growers in disease management decisions.

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