The recent rains in the desert southwest have provided environmental conditions highly favorable for downy mildew on susceptible crops. The duration of nights and mornings with high relative humidity following this rainfall event plus any additional rainfall that may occur in the future will determine the total time that crops will be at risk. Data from a trial conducted on lettuce last year at the Yuma Agricultural Center demonstrated that disease severity could be reduced from 70 to 82%, compared to untreated plants, with treatment programs containing Acrobat, Aliette, Manex, Presidio, Previcur Flex, Prophyt, and Revus. For resistance management, using compounds with different FRAC numbers within treatment programs is essential. The complete report detailing the results from this trial can be obtained by emailing Dr. Mike Matheron at: (matheron@ag.arizona.edu).

For questions or comments on any of the topics please contact Marco Pena at the Yuma Agricultural Center.
College of Agriculture, The University of Arizona, Tucson, AZ.