College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ)
Abstract
Powdery mildew on lettuce is caused by the fungus Erysiphe cichoracearum. This disease is favored by moderate to warm temperatures and dry weather conditions. Several potential new fungicides were evaluated for control of powdery mildew on lettuce in 2002. Powdery mildew appeared in our plots by February 15 and reached moderate levels of severity by plant maturity on March 6 to 8th. Nontreated lettuce plants were moderately infected with powdery mildew at plant maturity, whereas the level of disease was low to virtually nonexistent in plots treated with Microthiol Disperss, Rally, Quinoxyfen, Flint, and Rally alternated with Kaligreen. Furthermore, other tested products provided moderate suppression of powdery mildew. The future availability of one or more of the tested chemistries not currently registered for lettuce could help in efforts to control powdery mildew on this crop and to establish and maintain a fungicide resistance management program for plant disease control products
