Summer Preplant Soil Flooding To Manage Sclerotinia Lettuce Drop: The Rest of The Story (August 5, 2015)

As stated in my last article, research studies demonstrated that a 3-week period of field flooding during the hot summer months of July and August was an effective cultural means of destroying virtually all sclerotia of Sclerotinia minor and S. sclerotiorum in a field, thus controlling Sclerotinia lettuce drop in future lettuce plantings. This procedure has been used in many fields in the Yuma Valley to manage Sclerotinia lettuce drop. However, a couple of negative effects of this practice have been expressed. One concern is elevation of the ground water table as a result of this soil flooding procedure, particularly in areas already affected by high ground water. Also, in certain areas in the Yuma Valley, damage to the open drainage system has occurred as a result of erosion of the sides of earthen drains. These concerns have led to the initiation of additional field research at the Yuma Agricultural Center to examine and possibly refine the method of water delivery and the duration of soil wetness required to destroy sclerotia of the Sclerotinia drop pathogens. The goal of this research is to achieve destruction of the Sclerotinia lettuce pathogens in soil using the least amount of water. A research trial currently in progress will reveal whether or not this is possible. Although summer soil flooding may not be appropriate for all ground planted to lettuce, when feasible, this cultural practice can be an effective component of an integrated disease management program for Sclerotinia lettuce drop.

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To contact Mike Matheron go to: matheron@ag.arizona.edu.