Kate Everts, Vegetable Pathologist, University of Delaware and University of Maryland; keverts@umd.edu
As vegetable transplant production in greenhouses gets underway, remember that the potential for disease can be minimized by using certified, tested, and treated seed. Sanitation is the most important management practice. Walls, benches, hand tools, pots and transplant trays should be sanitized with 5% commercial bleach. New potting mix should be used each year. Destroy any volunteer seedlings and keep the area in and around the greenhouse weed free. Once seed is planted, seedlings should be watered early in the day so that the foliage dries quickly and, if possible, watered at the seedling base to reduce moisture on leaves.
Provide good air exchange throughout the greenhouse to minimize periods of high humidity (high humidity favors pathogens). Even after careful sanitation and good practices for managing disease, disease may develop in the greenhouse. Most fungicides are not labeled for greenhouse use. Do not use unlabelled fungicides because the lack of a greenhouse label indicates that there are problems with safety, phytotoxicity, or resistance development risk associated with a fungicide.
The following table, which is modified from the Vegetable Management Guide 2008-2009 New England Region is a good summary of available fungicide options. Please note that Ridomil is not labeled for use in the greenhouse. Please follow label directions carefully.
Please follow link below for table:
Selected Fungicides and Bactericides Labled for Greenhouse Use 2009