Our new Greenhouse Pest Management App is a pest management reference guide for commercial growers of greenhouse crops and flowers.
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Lewis mites were recently reported on a crop of poinsettias. We thought this previously posted message would be helpful. Geoffrey Njue, UMass Extension.
While some growers clean and re-use pots, trays and flats and it is important to do it properly. Plant pathogens such as Pythium, Rhizoctonia and Thielaviopsis can survive in root debris or soil particles on greenhouse surfaces. If the previous crop had a disease problem, then avoid re-using those containers. It is also a good idea to avoid planting crops that are prone to Thielaviopsis problems, such as calibrachoas, in containers that have been previously used.
It is best to clean greenhouses as they become empty rather than to wait until just prior to the spring growing season. Cleaning early will eliminate over-wintering sites for pests and reduce populations for the next crop cycle. Greenhouse pests will overwinter in weeds and protected areas in unheated greenhouse, especially if the winter is unseasonably warm. Remove leftover plants and debris and clean the floor of soil, organic matter and weeds. Clean areas around furnaces and along side walls where small weeds are usually found.
Adult hunter flies are being found on yellow sticky cards, especially in greenhouses that are using biological controls. This small fly, native to the Mediterranean region, has been observed in greenhouses in the US and Canada since 2002. Adults perch on a leaf (see photo) and wait for its smaller prey. The adult hunter fly preys on other flying insects, catching them in flight. It feeds on fungus gnats and shoreflies, but also on other flying insects such as leafminer and, to a lesser extent, whiteflies.