In light of recent floriculture disease outbreaks during the last two production years (see these Michigan State University Extension articles: “Impatiens downy mildew: Outbreaks reported in Michigan and nearby states” and “Common questions and answers about tobacco mosaic virus”), now may be a good time to review your greenhouse sanitation protocols.
Photo 1. Organic plant debris that is left discarded in an uncovered container may be a breeding ground for pest and pathogens that could potentially infect your crop.
A good and easy first step in greenhouse sanitation is to physically remove all crop debris. Weeds, plant debris and unsalable plants can serve as sites for insects and mites to live and for diseases to develop, progress or spread. To properly manage weeds, see “Weeds in the greenhouse: More than unsightly.” Remove all weeds and crop debris and place them in a tightly sealed, covered garbage bin so that pests and pathogens are not able to migrate out of the trash and into your crop (Photo 1). Remember to remove the trash daily. Also, remove spilled media because organic residues from plants and growing media reduce the effectiveness of disinfectants (Photo 2).
Photo 2. Removing plant debris and spilled media from this stone greenhouse bench will make disinfectants more effective.
If you ultimately compost the removed organic material, make sure the compost pile is at least 30 feet away from the greenhouse and not uphill or downwind from the greenhouse (Photo 3). Situating the compost pile in this manner will prevent pests from migrating from the compost pile back to the greenhouse. When removing diseased or infested plants, discard them into containers or bags that are immediately adjacent to the plants and seal the container or bag to transport them out of the greenhouse immediately. In this way, inoculum or insects are contained and not spread throughout the greenhouse during transport.
Photo 3. A compost pile that is situated too close to the greenhouse may allow pests and pathogens to migrate from the pile back into the greenhouse.
Once all surfaces are free of organic matter, consider power-washing structures and walkways with soap and water when in between cropping cycles. Then, clean those same surfaces with a disinfectant. Make sure propagation or pruning tools such as knives, scissors, etc., are properly disinfected after being used on each bench or each variety or cultivar.
(Source – http://www.farms.com/news/greenhouse-sanitation-is-the-first-step-in-managing-pests-and-pathogens-81362.aspx)