Empty greenhouses between crop cycles give growers an ideal opportunity to make a clean start for the coming season. Good sanitation practices now will help get crops off to a healthy start, and will encourage good sanitation behaviors throughout the season. Cleaning greenhouse walls and ceilings will increase the amount of light reaching your crop. And for growers who retail their crop in the same greenhouses where they grow, good sanitation gives customers a positive impression of the business and the quality of the plant products.
Sanitation begins with cleaning up crop debris and potting media from previous crops. Decaying plant tissue is a source of plant pathogens and it should be removed from the greenhouse completely. Old potting media can also harbor pathogens and weed seeds, and can be a place for insects to develop, such as thrips pupae and fungus gnat larvae. Weeds must be controlled within greenhouses and nursery overwintering houses. The weeds can serve as a reservoir for pathogens and provide harborage for insects. Weed seeds can also be spread into your crop, increasing your labor expense and decreasing profits. If you do not have concrete floors, commercial weed block fabrics are one effective method for reducing weeds in greenhouses and are easy to install in empty greenhouse. Herbicides are another method for weed control in greenhouses, but there are a limited number of herbicides that are labeled for greenhouse and overwintering house use. Find more information on which herbicides can be used in your greenhouse.
Algae are also common in greenhouses on floors, walls and cooling pads. Algae can make walkways slippery and hazardous to employees and customers, and provide food and breeding sites for shoreflies. Algae problems can be resolved sometimes by improving drainage, removing crop debris, and allowing surfaces to dry. When those actions do not resolve an algae problem, one of the sanitation products listed in Table 1 may be needed.
There are a variety of sanitation products available for green industry use. A list of the most common chemical groups of sanitation products is listed in Table 1. Before using these products you must physically remove all waste and debris because organic matter inactivates some of the sanitizing chemicals or they may simply inhibit the ability of the product to physically contact the surface. Read the product label carefully and be sure to use the product for the amount of time listed on the product label. Not keeping a surface or a tool wet with the sanitizing product long enough will cause the treatment to be ineffective. The treatment time needed varies from product to product and from surface to surface.
There are also many commercial cleaners that are made for greenhouses, evaporative cooling systems, greenhouse glass and plastics, and irrigation systems. These include Floralife Strip-It® Cleaner, Pace Strip-It (active ingredients sulfuric acid & ammonium bifluoride) which can be used on greenhouse structures and irrigation systems to remove whitewashes, organic sludge, oil, dirt, grease, calcium and hard water deposits. The products are for end of season clean-up use only. Other Irrigation line cleaners include Line Blaster® and Line Blaster Organic® (active ingredient Dioxidane ). These will also help clean out irrigation line buildup. Contact your local extension educator or the author for help with understanding your option for cleaning products for specific situations.
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Hose in a cut and sanded PVC pipe designed to keep the hose ends off of the floor where pathogens may be lurking.