Preventive cleaning reduces the risk of pathogens and disease and establishes the baseline for successful biocontrol use. Alarmingly, some growers I’ve encountered don’t practice sanitation at all. So it’s always good to review how to prepare and sanitize a greenhouse after a crop cycle to ensure your next crop is healthy. For the sake of keeping this from turning into a multi-part series, I will assume you at least clean your floors or tables between crops.
It Saves Money. While sanitation adds an expense, it’s a lot less than the costs of ongoing spray applications to treat pests and pathogens introduced and intensified by unsanitary conditions. What could be prevented with a couple of days of disinfecting and starting clean can turn into costly, curative treatments, increased labor for applicators, decreased production time due to re-entry intervals, or worse — incurable plant viruses resulting in crop loss.
It Preserves Structures, Hard Goods, Etc. A grower with wooden benches probably knows what algae and moss will do if left unchecked season after season. The same can be said about fertilizer injectors, boom irrigation, and many other watering systems using an unsanitary source. Biofilm accumulation in lines is one of the leading causes of costly irrigation repairs in older systems.
It’s Safer. I’ve encountered algae patches on walkways that would make banana peels jealous. Add in the usual tangled water hose (also covered in algae) and you’re one viral video-worthy fall away from a trip to the hospital with a work-related injury.
How to Reset After a Greenhouse Crop
Once shipping has finished and the greenhouse is empty, it’s time to start creating a sanitary environment for the next crop.
Don’t Procrastinate. I’m going to assume we all know about common disease and insect vectors (weeds, incoming plant material, tools, etc.). But many growers make the mistake of waiting through the off-season, then cleaning their houses just before production starts. This approach allows many weeds, pests, and diseases to overwinter.
Clean Up the Clutter. Before disinfecting ceilings, walls, benches, or floors in the greenhouse, remove all remaining containers, tools, employee garbage, etc. from the greenhouse. Sweep tables, benches, and floors, and remove and clean all water hoses, sprinkler heads, and other watering devices. Also, use this time to fix uneven spots in the floor or replace missing groundcover.
Weed. Start by manually pulling/digging large and problematic weeds before they go to seed, both inside and around the outside of the greenhouse. Next, apply preferred and approved herbicides (pre and post emergent). Heat treatments are an option for those who wish to avoid herbicide treatments, but soil temperature must be kept at 180°F to 200°F for at least 30 minutes to be the most effective.
Disinfect. There are many products available for disinfecting structures, surfaces, and tools. Some of these products are not licensed in all states, and it is up to growers to make sure they are using an approved chemistry for their jurisdictions. Some of these products can also burn plants and should be applied according to label rates, methods of application, and personal protective equipment requirements.
Start with a thorough pressure washing of all walls, benches, and floors. Pay special attention to problematic areas such as corners and around watering systems where algae and liverwort tend to accumulate.
Strip-It Pro, when applied with a foaming attachment, is a great product that penetrates whitewash coatings, biofilm, mineral deposits, and organic loads without scrubbing. Apply with foamer and allow to sit for 5 minutes before rinsing with a high-powered hose.
Next, apply an antibacterial disinfectant to all walls, surfaces, and floors before closing the doors and windows for at least 72 hours. You now have a clean and sterile environment to start your next crop in. If you plan to leave your greenhouse empty all winter, repeat the last step before starting the new crop.