From Botrytis to Thielaviopsis, diseases on greenhouse plants threaten to wipe out your most valued investment. This could equate to tossing a few impatiens or, worse, throwing out an entire crop. There’s a reason for the saying cleanliness is next to godliness — you need to be religious about greenhouse sanitation.
“Starting clean and staying clean is important,” says Paul Pilon, horticultural consultant and owner of Perennial Solutions Consulting. “Most greenhouse growers are good at sanitation when bringing plants in, but can’t keep it up throughout multiple production cycles.”
The best way to ensure everything starts clean is to tackle an empty greenhouse. Everything from pots and containers to benches and equipment needs to be sanitized with products containing active ingredients like quaternary ammonium, hydrogen dioxide or chlorine dioxide. This process should be repeated between crop cycles.
“Start from ground zero and go from there,” Pilon says. “Any time there is an opportunity to clean benches, we need to take advantage of those windows of opportunities.”
Once the greenhouse interior is cleaned and ready for plants, be sure to inspect for problems such as leaf spotting or pests. Some sanitation guidelines suggest checking every 100 plants or every five to 10 feet on
Be sure to pay special attention to crops that require a high level of sanitation such as geraniums. Pilon also mentions that some articles suggest quarantining the problem crops, but such extreme measures may not be necessary.
“It’s not cut and dry. Different crops need more sanitation,” Pilon says. “Many growers have observed a problem on the incoming line but did not deal with it right away. Be proactive instead of reactive.”
The propagation areas and sections where there are a lot of plants require some of the highest levels of cleanliness, Pilon says. Plants and dirty equipment should be kept off the greenhouse floor or other contaminated surfaces.
For the most part, growers should not reuse flats. If you are reusing flats, be sure to wash and disinfect them between cycles. Soil, however, should never be reused.
“Reused soil is a big area of contamination.” Pilon says.
To ensure contaminated soil does not infect new soil, the greenhouse should be swept and the areas underneath benches, containers and equipment should be cleaned and sanitized. Hoses and water left on the floor also act as breeding grounds for bacteria, so hose hooks should be installed and water cleaned up.
To ensure success with your sanitation program, the best approach is to remain vigilant about cleaning procedures.
“I think we miss a lot of what’s on the materials we bring into the greenhouse,” Pilon says. “Know what you have and head off any problems before they magnify in the greenhouse setting.”