Sanitizing surfaces is a critical step for greenhouse and nursery sanitation. This is particularly important for sites where disease was a problem in previous crops. Pathogens that cause plant disease can survive in debris, in soil, or on surfaces. Cleaning and sanitizing greenhouses, benches, containers, and tools are important steps in eliminating microscopic propagules that can cause disease in subsequent crops.
Greenhouses and nursery pads should be fallowed (emptied) after each crop cycle or at least once per year for cleaning and sanitizing. Begin by removing weeds, carryover crops, and other potential reservoir hosts. Next, clean and sanitize all surfaces (greenhouse sidewalls, floors, and benches; containers; tools; equipment; irrigation lines) in order to inactivate any remaining propagules.
Cleaning Steps
Steps to cleaning containers, equipment, and surfaces include the following:
- Sweep or brush floors and surfaces to eliminate dry debris and soil particles.
- Wash surfaces. Use a brush and heavy stream of water to dislodge large particles. Follow up with soap or detergent. Tools, containers, benches, and equipment should be brushed or rubbed to clean surfaces. Note: Organic regulations indicate that soaps cannot come into contact with food products.
- Rinse away detergent and debris. Repeat steps 1 to 3 until all surfaces are clean.
- Sanitize surfaces, especially if disease was a problem for previous crops. The key to effective disinfection is the length of time the product contacts surfaces; slow-drying increases contact time and optimizes effectiveness. Commercial products are formulated and tested for stability, residual activity, safety, and sensitivity. Refer to label for specific instructions.
- Flush irrigation lines with disinfectant to remove propagules that may have moved into water lines and emitters.
Sanitizers and Disinfectants
Commercial products are recommended for efficacy. The following is a summary, only; refer to product labels for detailed instructions. Mention of trade names is solely for the purpose of providing examples and does not imply endorsement.
- Hydrogen dioxide (ZeroTol® 2.0, Oxidate® 2.0) – effective against algae, bacteria, and fungi; contact time 1 to 10 minutes; use on containers, greenhouse walls and floors, foot baths, tools; use with a foaming agent for vertical surfaces (OMRI listed).
- Hydrogen peroxide & peroxyacetic acid (Sanidate 5.0®) – effective against algae, bacteria, and fungi; contact time 1 to 10 minutes; use on containers, greenhouse walls and floors, foot baths, tools; use with a foaming agent for vertical surfaces (OMRI listed).
- Quaternary ammonium compounds (Green-Shield®, Physan 20®, and KleenGrow™) -effective against algae, bacterial, fungi, viruses; contact time 10 to 15 minutes; residual activity several hours; use on containers, cooling pads, greenhouse walls and floors, foot baths, irrigation lines, tools; foaming formulation (OMRI allowed if measures are taken to assure that residues do not come into contact with the fruit or harvestable tissues).
- Chlorine bleach (10% to 20% dilution) – extremely effective against algae, bacteria, fungi, and viruses; contact time less than 1 minute to 15 minutes; most effective product for use on porous surfaces such as wood, especially at higher concentrations; highly corrosive to metals; damaging to soft plastics and rubbers; dangerous to human health; never mix bleach with products containing ammonia or acidic products; half-life 2 hours (OMRI allowed in certain circumstances).
Alternative sanitizers and disinfectants; efficacy data not available and limited information is available for commercial applications.
- Alcohol (70%) – practical for use on tools; contact time 10 to 15 minutes; flammable (OMRI allowed for disinfestation of tools).
- Trisodium phosphate, TSP (10% solution) – corrosive to metals; harmful to human health (not allowed by OMRI).
- Lysol® Disinfectant, concentrate – practical for containers, tools, equipment, and for hand-washing smaller surfaces (not allowed by OMRI).
Additional Resources
- Greenhouse Sanitation (PPFS-GH-04)
- OMRI Regulations (link)
By Nicole Gauthier, Plant Pathology Extension Specialist
Kentucky Pest News 