Clean and Green is the Dream

• Take out plant debris by collecting, bagging and removing material. Always keep organic waste bins tightly covered. 
• Avoid carrying over plant material. 
• Remove infected plants as symptoms appear.
• Frequent hand washing and foot baths at the greenhouse entrance.
• Keep containers and hose ends off the floor to avoid contamination.
• Wash greenhouse equipment with detergent.
• Disinfect surfaces such as benches, potting stations, tools and equipment.
• Clean and disinfect irrigation system. 

After you've scrubbed with a detergent to remove large particulates and debris, disinfecting is important to kill the microscopic pathogens that can't be removed with a soap. What's the difference between the disinfectants currently on the market? They fall into several groups described below.

Quaternary ammonium compounds (QAC's) such as Green Shield, Physan 20™ and KleenGrow. These products are stable and are labeled for fungal, bacterial, viral pathogens, and algae. Physan 20 is also labeled for use on plants. They are not protectants and have little residual activity. No rinsing with water is needed. 

Hydrogen dioxide and pyeroxyacetic acid is in ZeroTol, Oxidate and Sanidate. These products kill bacteria, algae, fungus and their spores immediately upon contact. Hydrogen dioxide has a strong oxidizing action and should not be mixed with other pesticides or fertilizers. Oxidate and Sanidate are organic products. 

Chlorine bleach is a common disinfectant, however when mixed with water it has a short period of effectiveness and thus needs to be prepared fresh before each use. Chlorine is corrosive and may be harmful to plastics and metals. It should be used with adequate ventilation. 

Alcohol (70%) is an effective sanitizer that works immediately upon contact. It is often used to disinfect tools, either by dipping  or wiping them down. 

Sound Horticulture has recently added Physan 20™ as an available disinfectant. It controls a wide variety of pathogens on hard surfaces and plants. It can be used in greenhouses, lawn and turf grass, fountains, pools, birdbaths, seedlings and plants. Be aware that it is toxic to fish. Compare Physan 20 to chlorine bleach. 

Advantages of Physan 20™

• EPA approved for use in the greenhouse and on plants.
• Use dilution is very stable, not affected by temperature, light, or humidity.
• 10 minute contact time required to kill pathogens.
• Diluted Physan is safe for use with plastic and metal, even with repeated applications.
• Does not burn clothing if solution is splashed.

Disadvantages of Bleach

• NOT labeled for use as a greenhouse disinfectant by the EPA or at the state level.
• Off label use can result in fines and citations upon OSHA inspections. 
• Use dilutions of bleach are unstable, degrade quickly, and are temperature sensitive. 
• Length of time required to kill organisms is 30 minutes.
• Degradation of plastic and metal after repeated applications.
• Limited residual effectiveness, new use dilutions need to be prepared daily.
• Harms clothing with contact even at use dilution levels. 

Disinfectants can be the difference between a healthy crop and one that gets tossed in the dumpster. Before the first seed is ever planted, implement a plan to keep your growing area clean and free from pests and disease and turn your dream into a reality. Clean and green is the dream. 

Resources

Sanitation is Critical to Prevent Plant Diseases - MSU Extension

Cleaning and Disinfecting the Greenhouse - UMass Extension

Greenhouse Sanitation the first step in Managing Pests and Pathogens - Greenhouse Management

Sanitation Guidelines for the management of pests and diseases of greenhouse vegetables - Ontario