Disease and pest control takes on heightened importance in a greenhouse. In the closed environment, pests, fungus or mould spores and diseases can multiply and spread rapidly. When the presence of pests or diseases is first detected, empty the greenhouse of plants, thoroughly clean the greenhouse benches and sterilise the soil under the benches. Preventive sterilisation should take place in between planting cycles in a greenhouse. Many greenhouse owners prefer the hot water method for soil sterilisation.
Loosen the soil under the greenhouse benches to a depth of 1 foot with a spade and rake. The soil must be completely dry before you treat it so that it absorbs the hot water quickly.
Move a steam generator into the pathway at one end of your greenhouse. Level the generator and fill the gas tank with fuel. Connect a garden hose to the steam generator and activate the hose. You can purchase a steam generator from a greenhouse supply company or power washer manufacturer.
Plug in the steam generator. The generator tank fills with water, which heats to temperatures up to a maximum of 121 degrees Celsius in approximately 20 to 30 minutes.
Position the outlet for the steam generator over the soil. Activate the generator. The hot water will run out of the hose and onto the soil. Continue to pour water over the soil until the soil is so saturated that water stands over the soil surface.
Allow the soil to dry and the water to drain and evaporate. The soil is sterilised at this point.
A plastic cover over the soil is not required in a greenhouse. Plastic covers are required for outdoor soil sterilisation.
The water that emerges from the machine is heated to boiling point. Take precautions that you are not burnt by steam or hot water. Leather gloves and boots as well as insulated, water-repellent clothing should prevent injury. Pad the hose with a burlap cloth if you carry it over your shoulder to prevent a contact burn from the hot hose. A temperature above 110 degrees Celsius can kill beneficial bacteria in the soil.