| | The end of season cleanup is necessary to help ensure the success of next year's crop. A thorough cleanup is an important component of the pest and disease management program as it can prevent or minimize the carry over of pest and disease problems into the next season.
All crop residue is removed from the greenhouse and disposed of. Depending on the area, facilities may exist to accept the crop residue for composting. The spent coir from the grow-bags could also be a welcome addition to compost sites as much decomposition has already occurred during the growing season. Once the crop has been removed, increasing the greenhouse temperature to over 25°C for several days can increase the metabolic activity of any pests still in the greenhouse and can help cause them to die of starvation in the absence of their food source (Portree 1996).
The interior of the greenhouse should be washed with a detergent solution using a pressure washer and then rinsed. The detergent will remove oily residues from the greenhouse and covering material. Following the rinse a registered disinfectant solution can be applied to aid in disinfecting the greenhouse structure of any remaining pests and disease organisms. To avoid a chemical reaction between the disinfectant and the detergent please consult with your supplier prior to purchasing your products to ensure compatibility. When pressure washing the greenhouse ensure that all safety precautions are taken to prevent direct exposure to the bleach solution.
All greenhouse equipment should also be washed and disinfected. Dripper stakes, clips and truss supports (tomato greenhouses) should be soaked overnight in a 10% bleach solution and then rinsed.
The irrigation lines should be flushed with nitric or phosphoric acid at a pH of 1.6 to 1.7 (1 part acid to 50 parts water) (Portree 1996). Do not allow the acid solution to contact the pH electrode sensors or the E.C. sensors as they can be damaged (Portree 1996). The acid solution should be allowed to sit in the lines for 24 hours at which time the lines should be thoroughly rinsed with water to ensure that all the acid solution is removed from the lines.
CAUTION: Provide good ventilation through the greenhouse when flushing the lines with acid to avoid the build-up of fumes. Ensure that the flushed water does not have a pH of below 5 as dangerous chlorine gas may form (Portree 1996).
Steam sterilization of slabs
If rockwool slabs are used as the growing media, they can be used again for the upcoming crop. The reuse of rockwool slabs is both environmentally friendly and makes economic sense (Portree 1996). Good quality slabs can be used for up to three years (Portree 1996). Do not use slabs that have lost more than 10% of their original height (Portree 1996), as this is an indication that the structure or "profile" of the slab has changed such that the yield of subsequent plants grown can be reduced significantly.
Steam sterilization can ensure that disease organisms do not carry over into the next season. Slabs should be as dry as possible as dry slabs heat faster than wet slabs (Portree 1996). If the crop has had tomato mosaic virus (TMV) or pepper mild mottle virus (PMMV) the slabs should be heated to 100°C and held at this temperature for 10 minutes (Portree 1996), otherwise the slabs should be heated to 75°C for 20 minutes (Portree 1996). If the slabs are bagged and paletted, they require 5 hours to reach 100°C (Portree 1996). |
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