ISHS Acta Horticulturae 695: I International Symposium on Tomato Diseases
DISINFESTATION OF RECIRCULATING NUTRIENT SOLUTION BY FILTRATION AS A MEANS TO CONTROL PYTHIUM ROOT ROT OF TOMATOES |
| Authors: | J.C. Tu, B. Harwood |
| Keywords: | Pythium root rot, hydroponic culture, tomato, filtration, recirculating nutrient solution |
| Abstract:
Greenhouse tomato production is valued at about 250 million dollars annually in southwestern Ontario. The tomatoes are grown hydroponically and mainly in a rockwool pouch system where their root systems are partially submerged in the nutrient solution. Such growing conditions are highly conducive to the development and the spread of Pythium root rot disease because the recirculating nutrient solution can carry the pathogen and spread the disease. Therefore, it is imperative to disinfest the run-off nutrient solution before recirculating it. This paper reports the successful application of leak-proof, micropore, modern filters to remove Pythium zoospores from the recirculating nutrient solution. The two filters used are (a) Membrane Module Filter that consisted of numerous hollow fibre membrane strands and (b) Sediment Filter Cartridge that was constructed with pleated cellulose/polyester materials. The former has a porosity of 0.01 µm which can completely remove zoospores and bacteria, and the latter has a porosity of 0.5 µm which can completely remove zoospores, but not bacteria. Both filters can withstand pressure up to 2.5 kg cm-2 and deliver a flow rate of 50 L min-1. In both cases, a prefiltration using a 20  pore size pleated cellulose/polyester cartridge along with a 100-mesh strainer can drastically increase the life span of the filters.
The filter systems are highly effective and economical and require minimal infrastructure as compared to other disinfestation systems such as UV, heat, ozone, ultrasonication and sand or volcanic lava filtration systems.
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