Schnitzler - Pest and Disease Management of Soilless Culture

La prevenzione delle malattie nelle colture fuori suolo

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Wilfried H. Schnitzler*
Center of Life Science, Chair of Vegetable Science, Technische Universität München, 85250 Treising- Weihens Tephan, Germany

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Pest and Disease Management of Soilless Culture

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Key words: hydroponics, soilless culture, IPM, vegetables, ornamentals.

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Abstract

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Contrary to cultivation of plants in soil, any soilless cropping system requires a continuous supply of water and nutrient solution open or in closed circultation. Technical set-up of open systems is simple and spread of root infesting pathogens is limited. But excessive nutrient solution runs off causing environmental hazards. Recirculating nutrient solution has ecological benefits but asks for exact crop management. Under certain conditions, pathogens can spread to endanger the entire crop. Nevertheless, today only closed systems should be considered. There are quite a number of different technologies available with more or less risks to damaging plants’ root system due to various pathogens. The choice of substrates for soilless cultivation is extensive but they have always to be free of pathogens when applied first. When reused they must be disinfected. Most destructive are phytopathogenic fungi, such as Pythium, Phytophthora and O l p i d i u m, followed by viruses, bacteria and nematodes. Early on, the grower should take care to only transplant healthy seedlings to avoid problems form the start. Also greenhouse structures can serve as infection sources as well as surface water for irrigation. Soilless cultivation technologies have the huge advantage to optimize growing factors like temperature, water, pH and nutrients according to the plants’ need to reduce stress. Large operations with monocrops may choose sterilization of the irrigation water. There are a number of practical options ranging from various chemicals (ozone, hydrogen peroxide, chlorine, iodine), UVc irradiation, heating, membrane and slow- or bio-filtration. Biological control of root infesting pathogens offers very interesting new approaches, e.g. with Bacillus subtilis strains, S t r e p t o m y c e s , T r i c h o d e r m a, nonpathogenic F u s a r i u m and V-micorrhiza strains besides fluorescent Pseudomonades. Research must open new venues to create an environment in the substrate optimizing growing conditions of such spontaneous or selectively employed beneficial microorganisms.

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