ISHS Acta Horticulturae 382: IV International Symposium on Soil and Substrate Infestation and Disinfestation
DEVELOPMENT OF OLPIDIUM AND PYTHIUM IN THE NUTRIENT SOLUTIONS OF NFT GROWN LETTUCE, AND POSSIBLE CONTROL METHODS |
| Authors: | A. Vanachter, K.U. Leuven |
| Keywords: | Sterilization, UV, lettuce ring necrosis disease, Lactuca sativa, virus vectors |
| Abstract:
Since NFT cropping was introduced by Dr. Allen Cooper, this technique was used for a variety of crops. One of these is lettuce, for which the work of Benoit and Ceustermans (Research Station of Vegetable Crops, St.-Katelijne-Waver, Belgium) was of major importance. Using these developments, it is possible to grow up to 8 crops of heavy head lettuce on a year round basis. A big problem however is the possible spread of plant pathogens through the whole system. This is already observed for Olpidium brassicae, vector of Lettuce Big Vein Virus and Lettuce Ring Necrosis Disease, and for Pythium spp., resulting in important crop loss. These diseases are a limiting factor for the development of the NFT technique for lettuce growing. Till now, the use of fungicides or other chemicals (surfactants) failed in controlling both fungal organisms. Our research was directed into two different ways, e.g. use of fungicides, combined with zinc, and disinfestation of the recirculating nutrient solution. The first part of the research was done in an experimental NFT system, consisting of 16 individual circuits. After artificial inoculation with an O. brassicae strain, carrying the lettuce ring necrosis disease agent, and treatment of the nutrient solution with thiophanate-methyl and zinc, we could prevent disease development for the whole experimental period (5 crops). Neither with zinc or thiophanate-methyl alone we could reach the same effect. The main problem for the disinfestation of the nutrient solution in a NFT system is the high amount of water in circulation. One must count with about 100 m3.h-1.ha-1. For this reason in a second part of the research we tested a low pressure UV installation (Uvaudes) working on the catchment tank, which means that only a part of the solution was treated. Total sterilization was not obtained, but consecutive crops could be harvested without disease symptoms. | |
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