TH E WOR LD OF NemaDecide Nematodes – eelworms - abound in all soils. Hardly visible with the naked eye but sheer by their numbers they damage crops by attacking the roots and rendering them less effective to acquire water and nutrients. They result in stunted plants and reduced yields. Root knot nematodes – when causing galls at the skin - also reduce quality. We usually distinguish two types of nematodes: cyst nematodes and free living nematodes. Female individuals of the first category when swollen and full of eggs harden their skin, die and the eggs survive for many years in this cyst in the soil. Potato roots exude a chemical that is recognised by the larvae within the eggs and they leave the cyst to infect the roots. Two potato cyst nematodes exist: golden (Globodera rostochienses ) white ( G. pallida). Free living nematodes infecting potato are root knot nematodes (Meloidogyne species and Pratylenchus penetrans. They lay individual eggs in which larvae grow. Without a host crop their survival period is much shorter than that of cyst nematodes. A consortium of eight agri-business companies and Wageningen University currently develop a decision support system NemaDecide that when ready will assist growers to keep all kinds of nematodes at low economically acceptable density levels. NemaDecide capitalises on the results of fifty years of quantitative nematological research in the Netherlands that has been reworked statistically and is integrated in a software package. It also contains a geographic module because soil samples are taken in spatial patterns and may reveal foci with high levels of infestation. NemaDecide requires a substantial amount of data. First, prior to planting the field is sampled. NemaDecide needs to know which sampling techniques of the ten companies offering this service was used. They range from 200 cc from 60 cores per ha to 13 kg from 330 cores per ha. Laboratory counts yield the initial population: Pi. Half of the 270 cultivars of the Netherlands List were tested for cyst nematodes resistance (inability of nematodes to multiply) expressed as relative susceptibility and tolerance (lack of damage done by nematodes). A list of nematicides is needed with application modes e.g. broadcast or row application. NemaDecide contains financial information such as costs of sampling and chemical control. Growers can add market information such as expected prices for their potatoes. The government supplies legislative information such as quarantine regulation and chemicals allowed are part and also geographical data such as the exact location of the field. NemaDecide is able to forecast two situations: full field infestation and focus – hotspot – infestation. The decision support system gradually leaves the research and development stage and presently is tested by many growers in the Northeast of the country where starch potatoes are often produced in short rotations with potato grown in the same field every two years. The introduction of resistant varieties late last century dramatically reduced the use of soil fumigants in the area but yields on the whole are still negatively influenced by potato cyst nematodes. A grower puts in the required information and requests NemaDecide what measures to take. Depending on a high initial population the grower my get the advise to grow a very resistant variety, that albeit not very tolerant (so will lead to a predicted yield loss) will reduce the nematode population so that the next crop a lesser resistant but more tolerant variety can be grown. NemaDecide can also forecast what happens when the rotation is widened or when a nematicide is used. The system cannot be used for seed potatoes because they are grown in soils absolutely free from those undesired creatures. ● Anton Haverkort POTATO R E S EARCH NemaDecide capitalises on the results of fifty years of quantitative nematological research in the Netherlands Potatoworld 2006 29 Pagina 28

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