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    Posted 30 January 2004

    THE ON-FARM COMPOSTING NETWORK at Harper Adams University College recently received a call from a potato grower who had been asked by a potato processor to put back the solids from the potato washing process on to his land. The grower was concerned that this may spread diseases and pests.

    Simon Jones, Manager of the On-Farm Composting Network commented:

    “The grower was very worried about the potential for the spread of pests and diseases from this type of soil waste. Being mostly soil this is very difficult to compost.”

    Dr Patrick Haydock, Reader in Nematology at Harper Adams commented:

    “The grower is right to be concerned. The soil immediately around the potato tuber and roots is likely to have the highest concentration of soil-borne diseases and pests. Soil removed at both the field grading and factory washing stage is potentially infected with the organisms that cause potato-early-dying disorder (Verticillium), common and powdery scab, gangrene, dry-rot, stem-canker and black-scurf (Rhizoctonia) if the crop suffered from these diseases. With approximately two-thirds of potato land infested with potato cyst nematodes it is also likely that the soil contained the hardy survival stage, the cyst, which can readily survive grading and washing processes.”

    “If at all possible growers should avoid putting the soil from graders and the sludge from washing tubers back on to arable land. If this is not possible then it should be put back into the field from which it came. This is possible for grader waste, but not from factory washings which may be from a variety of sources.”

    “Putting waste soil back on to other fields means that new diseases and pests may be introduced into `clean fields`. We have observed this with potato cyst nematodes when fields have been mapped for the nematodes` presence and new infestations have been found where soil waste has been dumped.”

    “The problem can be more serious for potato cyst nematodes as they very persistent, being present in the soil throughout the rotation, and can be moved in soil at any time. For growers with sugar beet in their rotation, grader waste from the beet may contain both PCN and beet-cyst nematode cysts.”


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