Cover-crop project aims to tackle nematodes in potatoes and daffodils

free-living nematode damage in potatoes.

A THREE-year project is underway that seeks to mitigate the spread of plant-parasitic nematodes in potatoes and daffodils by utilising cover crops.

Narcissi are susceptible to a variety of pests and pathogens. Stem and bulb nematodes cause foliar lesions and bulb decay.

See also: Ag-tech solution to optimise marketable potato yield

Root lesion nematodes can stay in the soil, causing issues in future rotations not only for narcissi but reducing yield and quality in following crops of cereals, oilseed rape and potatoes.

Potato cyst nematodes (PCN) are increasingly challenging for Scottish seed potato producers, with surveys suggesting 41% of ware potato fields in the country are infested with PCN.

Science and Advice for Scottish Agriculture (SASA) has recorded a 187% increase in land infested with Globodera pallida between 2010 and 2021.

In 2021, 15,737ha was infested with G. rostochiensis.

Transmission

While the two species of PCN do not directly affect narcissi, they are a significant concern to the bulb industry as the cysts can adhere to soil and attach to bulbs, potentially acting as a source of transmission.

The presence of PCN cysts, alive or dead, poses a phytosanitary risk and can prevent the valuable exports of bulbs.

Grampian Growers and Scottish Agronomy, alongside the James Hutton Institute, Harper Adams University and HL Hutchinson Ltd, have begun a three-year research project looking at sustainable ways to suppress pests and pathogens using cover crops.

Management

Most nematode management strategies are pre-cropping treatments, and the planting of cover crops, which are grown between harvest and sowing the next main cash crop, can reduce nematode populations.

The field trials will evaluate brassica biofumigants and nematode trap crops which are ‘poor plant hosts’ that can significantly limit nematode multiplication and substantially reduce existing soil populations.

A vital part of the trial will be ensuring that beneficial non-target organisms are not affected or soil function reduced.

Non-target species

To that end, the James Hutton Institute has developed molecular tools to characterise beneficial nematode and microbial communities fully and will be using its cross-section of methods to assess soil function and non-target community composition in the glasshouse and field trials.

“Performance is dependent on a variety of agronomic factors which we will be exploring,” explains PhD student, Vongai Chekanai, who is leading the research in Scotland, as well as carrying out experiments in England and the Isles of Scilly.

“We know, for example, that French marigolds increased bulb yield in root lesion nematode-infested sites on the Isles of Scilly, but it doesn’t work for all species of nematode infecting narcissus.”

Uncertain future

Eric Anderson, senior agronomist at Scottish Agronomy, added: “Plant-parasitic nematodes are microscopic and difficult to control because they live underground or inside of plants.

“They can seriously damage or even kill crops, but there is no widely available varietal resistance and only limited agrochemical options to treat the nematodes infecting narcissi, some of which are facing an uncertain future.

“Here in Scotland, we are seeing a rapid rise in land infected by plant parasitic nematodes, posing a very real threat to growers.

“Through this project, we are looking for the most robust alternative solutions through IPM [Integrated Pest Managment] to secure the future of the bulb and potato growing industry.”

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