Saturday, November 28, 2020

Wildflowers could help control aphid-borne viruses in potatoes

November 3, 2020 by  
Filed under Crops

Sowing wildflowers into potato crops could reduce aphid-carried viruses and offer an alternative to declining access to insecticides for growers.

Trials to discover the effectiveness of growing flower strips in tramlines and headlands to promote natural predator populations to reduce pests are being undertaken in Scotland as part of an Integrated Pest Management (IPM) strategy.

The trials are being led by Scottish Agronomy senior agronomist and potato specialist Eric Anderson. He is working with Scottish Agronomy potato member Jim Reid on Milton of Mathers Farm, Montrose.

Mr Reid, who grows 80ha of seed potatoes, is the AHDB Strategic Potato (SPoT) farm host. The trials are being undertaken with Colin Herron and Colin Ross from McCain Potatoes as part of the four-year SPoT farm project.

‘Excellent reputation’

“The trade for Scottish seed potatoes is reliant on an excellent reputation for virus health, and with the pressures of reduced access to insecticides, whether through regulation or greater resistance in aphids.

“It is more important than ever to look at how we can use biology and targeted chemistry to keep disease at a minimum. We are exploring the roles biology, ecology and evolution play and how we can rethink aphid and potyvirus control on a commercial scale.”

Virus incidence hit a 20-year high in 2019 seed potato crops. A similar situation was evident during 2020. The main culprit is Potyvirus (PVY), and pyrethroid insecticides to tackle the problem are under review by regulators.

In any case, the continuous widespread use of pyethroids could resistance or shifted sensitivity at field rates in non-colonising aphids. There is also pressure from retailers for stewardship that reduces chemical use.

Natural enemies

Mr Anderson has identified species such as cornflower, common vetch and yarrow as highly effective in attracting natural enemies of aphids. These are low growing plants that measure the same height as the potato crops.

At Milton of Mathers, 3m-wide strips of this mix have been drilled between the tramlines, creating floral food resources and a refuge habitat attractive to hoverflies, lacewings and ladybirds.

Mr Anderson says this will create corridors closer to the crop. It will increase biodiversity in a move away from a monoculture system with its high reliance of chemical controls – creating a bigger impact because the predators are closer to the pests.

“We are still refining, to assess whether the species sown and sowing dates have an impact on the value of the strips and whether it supports the types of natural enemies needed to control potato pests and to deliver them to the crop when needed.

“Sowing wildflower mixes or alternatively spreading straw mulch in these blank beds are practical mitigation techniques for early generation seed growers, with a disproportionately higher number of separation zones between the numerous seed stocks.”

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