Proposed EU pesticide approval legislation could add £14-25/ha to a typical weed control programme, and if more stringent restrictions were passed, potato crop gross margins could halve from the loss of key nematicides.

Those were two of the conclusions from Potato Council-commissioned studies of the potential impact of the controversial legislation on typical, but hypothetical, potato farms.

Two key residual herbicides – linuron and pendimethalin – will, according to the Pesticides Safety Directorate impact assessment, be under threat from the Commission proposals already agreed by EU agricultural ministers.

A number of alternative herbicides – metribuzin, prosulfocarb, clomazone and rimsulfuron – would still be available, as would alternative methods of weed control, says the council’s Rob Clayton.

“But each has disadvantages,” he adds. “Most must be used pre-emergence and conditions are not always right for good residual activity. The exception is rimsulfuron, which can’t be used on seed.

“Some will require shoring up with a contact product and others, like metribuzin, will be tricky to manage on lighter land where the potential for crop damage increases considerably.”

sprayer spraing spray

Overall, it would make weed control more expensive, potentially adding £14-25/ha to costs. But good control would be possible, he says. “Although there is a strong likelihood many crops of intolerant varieties, such as Maris Piper, would have to progress without good residual protection.”

The weed competition that would result from a loss of residual protection would typically reduce gross margins by £1300/ha, the report calculates.

The European Parliament’s proposals would be even more damaging, particularly for growers with potato cyst nematode problems, because all currently approved nematicides would be removed from the market.

For the hypothetical model farm producing 40ha of potatoes with PCN egg counts ranging from 0.1-25 eggs/g of soil, the impact of losing nematicides would be a halving of gross margins from the first potato crop from £2834/ha to £1344/ha. The second potato crop grown on a five-year rotation would just break even, and the third would make a loss as PCN populations increased. Yields by then would be less than 10t/ha, says Dr Clayton.

Alternative strategies for PCN control exist, but “might be difficult for growers to swallow”, he adds. These include widening rotations to 12 years, but assume good volunteer control in the interim years, which itself might be more of a challenge because glyphosate could come under threat under the proposals.

Also, resistant varieties, particularly for Globodera pallida nematodes, are difficult to breed for, while trap cropping without set-aside present a greater economic burden for farmers, he says.

“Other options, such as steam sterilisation and biological control, may help in the future, but it is difficult to envisage how they would fill the void in the expected time-frame.”

The case studies have been sent to leading potato companies, such as McCain and Frito-lay, as well as interested parties lobbying against the legislation. An interim report from a more detailed study on the impact on potatoes being produced by ADAS will be published in November.