27 February 1998

NEW WEAPONS IN WAR ON POTATO CYST NEMATODES

Waging war on potato cyst

nematode is a perennial

challenge for many potato

growers. This year a new

nematicide and some new

approaches to application

could help turn the tide.

Brian Lovelidge reports

AN ESTIMATED 20% of the 177,000ha (437,367 acres) cropped with potatoes in the UK is infested with potato cyst nematode, increasing production costs by £296-£346/ha (£120-£140/acre).

In the worst affected areas, notably Cambs, Lincs and Norfolk, the figure rises to at least 40% infestation, with up to 100% on some farms.

An integrated strategy of chemical and cultural control is advocated to combat the pest. But is the war being won?

Kevin Price, business manager of ISK, which is launching a new nematicide this year, reckons it is not. "We do not think the size of the PCN problem is diminishing. The trouble is there is less clean land available and this is prompting growers to shorten their rotations."

The lack of good quality PCN-free land in the most intensive potato growing areas is forcing growers to use more severely infested land that would otherwise be rested from the crop, says Mr Price.

That view is supported by the increasing area of land sterilised with Telone (1,3-dichloropropene) in the autumn, he claims.

So this years launch of a third nematicide, an OP, is generally welcomed. Like Temik (aldicarb) and Vydate (oxamyl), ISK Biosciences Nemathorin (fosthiazate) is formulated as a granule for pre-planting incorporation. Its use rate is 30kg/ha compared with Temiks 33.6kg/ha and Vydates 55kg/ha.

"Temik is said to give generally better control of PCN than Vydate and we claim that Nemathorin has the edge on both, particularly on silts," says Mr Price. Unlike many OPs it has low mammalian toxicity, he adds.

"Initially it immobilises juveniles, and their continued exposure to the chemical causes mortality. It also significantly reduces multiplication of the pest."

Roger Ward, a consultant agronomist with Fenmarc Produce, foresees a useful role for Nemathorin. "It looks very handy and will have a significant impact on the market when fully available."

"Its mammalian toxicity is a lot lower than that of the other two products and so has greater operator safety. But its control of PCN is just as good too," he says.

The severity of the PCN challenge is demonstrated by Mr Ward. "Quite a lot of our growers with good quality land carrying 80-100 eggs/g are using autumn Telone and often a nematicide too. The Telone costs about £300/acre and the nematicide £120-£140/acre. One wonders whether it might be more profitable to grow something else where nematode infestation is that high."

Mr Ward points out that his growers are trying to cut nematicide use and target them more accurately by using GPS mapping and more intensive soil sampling.

WAR ON NEMATODES

&#8226 20% of potato crop infested.

&#8226 Add £296-346/ha to costs.

&#8226 Does integrated control work?

&#8226 Growing clean land problem.

&#8226 New OP nematicide Nemathorin from ISK welcomed.

&#8226 Applications in line with GPS-mapping may help.