12 April 2002

More growers needed to help wireworm trial

POTATO producers willing to try an experimental method of assessing wireworm threat to their crops are being sought by ADAS in a BPC-funded exercise.

"We are hoping to run wide-scale tests of pheremone traps for click beetles, the adult form of wireworms, and are looking for more growers," says Wolverhampton-based entomologist Bill Parker.

The new traps (Arable, Feb 1) offer a potentially better guide to soil-borne wireworm risk than spring bait trapping, he says.

Traditionally the threat is greatest in plantings after grass and long-term set-aside. "But there are increasing reports of wireworm damage in all-arable rotations and we are having difficulty pinning down quite why that is."

Participants will be required to place three traps in a field scheduled for potatoes next year, each containing an attractant specific to the three key wireworm species.

"We would need them to count the beetles caught weekly and change the pheremones monthly. We would then like them to soil sample in the autumn and if they grow potatoes next spring to follow up with a damage assessment."

Wireworms are well known to all growers, but serious attacks still catch out even the most wary, notes the BPCs Rob Clayton.

Even after insecticide use marketable output can be slashed by 25%. "This underlines the importance of sampling," he says.

Click beetles are most active in April and May, and high numbers are known to lead to high wireworm populations.

Although no specific treatment thresholds exist, Mr Parker hopes the new traps may help growers decide better whether they need apply the only remaining product approved for wireworm control in the crop, Mocap (ethoprophos).

"Phorate is no longer approved." Nemathorin (fosthiazate), used against nematodes did carry a manufacturers warranty for wireworm control, but Syngenta says that has been withdrawn.

"It is also very rare to find PCN and wireworms together, and I have never come across both problems in the same field."

Although volunteer growers will receive no specific payment for their efforts, they should be the first to benefit from the findings, suggests Mr Clayton. "They will effectively be investing in their future."

Mr Parker, who has enough traps to monitor up to 150 fields, can be contacted on 01902-693271. &#42

&#8226 New pre-crop pheremone traps.

&#8226 Potentially better guide to risk.

&#8226 Only one approved control product.

&#8226 Volunteer trappers required.