14 June 2002

Blight putting heavy pressure on potato men

By Andrew Blake

GRAB every chance to keep potatoes protected against blight, experts were advising earlier this week following widespread disease-triggering Smith periods last weekend.

With blight already reported on dumps in several areas and wet windy weather hampering spraying, fast growing crops are at huge risk where unprotected.

"Spray programmes should start at the next earliest opportunity," advises BPC agronomist Rob Clayton.

ADASs Nick Bradshaw agrees. "Its a tricky season, but now is the best time to clobber blight if we want to keep on top of it."

Three-quarters of the 50 Met Office sites used for monitoring the problem reported Smith periods in the four days to the end of last week, he notes.

Many crops are approaching the explosive phase of foliage growth where slips in spray schedules will soon allow the disease to gain a toehold, he adds.

"If its more than a week since the last spray, get on as soon as possible."

Keeping up with programmes has been very hard, reports Hamish Farmer, manager at Honingham Farm, near Norwich. "The weather has been extremely frustrating – wind, rain and more wind. But we have caught up now."

Despite normally ample spray capacity for the farms 364ha (900 acre) processing and packing crop, some cereal treatments have been delayed to allow potatoes to take priority.

The tight programme of Riposte (cymoxanil + mancozeb + oxadixyl) or Curzate (cymoxanil + mancozeb) has so far kept blight at bay, he notes.

It is not just dumps that act as blight sources. Last year ADASs Denis Buckley found unsprayed headland volunteers from a crop five years earlier effectively acting as a ring of potential infection. &#42