8 March 1996

Dont apply in dry year, says PGRO

AFTER six years of trials across the UK, the Processors and Growers Research Organisation has found "absolutely no evidence" to suggest fungicides are worth applying in a dry year, says principal technical officer Anthony Biddle.

"In 1991 we got an average yield response of 20% with Solara at three sites. In Cornwall, it was nearer 40%. But it rained during the critical flowering and pod set stages," he says. "It doesnt matter where you grow peas – that is the only time we would recommend fungicides."

Growers should assess crops when the first pods are an inch long, he advises. If the weather is changeable, or forecast to be, then an mbc/chlorothalonil mix, a vinclozolin (Ronilan)/chlorothalonil mix or iprodione-based sprays + mbc should be applied at or near full rate.

That will coat flowers and prevent botrytis infecting petal debris which sticks to leaves and stems in wet weather.

"Re-assess 14 days later, and spray if showery weather is expected. Be sure to include chlorothalonil – it is better at controlling mycosphaerella which tends to come in after flowering," says Dr Biddle.

High rates warning

He warns against high seed rates. "Often, in a dry year, the higher the seed rate, the better the yield. But in a wet season, a thick crop is going to be a disaster."

Predicting the season at sowing time is impossible. So PGRO advice is to aim for 60-65 plants/sq m for marrowfats, five more for whites and large blues, and 90-95 for small blues. "You could increase that slightly on drought-prone soils, but not on fertile, moisture retentive soils," says Dr Biddle.

&#8226 Aim for thick, clean crop.

&#8226 Choose fertile soils.

&#8226 Establish 90+ plants a sq m.

&#8226 Apply cheap and cheerful chemistry at first bud.

&#8226 Repeat at mid-flower.

&#8226 Third spray at petal fall if strong growth.