30 May 1997

Modern chemistry puts rust in the bin

WHEAT growers with yellow rust this season have only themselves to blame, say crop consultants.

The disease, fast hitting unsprayed crops and even some fungicide treated ones, is readily controlled by modern chemicals, they claim. Infections reflect earlier missed spraying opportunities.

Rust hot spots are showing up in Hants, Oxon, Wilts and parts of Norfolk, says ADASs John Garstang. Main problems are in Brigadier and Hussar where growers delayed earlier sprays because of drought and apparent lack of disease, adds Morley Research Centres Doug Stevens.

"I have yet to come across any commercial failure where people have done the right thing." That, in Mr Stevens view, meant applying a quarter to one-third dose of one of the newer triazoles at second node stage (GS32), towards the end of April.

Alto (cyproconazole), Folicur (tebuconazole) and Opus (epoxiconazole) all offer excellent control, he explains.

But prolonged dry weather, lack of yield potential and a perceived low septoria risk persuaded some growers to try to cut costs. "Our philosophy is that £10/ha is pretty cheap insurance which gives you more latitude at flag leaf."

ADASs York-based Brendon OConnor claims currently rusted crops are an admission of failure. "Yellow rust should be confined to the dustbin given the chemistry we now have." Despite 17 wet days in 28 in late April/May, most crops in his area were sprayed as required.

"The only excuse is if you held on too long. If you got caught you have been pushing your luck."

Suffolk-based AICC member Peter Taylor says the only yellow rust he has seen is in a Brigadier crop unsprayed for 40 days.n