New weapon joins fight against rising eyespot

6 March 1998

New weapon joins fight against rising eyespot

Eyespot control, eased this

spring with the launch of a

new fungicide, remains a

controversial subject.

Brian Lovelidge reports

EYESPOT seems certain to increase if Agenda 2000s proposals are fully adopted. The wheat area will increase at the expense of break crops allowing the disease to proliferate, pundits suggest. But manufacturers remain at odds over its control.

New in the UK for 1998 is Novartiss Unix (cyprodinil) fungicide, with relatively good activity against both wheat (W) and rye (R) eyespot types.

Trials suggest it is the best eyespot product available, giving a yield response of up to 1t/ha where infection is moderate to high, says product manager Neil Waddingham.

"Main holes in Unixs spectrum are Septoria tritici and rusts, so we see it being used with a triazole or strobilurin."

Surveys suggest eyespot is more widespread than generally believed, he says. In 1996 ADAS sampled 40 East Anglian wheat crops at early stem extension and assessed corresponding yield losses. Eyespot was in most crops and severe enough in 35 for cyprodinil treatment to be cost effective. Maximum yield cut was 35%.

Of 50 crops sampled in 1997 only two were eyespot-free. 30 exceeded ADASs spray threshold of 20% plants infected, reports Mr Waddingham. In the worst case all plants were infected, giving a 11% yield loss. Although that was unexpectedly low, treatment would still have been economic, he claims.

By contrast a crop with only 8% plants infected lost 26% of its yield loss because the disease continued to spread. "That sort of occurrence is typical of eyespot and means ADASs spray threshold might be worth revising."

On average only 10% of wheats exceed the threshold and are consequently sprayed, says Mr Waddingham. This season the company will check whether this accurately reflects the scale of the problem.

Two-hundred samples from sites in England and Scotland will be collected, and DNA fingerprint technique will be used to identify the extent and incidence of each eyespot type.

EYESPOT DEBATE

&#8226 Agenda 2000 effect.

&#8226 Disease underestimated?

&#8226 New fungicide control.

&#8226 ADAS threshold questioned.

&#8226 Opinions differ on R & W types.

Eyespot is estimated to have cost UK wheat growers £20.4m last year.

Neil Waddingham: Unix can deliver up to 1t/ha extra yield where eyespot is moderate to severe.