23 February 1996

Disease forecasting service sounds warning of septoria

By Charles Abel

DIAGNOSTIC testing of cereals for disease before visual symptoms show is bringing big benefits to the cereal industry, claims a key proponent of the technology.

Not only has it helped focus eyespot fungicides more accurately, it has also sounded a warning about a possible Septoria nodorum "time-bomb", says Andy Selley, product manager for DuPont.

"Early last year a lot of people were worried about widespread stem base browning. People were talking up the need for eyespot sprays," he comments. "But we predicted a moderate year and that is just what it was." Growers who listened could have saved £6/ha (£2.50/acre) – the difference between eyespot and general first spray rates of Punch C (flusilazole + mbc) and Sportak (prochloraz).

The forecast was made possible by diagnostic tests on over 2000 winter wheat samples. Each test involves selecting 30 stem bases for each 10ha of crop at growth stage 30-32, and sending for analysis. Enzyme technology reveals the level of inoculum present.

"This sort of analysis has helped us track the progression of disease right across the country," notes Mr Selley. The service is now in its fourth year and will once again issue advice to local merchants and involved growers this year.

The test can also track the development of Septoria tritici and Septoria nodorum and has revealed a worrying trend for the latter. "Each year for the past three years S nodorum levels after winter have been higher. Fortunately, we havent had the warm, moist springs the disease needs. If we did we could have a very serious situation."

Not only does the disease develop twice as fast as Septoria tritici, but most varieties have poor resistance to it and most fungicides are weaker on it than Septoria tritici.

If this spring is warm and moist, growers may need to modify their septoria strategies, he says. In UK trials and field experience in France, where S nodorum is more prevalent, flusilazole has been more effective than other products, Mr Selley claims.

&#8226 Diagnostic testing will also be used to check the significance of canopy structure in the transmission of septoria disease, the role of sexual dispersal of eyespot inoculum and the impact of locality on the development of cereal diseases. &#42


DIAGNOSTIC TESTS


&#8226 Checks eyespot and S tritici/nodorum levels in wheat.

&#8226 3 years experience.

&#8226 2000 tests a year.

&#8226 Forecast last years moderate eyespot risk.

&#8226 Warns of S nodorum threat if warm/moist.