9 August 2002

Spraying tips for early drillers

IF you plan to drill wheat early and want to stay on top of septoria it may pay to modify your T1 fungicide treatment, in case T2 gets delayed.

That is the message from Bob Mills of Banks Cargill, who found Acanto (picoxystrobin) usefully more persistent than other T1 strobilurins after this seasons crops came under high disease pressure in the spring.

His findings are drawn from an extensive company trial at Little Staughton, Beds of 13 varieties examining different seed rates and sowing dates overlaid with a range of nitrogen, pgr and fungicide treatments.

"Seed rates didnt seem to make much difference to disease levels. But there were quite big variations between drilling dates when we assessed levels on the top three leaves in untreated plots in mid-June," says Mr Mills.

Depending on variety there was two to three times as much septoria infection from sowing in mid-September instead of mid-October (see table).

It was the weather-enforced T2 spray delay that highlighted the value of Acanto at T1.

The September sowings received their T1, with leaf three emerging, on Apr 13, and the October drillings had theirs on Apr 22.

"But we could not get back with the T2 until June 1," says Mr Mills. "So there was a 17-day bigger gap than we would have liked on the September sowings."

Where both T1 and T2 were based on half-dose Acanto with half-rate Flamenco (fluquinconazole) overall septoria control was much better than where other robust strobilurins were used with that same triazole partner at T1, he says.

In Consort the average infection after the twin Acanto approach was 5% in the October drillings and 15% in the September-sown plots.

By contrast the Oct-sown plots treated with the other strobs at T1 had 10, 12 and 15% infection and the September ones between 15 and 20%.

"Acanto clearly is not perfect, but its persistency and redistributive systemic activity was apparently a major advantage. Whether we will see that in other years when there is less disease pressure remains to be seen. Also the real proof of the pudding will be off the combine." &#42

Multi-wheat trial

&#8226 Early sowing = more septoria.

&#8226 Big untreated varietal differences.

&#8226 Stretched T1/T2 spray gap.

&#8226 Acanto at T1 edge spotlighted.

S tritici infection (%) in untreated crops in June

Sept-sown Oct-sown

Claire 12 5

Access & Xi19 25 10

Tanker & Consort 30 10

Savannah 40 25

S tritici infection (%) in

untreated crops in June

Sept-sown Oct-sown

Claire 12 5

Access & Xi19 25 10

Tanker & Consort 30 10

Savannah 40 25