Fungicide delays mean a change of programme needed

1 May 1998




Fungicide delays mean a change of programme needed

By John Allan

LIKE many farms around the country the Cereals 98 host, Haverholme Farm Partnership, is way behind with targeted wheat fungicide sprays.

"Unsprayed controls on our Cereals 98 plots of Brigadier have Septoria tritici high up the plant and are showing mildew and yellow rust as well," says Velcourt manager Chris Redfearn. Unfortunately some tramlines are full of water, so an early start to re-spraying looks unlikely.

All commercial crops of Reaper and Riband had an early reduced rate fungicide which has held disease at bay to date. "But we are going to be up to two weeks late with our top-up sprays and we will have to change our thinking on the programme," says Mr Redfearn.

"I am worried about the dilution factor as the plants grow, even with persistent fungicides. We will need to get the right kick- back products to mix with the preventatives. I wonder how people who favour holding treatment until GS 37 (flag leaf just visible) are going to fare this year." Early crops of barley are already at that stage. An early application of chlormequat growth regulator with a reduced dose fungicide has kept the crops clean and strong. But an untreated trial is rampant with wet weather diseases, especially net blotch.

A fungicide and late regulator tank mix will be applied as soon as the weather and workload allow.

Soil nitrogen tests showed residues rather lower than Mr Redfearn expected – 60kg/ha after rape on light land, 75kg/ha on heavy land after second wheat and 81kg/ha on the Cereals 98 site after oilseed rape.

The latest liquid N top dressing to the wheat went on at the end of March/early April and crops look well.

Roots catch nitrogen

A further application will be made to second wheats when conditions allow. "I hope the dry weather and warm soil temperatures in February have got the crop roots down to catch N that has washed down our heavy soil profile."

When the sprayer gets going he prefers to move from wide tyres to intermediate 17.5s rather than go straight on to row crop wheels. He believes this cuts the risk of deep wheelings and secondary tillers.

With a lot of spraying still to do the Sands self-propelled sprayer will be working at 100litres/ha to get a good work rate. "We fitted new Driftbeta nozzles just before the weather broke. The pattern looks very different, much coarser, but there is less drift and they seem to give a good visual coverage on the leaf." &#42

HOST FARM UPDATE

&#8226 Wet weather spray delays.

&#8226 Most crops had T1 OK.

&#8226 T2 plans need rethinking.

&#8226 Fast growth diluting persistence?

&#8226 100l/ha rate speeds work.

Wet conditions and vigorous crop growth on the Cereals 98 site are making for a challenging spraying season, notes Velcourt technical director, Keith Norman. This Rialto shows a clear height difference between pgr-treated (foreground) and untreated.


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