CropWatch South – Iain Richards, Masstock – 2/12/2011

Disease Problems Come for the Fore

We’re currently doing something I’ve never previously done in 20 years as an agronomist – spraying winter barley in December for mildew. Two weeks back and we were content to leave it to the onset of colder, wetter weather to limit the spread of early infections. But the persistent mildness and lack of rain has certainly put paid to this, with mildew levels in crops on thinner and more manganese deficiency-prone soils, in particular, suddenly romping away to affect 60% or more of the leaf area in some cases.

To protect critical and seriously threatened barley tillers we’ve been getting in with straight or co-formulated fenpropimorph or fenpropidin, adding foliar manganese to help the crops recover and more effectively fight-off the challenge.

While mildew levels have also built-up in more susceptible wheat varieties, their far greater ability to compensate for early leaf losses means they don’t warrant treatment yet, although we may need to treat these too if conditions allow infections to threaten winter survival.

Of far more concern with the wheat are the levels of early yellow and brown rust we’ve also been recording. If we don’t get a decent prolonged period of cold weather, we’ll be starting the spring with very worrying levels of infection in many crops. With this in mind – not to mention memories of 2007 – we’re gearing up to nip any problems in the bud with a robust early T0, prioritising crops that haven’t had the benefit of a foliar-disease active fluquinconazole seed treatment for an eradicant as well as protectant spray.

On the plus side, the past few weeks have enabled us to take full advantage of one of the best early post-em blackgrass control opportunities of recent years, optimising water volumes, nozzle choice and spray quality as well as application timeliness. Just as well given the autumn’s particular pre-planting and pre-em control challenges.

The open early winter has also proved a boon for our primary spring cropping cultivations. We’ve been able to get good glyphosate weed control and set up compaction and clod-free ground nice and early for the frost. All we need now is some cold weather.

Which is also what we’re badly needing for our OSR. This time last year, average soil temperatures in Hampshire were 6oC. But we’re only just seeing them fall to the 10oC needed for the best propizamide and carbetamide activity and persistency.

Although we’ve started spraying our less well developed crops, we’re continuing to hold-off on the more forward ones in the hope of some decent cold weather to shrink their canopies back enough for even soil application. For the best activity too, we’d really like to see lower soil moisture deficits than we have in most cases.

It’s a difficult balancing act and test of nerves. With the sort of dryness we have in most of our

subsoils, though, we look like being able to have a good spraying window yet.