North: Crop disease at tolerable levels in Perthshire

As ever weather is the great dictator. Variable conditions from glorious sunshine through to frost and snow have kept crops and advisors guessing this month. Soil temperatures have crawled upwards, so crop growth has generally been on the slow side.

Crops are not as far forward as last year and on the plus side disease levels are still at a tolerable level. However, those crops that have received some early nitrogen are starting to respond. Where wind conditions have allowed, some spraying has taken place.

Oilseed rape fields vary from brown earth, where pigeons have wreaked havoc, to welly boot height. Although light leaf spot levels have not progressed over the past four weeks, spraying to control this disease by the latter growth stage is essential to prevent yield loss.

The local pollen beetle predictor station claims that beetles have started to migrate this week. If that is the case I reckon that they are wearing thermals. If this week’s weather forecast of frost and snow down to low levels is to be believed, then I guess that they may beat a hasty retreat.

Nevertheless, keep an eye open for these pests and be aware of the updated threshold levels for treatment to attempt to slow down the level of resistance to pyrethroid insecticides. If you find winter stem weevil damage there is nothing you can do at this stage. An autumn spray is currently our only defence against this pest.

Winter cereals that did not get a herbicide treatment in the autumn may need a complex mixture or sequence depending upon the weed strength and density. Consult your advisor to avoid any misunderstanding.

Disease levels in cereals are on the low side. However, rhynchosporium and mildew can be found in winter barleys and septoria is easy to spot in most winter wheats. A robust rate of triazole +/- a mildewicide plus chlorothalonil will be the order of the day for most winter sown cereals. A plant growth regulator is unlikely to be required until the T1 spray when a decision about the inclusion or not of an SDHI fungicide early in the programme will need to be made.

Quite a bit of spring wheat has gone in this year to assist compliance with the draconian “Three crop rule”. Pre-emergence control of annual meadow grass will require invoking an Extension of Authorisation for Minor Use (EAMU). On lighter ground spring barleys have been planted in good order. I just hope that the ground warms up quickly. As with wheat the best control of annual meadow grass comes from a pre-emergence treatment.

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