It's a priority

ADAS consultants in East and North Yorkshire.

MOST wheat crops are now at GS 30, with a few crops at or approaching GS 31, whilst the late sown crops are now all tillering. Winter barley crops are very similar to the winter wheat in that many are at GS 30, and the bulk are likely to be there within the next week.

Growth regulator application is now a matter of priority where lodging is a risk.

Most cereals have now had a small amount of nitrogen except some very lush and thick first wheats where no early N will be needed. No more nitrogen should be applied until after tillering is complete and stem extension has started.

The low price expected for grain has led us to reduce the optimum level of nitrogen application. In general, first wheats, after rape peas or beans, should have 140 units/acre (175kg/ha) and second wheats 160units/acre (200 kg/ha). This level must be adjusted for crop condition, soil mineral nitrogen, organic manure applied and your historical knowledge of the field.

With crops at GS30, and actively growing and green, or having nitrogen applied where yellow, the conditions are ideal for getting a good response from PGRs applied in the next week or so. There are more forward, thicker crops than for some years but with low forward grain prices every extra or new cost has to be justified. I prefer to use simple chlormequat at this early stage and follow up with Terpal later if the risk of lodging is high.

Chlormequat products act by reducing the growth-promoting activity of the plant's endogenous gibberellin production. Gibberellins are produced in greatest amounts when plants are growing actively, hence the need for plants to be growing actively to obtain the best effects. Any remaining weeds should be cleared up by tank-mixing a suitable product with the growth regulator, large cleavers are a priority.

The wheat disease situation remains relatively stable, with no rapid build-up of disease. Stem base browning is quite widespread and needs regular scrutiny so eyespot can be dealt with early if threshold levels appear quickly. Septoria, mildew and possibly a little brown rust look like being the main targets for T1 timing, however it is still to early to apply fungicides to wheat unless the crop is threatened by yellow rust.

Mildew, net blotch and Rhynchosporium will be the main barley disease targets at T1, with the balance between net blotch and Rhycho depending very much on how things change over the next week or two. Barley by comparison requires fungicide earlier and this can be applied with the growth regulator at GS31. Good choices are Acanto or Mantra with Unix added if eyespot or mildew is a problem.

Rape crops are making rapid stem extension growth at the moment and many crops have plants about 40-50 cm tall at the green bud to flower stalks extending stage. A few very forward crops are showing some flowers. The high establishment levels last autumn mean high plant populations are quite common, and the PGR effects of Folicur can provide a useful aid to reducing lodging risk in these crops. In many cases dense crops will just lean and become a self-supporting mass that in some cases is easier to harvest.

Phoma leaf spotting is fairly static or even declining as most of the over-wintering rosette leaves are being shed. Nitrogen fertiliser scorch may well be the most obvious leaf symptom at present. All nitrogen should be applied by the end of March. Light leaf spot is the main concern at the moment as it is clear that high levels of infection are present in some crops, particularly early sowings which have not received an autumn fungicide.

Despite some days with higher temperatures, there are as yet no reports of pollen beetles but with the prospects for more settled weather over the weekend, we would expect the first migrations into crops to start soon. Crops are making rapid stem extension growth at the moment and many crops at the green bud to flower stalks extending stage are at growth stages that can be susceptible to attack from pollen beetles. As always we must emphasise that it is rare for winter crops to hold infestation levels that are sufficiently high to justify treatment. Exceptions are backward crops that are more likely to be at susceptible growth stages when the pollen beetle invasion occurs.

Many bean crops are at 4-5 leaves, and very forward crops are 10-15 cm tall. Plants from deeper-planted seed are only now emerging. Emergence and overall establishment percentages have been good and crops are thick if seed rates were not adjusted to allow for the favourable seedbed conditions. The majority of crops have little or no foliar disease but occasional early sown crops have Ascochyta leaf spotting.

Updated: 10:15 Thursday, March 28, 2002