Early sown crops are creeping slowly and steadily towards GS 30, with normally-drilled winter wheat crops getting to 'leaf sheath erect' in increasing numbers.

Winter barley crops are in a similar position although at present they are lagging slightly behind the wheats. Some winter barley crops are looking distinctly yellow where nitrogen has yet to be applied, or soils are particularly wet. Growth regulators will be required soon, stick to the basics full rate Chlormequat at GS 30-31 followed by Terpal if you are particularly worried about an individual crop. This has proved the best programme over many years and there is no need to change.

Thinking ahead to fungicides, there is some debate about where strobilurin fungicides should be used in a spray programme. ADAS trials give a clear story - the two most important timings for strobs are T1 and T2. The flag leaf spray (T2) is not disputed by anyone, but there is still some debate over the need for strobs at the T1 timing. Their application at GS31-32 is partly aimed at disease control, (and in Consort and Riband type varieties it is important that a good triazole is included in the spray to give good eradicant activity against Septoria tritici).

Controlling Septoria tritici at this stage of the crop can have large effects on disease development and can have a marked effect on the dose and timing of fungicides around flag-leaf emergence. As well as direct disease control effects, strobs applied at this early timing can have other effects on the crop. The greening effects of strobs applied at T1 is greatest in the middle part of the canopy (leaves 3 and 4) and this can result in greater stem reserves of carbohydrate and a greater number of grain sites per ear surviving. This gives greater yield potential, which cannot be generated by later sprays.

The leaves in the middle part of the canopy are more important in thinner crops than in thick crops. Thus the many thin crops around this year can respond particularly well to strobs applied early in the season. Do not be lulled into thinking that the later-drilled crops will not respond to strob treatment - they may respond better than the thicker crops. Septoria tritici is very widespread on a wide range of varieties, particularly Consort and Riband but also on Claire. The continuing cold weather has kept mildew levels very low.

Eyespot is present at high levels in a large number of crops. Unix is the product of choice for serious eyespot infection.

In barley Rhynchosporium is now becoming much more obvious in crops and is now the most dominant disease. Net blotch is present but at lower levels. Rhynchosporium can be very difficult to control if it gets established in winter barley crops. Control with fungicides can be disappointing - particularly if single active ingredient sprays are used or low doses applied. Where disease pressure is high a 2- or 3-way tank mix of fungicides will be necessary. Epoxiconazole (Opus) is very active against the disease but it needs the addition of a morpholine and/or cyprodinil (Unix) where the disease pressure is high.

Strobilurins can make a very useful contribution to disease control in barley, with trifloxystrobin (Twist) having the edge for Rhynchosporium and mildew, andazoxystrobin (Amistar) being better on net blotch and brown rust.

The need for treatment early in the disease development is further emphasised where strobs are used.

Planning ahead this year is important as in late springs the crop will move through its growth stages very quickly.

This column is supplied by Derek Knight 01430 861988 and Julie Cartner 01904 491478 who are consultants for ADAS in East and North Yorkshire.

Updated: 09:28 Thursday, April 05, 2001