Rhyncosporium is now a worry

ANOTHER month of poor weather in all areas has caused the now familiar backlog of delayed jobs, from nitrogen spreading, to spraying, to sowing beet, to planting potatoes.

The bulk of wheat crops are now around GS 30-31, with a few of the most forward crops at GS 32, and T1 fungicides waiting to go on. Some T1 fungicides have been applied to barley on the few recent sprayable days but many are still waiting. This is a worry as rhyncosporium remains the main problem.

With eyespot levels increasing, the inclusion of Unix (cyprodinil) has a dual role. It will also give some protection of new growth from rhyncosporium, net blotch and mildew. Trace infection levels of brown rust have been noted in the six-row variety Siberia.

Some crops, however, will be past GS 32 before spraying is possible, and keeping the disease off the upper plant will become increasingly difficult. Even multiple active ingredients at high rates may not give acceptable control.

It is hard to believe, but a warm spell would quickly bring on flag emergence. In some years we have even had awns showing in early May in very forward crops.

In winter wheat, T1 approaches for many crops and the timing of sprays for effective Septoria tritici control will be difficult if the unsettled weather continues. Disease levels remain high on lower leaves and although low temperatures have slowed symptom expression, upper leaves will now be infected, although not showing symptoms.

A few forward crops are now at early GS 32 and high-risk crops will need treatment as soon as field conditions allow. Leaf 3 is starting to emerge and should be kept disease-free if the progress of Septoria up the crop is to be prevented. High risk varieties such as Savannah, Consort and Riband should be targeted for priority treatment. Mildew levels continue to remain very low in the recent cold weather.

As forecast, eyespot appears to be increasing, particularly in early-sown crops, regardless of their place in the rotation. Check all crops for increasing levels of eyespot. Apply treatment, if needed, with the main fungicide treatment at T1. Where eyespot is over threshold the preferred fungicide would be cyprodinil (Unix) although Punch and Landmark both have some activity against eyespot and can give useful control.

Nitrogen applications have been possible during the catchy, windy weather when spraying has not been possible. As a result, quite a few forward crops have already had their main dressing or the first split of it. Those that have not, and are approaching GS 31, should be top-dressed as soon as ground conditions allow.

Stem extension will start quickly and move rapidly. Do not get too concerned with the niceties of the timing of nitrogen. This is not that important once it is May, and there are so many other things that need doing. It is important that the 'decks are cleared,' as far as field work goes, in time for the T1 fungicides on wheat where timeliness is crucial to profitability.

One little piece of cheer to end on, is that late-autumn delivered prices of milling wheat have been creeping up above the £100 level in some areas. Even with premiums strengthening, the final payment will depend on protein and specific weight meeting contract specification, so adequate nitrogen is required. It can often be worth increasing the total N amount to milling crops by about 40kg/ha to help boost protein.

Updated: 10:40 Thursday, May 03, 2001