25 February 2000

EARLY GROWTH ADVICE

Early drilled wheats are all set to race through their growth

stages faster than ever this spring. So what should

growers do? Here Louise Impey seeks some timely advice

BRINGING winter wheat sowing dates forward from October into September will have implications for both pgr and fungicide strategies this spring, agree three top crop consultants.

Not only do growers have to be more vigilant and check crop development 2-3 weeks earlier than usual, they may also need to alter product timings and choices to keep crops clean, they advise.

"Work done at Throws Farm last year showed the variety Claire drilled in the middle of September took 1600 day degrees to get to GS30, which coincided with the last week in March," says Bob Bulmer of Dalgety Arable.

"But drilling at the beginning of September meant the same growth stage was reached at the end of February. So sowing just two weeks earlier can make a big difference to plant development, especially in a warm September."

But later drilled crops compensate with more rapid development, adds Dr Bulmer. "Claire drilled in October and November took 1400 and 1125 day degrees, respectively, to get to GS30. So things do tend to even out as the season progresses."

He admits that it takes skill to identify growth stages early in the year, particularly where the depth of drilling has been variable. "You can get differences within a field, so get off the headland and check plants right across the field. Keep checking for GS 30, because that is when the first PGR should be applied."

Dr Bulmer warns that the typical course of action, starting with a dose of chlormequat to promote root development, can be risky at the earlier timing of late February or early March.

"Growers must be aware that chlormequat does not work at low temperatures, so they need to put an adjuvant with it to make it work. An early application is important to prevent lodging, but do not cut corners by missing out on the adjuvant."

As far is disease is concerned, Dr Bulmer stresses that eyespot is worse with early drilling. "And that is the case even with first wheats. Drilling date and eyespot severity is a far stronger link than the position of the crop in the rotation."

He predicts that mildew and rust will also need watching. "Both were around before Christmas and we are experiencing warmer winters. A pre T1 spray in February or early March will be needed on some crops, especially where mildew is a concern.

"The next timing is then GS32, which traditionally has always been at the end of April. But, of course, it could be earlier with some of these crops."

He says there is a case for using a strobilurin at GS32, to get the most from its protectant qualities. "If you opt for straight triazoles, then keep the rates up."

After GS32, crop development and spray timings start to merge, irrespective of sowing date. "The flag leaf spray timing is nearly always the same. In Norfolk, it is the third week in May."

Although pgr and fungicide use and timings will be different, growers should refrain from altering nitrogen applications, he advises. "Do not put more nitrogen on and do not go any earlier. That would encourage tillering, which is the last thing required. Delay or reduce nitrogen with early drilled wheats."

David Robinson of Arable Research Centres agrees that early drilling changes the development of the crop and warns growers to expect higher input costs.

"The crop is growing for longer, so we have to review the number and timings of fungicides. Plants are more advanced at earlier stages in the season. And as leaves should be sprayed as they emerge for maximum protection, timing decisions have to be reviewed."

Extra expense

ARC results suggest the extra expense is worthwhile. "In our trials yields increased by almost 2t/ha and gross margins rose by £150/ha when the spray programme was altered to coincide with leaf emergence."

The flag leaf will also take longer to emerge from early drillings, as the temperatures are lower. "This exposes it to more risk of disease and there is a long way to go from flag leaf emergence to the end of grain filling. So the T3 spray, which has traditionally been an ear wash treatment, will have a new role."

Dr Bulmer stresses the importance of crop monitoring in early spring. "Inputs must be targeted according to leaf emergence. So forget about what your neighbour is doing and get out into the fields and look at crops. The end of April is far too late to be starting to think about fungicides with early drillings."

In UAP trials last year yield differences of 2-3t/ha were seen when fungicides were timed to coincide with leaf emergence rather than calendar dates, says regional technical adviser Peter Gould.

"Leaf 3 was emerging at the end of March, while GS32 was occurring at the end of April," he recalls. "But waiting to spray until the end of April meant that the leaf was already badly infected, so yields suffered."

In contrast pulling spray timings forward to match leaf emergence gave dramatic results. "Just spraying 2-3 weeks earlier gave huge yield differences. The work needs to be repeated this season, but the initial results were staggering."

He advises growers with early drilled crops to be prepared to make sprays more persistent, as they have to work for longer. "Leaving a big gap between T1 and T2 could be disastrous."

He also recommends the use of a pre-T1 spray to keep disease at bay. "If you are growing Rialto or Soissons, then you need to be even more vigilant. They are faster developing than other varieties, so actions will need to be earlier still." &#42

EARLY SOWN WHEATS

&#8226 Faster development.

&#8226 Monitor crops now.

&#8226 Watch for GS30.

&#8226 Adjuvant with pgr.

&#8226 Rethink fungicides.

&#8226 Big yield responses.

Get ready to spray ….. matching application timings to growth stages will be more important than ever this season, say crop consultants. Fungicide and growth regulator choices may also have to be modified.