19 February 2000

Step on the brake

Green, lush and racing ahead – whats the best way of keeping these early drilled wheats on the right track? Gilly Johnson asks the consultants.

GROWTH REGULATOR

WINTER? What winter? With temperatures remaining mild throughout January and February, early drilled wheats have become lush and thick. In some cases, worryingly thick.

Most advisers are recommending an early start to growth regulator programmes as an anti-lodging strategy. Wheat sown in late August/early September is now approaching growth stage 30 (ear at 1cm) – which is the trigger timing for growth regulator treatments.

Shown in the table is the average development chart for a range of varieties in Dalgety trials last year; individual wheats will vary but this gives a comparative guide. However, this season is turning out differently. Advisers reckon early drilled crops are well ahead of last year, and are now hitting GS30.

"As GS30 tends to last longer in these forward crops than in later-sown ones, it will be possible to apply a split now, if you havent already, at late tillering to early GS30, with a follow-up later during the GS30 period at the end of February," says ADASs John Garstang.

But not everyone agrees with an early start to growth regulators, even on lush canopies. "Dont panic. Id advise patience," says consultant Simon Draper, with Independent Agronomy.

"Wait two to three weeks. You may not achieve anything if you go any sooner than mid-March with your first growth regulator treatment. When youre using split doses, the crop can quickly grow away from the first spray, before the second is applied.

"Plants will stay at GS30 for a while – development is triggered by day length, not temperature at this stage."

For both, product of choice is chlormequat. "Keep costs down and use the older, cheaper materials," says Mr Draper. "If they go on at the right time, theyll do as good a job." He suggests a two-thirds dose, with a one third treatment about a month later.

"A split is always beneficial – the only exception Id make would be where the crop is very backward."

NITROGEN

Consensus is: hold off. Lush, early drilled crops should not be given early nitrogen, says Mr Draper.

"The risk of increased lodging is too great." Only in the case of varieties with exceptional straw stiffness, such as Equinox or Buster, rated 9 for straw strength, might he be persuaded to make an exception. Crops with a tiller count of 600/sq m or over will manage without early nitrogen, he reckons.

"If plants are already showing between five to six tillers – then whatever you do, dont put on nitrogen until April. Anything less than three tillers, or crops sown at a very low seed rate which are now looking gappy – then perhaps the plant might benefit."

John Garstang agrees that early nitrogen would not be advisable. "In the main, these early sown wheats have developed good rooting structures and are well coloured in the field." Although soil mineral nitrogen figures are "a bit low" following wet weather, on balance early nitrogen could do more harm than good.

Increasing green leaf area through fertilisation would also raise disease risk, he says. "And this year is one where we all want to avoid spending more money than we need on fungicides."

FUNGICIDES

Mildew and septoria are making an early appearance this spring. On varieties where mildew might cause concern, independent consultant Mr Draper will be advising an early low rate spray of Fortress (quinoxyfen); for lower risk fields, a low rate morpholine is adequate.

To clear up severe early yellow or brown rust as well as mildew, a propiconazole (Tilt plus morpholine) type mix is his alternative choice. Where needed, hell be putting the first fungicide on with the initial growth regulator split in March.

So far, no reports of eyespot have been received, but Mr Garstang of ADAS warns that the risk is there: "The mild winter will encourage eyespot in early drilled crops. Start looking now."

HERBICIDES

One benefit of early drilling is that forward crops do a good job of suppressing broadleaved weeds. "Speedwells, deadnettles and similar problems will have been swamped," says Mr Garstang. "Cleavers are likely to be the only broadleaved weed left to tackle."

Early drilled wheat

Wheats drilled in late August/early September may have come through the winter too thick. Aim for a tiller count of 900/sq metre, according to the HGCA Growth Guide

Growth regulator

Opinions differ – some say go now, others say wait until March. But do something, even with stiff strawed varieties. A split chlormequat treatment looks to be the cheapest option. Other products (Moddus, Meteor) may offer greater flexibility on temperature – chlormequat wont work as well in cold conditions

Fertiliser

Hold fire until next month; early nitrogen could exacerbate lodging risk and early drilled wheats are likely to have well-established rooting systems

Disease

Mildew, rusts and septoria are visible. On very susceptible varieties, an early low rate fungicide might be needed. Monitor stems for eyespot, because risk is high; early drilling and the warm winter help disease development

Weeds

Cleavers are the remaining threat. Lush canopies should have suppressed other broadleaved weeds.

A farmer survey in December 99 shows:

&#8226 37% of wheats were drilled before the end of September

&#8226 average seed rate for September drillings was 293/sq m, with a range of 100-593/sq m

&#8226 most popular varieties were Consort (18%); Claire (17%), Malacca (9%) and Savannah (7%)

Source: Novartis

  However, ADAS trials show mid-September drillings can go safely down to an established plant population of 50 plants/sq m: lodging risk rises over 200 plants/sq m. Many early drilled wheats are likely to be above this threshold.


Growth Drilling date

stage 4 Sept 17 Sept 9 Oct 19 Feb

GS30 2 Mar 2 Mar 27 Mar 26 May

GS31 11 Mar 28 Mar 10 Apr 1 June

GS32 3 Apr 14 Apr 1 May 6 June

GS33 13 Apr 1 May 9 May 11 June

GS39 13 May 17 May 23 May 16 June

Source: Dalgety Arable