16 February 2001


WINTER barley trials run at Rosewarne in west Cornwall by the Kernow Grain co-op showed that under 1999/2000 growing conditions the best margins were obtained using two full-rate applications of fungicide mixes containing strobilurins, even though the treatments were by far the most expensive of the six under comparison.

"We selected widely-grown varieties, and a range of fungicide treatments which allowed us to compare the new chemistry strobilurins against the old chemistry triazoles, and also to try to identify differences between the strobilurins," explains farmer and current co-op chairman Mike Hambly. "We also included a single-spray programme."

There were no untreated control plots because of financial limitations. So the treatment which gave the lowest yields across all varieties was used as the base against which the others were compared.

The T1 and T2 spray timings corresponded roughly with GS31 and flag leaf to awn emergence respectively. The barley varieties used were Hanna, Jewel, and Regina, all grown for feed.

The treatment combinations were as listed in the table, and the costs quoted were based on full retail prices. Application costs were not included.

Effectiveness was judged by the weight and value of grain harvested, valued at £60/t, compared with the costs of the fungicides.

Top performer across all three varieties was the combination of a T1 spray of 0.6 litres/ha of Amistar (azoxystrobin) and 0.4kg/ha Unix (cyprodinil) followed by a T2 spray of 0.8 litres/ha of Amistar and 0.4 litres/ha of Opus (epoxiconazole).

That generated 0.76t/ha more yield than the lowest yielding treatment, worth £45.60/ha, but cost just an extra £29.64/ha, giving a net gain of £15.98/ha.

Second best was the same combination but at a reduced rate (see table). Third was a single application at T1 of 0.75 litres/ha of Landmark (kresoxim-methyl + epoxiconazole), with a gain of £9.41/ha, which was better than three of the five two-application treatments.

"The disease pressure down here, especially Rhynchosporium, is always high," says Mr Hambly. "But clearly in 2000 it was so high that it did not pay to cut application rates." &#42

Barley input trial

Treatment Total Programme Jewel Regina Hanna Average Extra yield over Value of extra grain Margin over treatment

Cost £/ha treatment 3 (t/ha) £/ha @ £60/t 3 fungicide cost (£/ha)

1 £64.40 8.70 8.47 9.10 8.76 0.76 £45.60 £15.96

2 £54.40 8.57 8.24 8.77 8.53 0.53 £31.80 £12.16

3 £34.76 7.87 7.84 8.28 8.00 0 £0.00 £0.00

4 £56.20 8.11 8.25 8.68 8.35 0.35 £21.00 -£0.44

5 £60.75 8.07 7.91 8.86 8.28 0.28 £16.80 -£9.19

6 £36.75 8.09 7.92 8.57 8.19 0.19 £11.40 £9.41

Average 8.24 8.11 8.71


Site: Camborne, Cornwall

Date of Planting: 11/10/99

Date of Harvest: 01/08/00

All chemical costs calculated on

full RRP.

Grower experience

The value of a strobilurin fungicide in controlling Rhynchosporium is well understood by Jon Bond of WH Bond and Sons at Trerulefoot, Cornwall.

"It certainly controls it even when you think its been left too late. Weve kept the flag leaf and awns a lot cleaner with two sprays of Amistar plus mainly Corbel, but where late weve used Amistar plus Opus. Weve also tried Twist in place of Amistar and it seemed pretty good."

The Bonds have long grown only Halcyon winter barley, a variety particularly susceptible to Rhynchosporium. "The main effect of Amistar here has been to improve grain quality. Thats important with it all being sold on contract. Last year we only had to take out about 3% screenings to meet the spec.

"We dont get big yields here anyway and growing for low-N malting we dont use much nitrogen. Last year our overall field average was 5.4t/ha and the best-yielding field gave us 6.53t/ha. That had 0.4 litres/ha of Amistar and 0.25 of Corbel at GS 31 and another application at GS37. On some fields we used 0.3kg/ha Unix with the Amistar.

"In the NIAB variety trials here they got Halcyon up to 6.7t/ha and some other winter barleys varieties up to 8t/ha with more nitrogen than we use.".

Mr Bond did not use any full-rate Amistar. "I havent a big enough potential yield to use full rates." The decision on what rate to apply is made by a compromise between efficacy and cost.

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