8 December 1995

Disease low but cost £34m

Official figures confirm what cereal growers suspected – 1995 was a very low disease year. But there are crucial lessons to learn from the unusual season, as

Andrew Blake reports

LEAF diseases on winter cereals in England and Wales last summer were at their lowest levels since joint CSL/ADAS surveys began. Even so, fungi are estimated to have cost £34.2m – not far short of the £38.2 losses for 1994.

Wheat

In wheat the total foliar disease recorded in July on 398 random fields, most of which had been fungicide treated, was lower than at any time since 1970, says survey co-ordinator Bob Polley.

Sharp eyespot and barley yellow dwarf virus (BYDV) were the only diseases worse than in 1994, both more damaging than at any time since 1990. As often, sharp eyespot was "most prevalent" in Wales where nearly one in 10 stems had damaging lesions.

Over a quarter of wheats were hit by BYDV, compared with the 60% in the "epidemic year of 1990". But the value of the damage is unknown, says Mr Polley.

Septoria tritici and eyespot were the most severe leaf and stem base diseases. Even so, tritici was at its lowest level since the dry years of 1989 and 1990, with on average only 0.8% of leaf 2 affected. Only in the north, the West Midlands and Wales was it worse than in 1994.

Moderate or, more rarely, severe eyespot symptoms affected 9.3% of stems, much as in 1994, but less than in the three preceding years. Only two samples had traces of yellow rust, remarks Mr Polley. Septoria nodorum was "nationally of little importance".

Stem base fusarium was found as often as in 1994, but the lesions were less severe. And the dry summer meant fusarium ear blight, on only 0.1% of ears, was as rare as it has been since records for it began in 1989.

Barley

Mildew was the most severe of the foliar diseases to hit barley. But the average level (1.3% on leaf 2) was still the lowest since the surveys started. As with fusarium and BYDV, however, the economic effect is unknown, says Mr Polley.

There was significantly more brown rust than in 1994, but the levels were also very low, he notes.

Overall, net blotch affected 0.9% of leaf 2, as it had in 1994, but in the south-west the figure reached 1.9%.

Dry weather in April and May meant rhynchosporium was less of a problem than in the two previous seasons, being worst in Wales.

There was less eyespot in barley than at any time since 1990. Only 4.6% of stems had moderate symptoms, and just 0.1% had severe ones.

The survey found no severe symptoms of fusarium.

Sharp eyespot, however, was at its highest level since 1989, with moderate or severe symptoms affecting 1.8% of stems.

As with the wheat, there were more signs of BYDV than in the three previous years. A quarter of crops had visible symptoms, against 49% in the "epidemic year of 1990".

Septoria, yellow rust and halo spot, all of which nibbled at returns in 1994, were "non events" last season, says Mr Polley.


Table 2: Barley losses

Winter barley yield loss through disease (£m)

9495*

Eyespot4.41.9

Net blotch1.51.7

Brown rust0.41.7

Rhyncho2.91.2

Sharp eyespot0.20.4

Septoria0.05-

Yellow rust0.01-

Halo spot 0.02-

9.486.9

* Provisional. Based on grain @ £103/t. Source: CSL/ADAS survey.


Table 1:Wheat losses

Winter wheat yield loss through disease (£m)

9495*

Eyespot11.713.4

Mildew7.95.2

Septoria tritici6.34.8

Sharp eyespot1.03.5

S nodorum2.00.2

Brown rust0.30.2

Yellow rust0.1-

29.327.3

*Provisional. Based on grain @ £110/t. Source: CSL/ADAS survey.