16 March 2001

CROP HEALTH CHECK – EYESPOT

EYESPOT is the UKs number one cereal disease – and its incidence is increasing. Official figures show that over the past 10 years it has caused a greater economic loss than Septoria tritici.

On average, one in five fields would benefit from eyespot control. But far fewer are actually sprayed. Work by ADAS last year indicated yield losses of up to 34% in wheat without proper eyespot protection – equivalent to £183/ha in a 9t/ha crop.

To help prevent these sorts of losses in your wheat and barley this year, farmers weekly and Syngenta have teamed up to bring you this simple eyespot Crop Health Check.

No varieties are fully resistant. Furthermore, as important as the presence of the disease is during stem extension, it is not the only factor to consider when deciding to spray. Early drilling, large numbers of cereals in the rotation, minimal cultivations and heavy soils can all favour eyespot attack.

Crop Health Check uses agronomic factors to give you an overall field risk. To use it simply consider each field in turn and score the agronomic risk factors present. The total score will help you identify whether the field is at very high, high, average or low eyespot risk.

Combined with checks on 25 random tillers collected from the field and checked for penetrating eyespot lesions, it provides a quick-and-easy guide of whether to spray.

Step One – Agronomic risks

Points

Risk 1 Soil Type A Heavy 3

B Medium 2

C Light 1

Risk 2 Drilling date

A Before 20 Sept 4

B Between 20 Sept and 30 Sept 3

C Between 1 Oct and 15 Oct 2

D After 15 Oct 1

Risk 3 Cultivations

A Minimal 3

B Deep tine 2

C Plough 1

Risk 4 Crop rotation

A Second or more cereal crop 3

B One year break crop 2

C Two or more year break crop 1

Risk 5 Varietal score

A NIAB score 5 or less 3

B NIAB score more than 5 2

Total score

Step Two – Field score

Over 14 points Very high risk of eyespot

Incorporate a specific eyespot treatment within the fungicide programme at GS 31-32.

12-14 points High risk of eyespot

Monitor crops regularly until after GS32. Apply a specific eyespot treatment when lesions are found.

8-12 points Average risk of eyespot

Do not discount treatment until GS33. Monitor crops regularly and treat for eyespot if lesions are found in the crop.

Under 8 points Low risk of eyespot

Treatment is unlikely, but monitor crops regularly until GS33. Treat for eyespot if lesions are found in the crop.

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Two distinct types of eyespot are known to exist – rye type and wheat type (R type and W type).

Research over the past four years has confirmed the more aggressive rye type is now by far the most common. Wheat type infections alone are rare. Consequently, it is important to protect against both types.

Although certain triazole fungicides have eyespot activity, this is mainly against wheat type. Also, the activity of current strobilurins on eyespot is limited. Only Unix – now widely recognised as the best eyespot fungicide available – controls all eyespot species and strains.

In trials, the addition of just 0.5kg/ha of Unix to any T1 strobilurin boosted average yield by 1.14t/ha – worth an extra £56/ha after treatment cost. Where eyespot is identified as a threat, best advice is to use Unix with your foliar fungicide. Dose rate should not be below 0.5kg/ha, and in high-risk situations apply 0.66kg/ha.

As well as take-all, widespread whiteheads in wheat crops last year were also produced by infections of eyespot.

Eyespot lesions at the stem base reduce yield by restricting upward movement of water and nutrients.