Cereal Management Guides and Disease Photo Gallery

Eyespot

Eyespot can penetrate successive leaf sheaths, producing brown lesions on inner leaf sheaths. Yield losses from eyespot can be high, particularly in early sown crops. Severe epidemics in early crop growth stages can cause tiller death. Eyespot lesions that penetrate into stems restrict water and nutrient uptake causing lodging from weakened stems. Even without lodging, severe eyespot can reduce yield by 10-30%.

Assessing risk of eyespot:

Eyespot survives between crops on stubble debris. It can survive being ploughed under and ploughed up again the following season. Even after a one year non-cereal break, wheat crops are still at risk. However, normally wheat crops following other cereals are most severely affected.

Varieties differ in their resistance to eyespot. This should be taken into account when planning fungicide strategies.

To be effective, fungicides must be applied early in stem extension. However, most yield loss from eyespot occurs much later - during grain filling. As the stem extends, lower leaf sheaths die and slough off, particularly during dry weather, carrying superficial eyespot lesions with them. Crops at high risk are best identified by assessing lesions that have penetrated beyond the outer leaf sheath, around T1. Such penetration of lesions indicates that a spell of dry weather is unlikely to halt disease development.

Treatment threshold:

Treatment is recommended if 20% or more of tillers are affected by penetrating lesions. For susceptible varieties (UK Recommended List disease resistance rating 4 or less), in high-risk situations, a lower threshold of 10-15% may be used.

Spraying very early, either as a precaution or in response to diagnostic test, may give good control, However, such tests can be very sensitive and detect superficial infections. The spray may be wasted if the disease declines naturally, as stems extend. Spraying after final leaf 2 (GS 33) has emerged is not recommended, as canopy density limits effectiveness and the disease may be too well established.

Product choice:

The main eyespot fungicides are prochloraz, flusilazole and cyprodinil. Cyprodinil, the most effective fungicide against eyespot, has a relatively narrow disease control spectrum and usually has to be mixed with other fungicides. Several triazoles, including epoxiconazole (particularly in mixture with kresoxim-methyl), and bromuconazole, also have some activity.

Dose:

Fungicides with eyespot activity are reasonably effective, provided they are applied at, or close to, the manufacturer's recommended dose.

Control strategies for eyespot:

Scenario

Strategy/Product

1. High risk crop,
over 20% tillers affected

Cyprodinil is first choice
Prochloraz is second choice

2. High risk crop,
eyespot a frequent problem,
but disease below threshold.

Consider prochloraz or flusilazole as tank mix partner for T1 spray. Kresoxim-methyl + epoxiconazole also suitable.

3. Low risk crop,
eyespot present but below threshold

No specific action required. Consider including an eyespot active triazole fungicide in the T1 spray

Key facts

1. The main stem-base diseases are eyespot, sharp eyespot and fusarium.

2. Eyespot is the most important stem-base disease. It is the only one that warrants specific fungicide treatment.

3. An assessment of penetrating eyespot lesions is a useful guide to likely future eyespot risk.

4. Spraying too early or too late can give little or no economic benefit.

 

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