Oct 22 2020

Optimise Phoma control with Kantor

Optimise Phoma control with Kantor

With thresholds for Phoma infection being met in many parts of the country, growers are urged to check unsprayed crops & optimise Phoma control with Kantor where fungicide sprays are required.

Phoma leaf spot risk is high

The Phoma forecast at ahdb.org.uk/phoma shows that thresholds are now being met in forward oilseed rape crops of susceptible varieties in many areas of the UK. Field monitoring for thresholds of 10-20% Phoma infection is now crucial to protect yield, particularly with the rainfall infection criteria easily exceeded across the country.

Phoma leaf spot can begin from September onwards with initial symptoms appearing as white-fawn coloured circular lesions / small dark lesions that become dotted with small black fruiting bodies called pycnidia. If uncontrolled, the fungus can grow from the leaf spot to the stem via the petiole of the leaf with brown stem canker symptoms appearing typically 6 months later. Over time the cankers get bigger and weaken the stem, causing lodging and plant death.

For this reason, Phoma leaf spot and stem canker is one of the most important diseases of winter oilseed rape in England and in a high-risk year, can account for losses of 0.5-0.7t/ha.

It is therefore important to keep on top of the Phoma threat, and whilst varietal resistance is the foundation of control, a well-timed fungicide spray is sometimes necessary too.

Risk factors

Proximity to previous OSR crop -The main source of infection is air-borne ascospores released from the stubble/debris of a previous oilseed rape crop during warm humid weather.

Rainfall in August & September – Early epidemics are associated with above average rainfall which favours spore release.

Geographic location – Eastern, Southern & Central areas of England are usually most affected.

Late drilling – Smaller plants are at a higher risk of infection as the distance between the leaf petiole and the stem is shorter, making it quicker for infection to occur. As late drilling tends to lead to smaller plants, late drilling increases the risk of infection. In larger plants it takes longer for the infection to reach the stem, and older leaves may die and fall off before infection takes place.

Varietal resistance – Varieties with high resistance ratings (RL rating of 8 and above) for stem canker will also have good resistance to phoma leaf spot and may not require a phoma fungicides unless the 20% threshold is exceeded.


Crop protection

Fungicide application is important and the first application should be made to crops (RL rating 7 and below) when 10-20% of plants have phoma leaf spot, with a second application planned when re-infection becomes evident (4-10 weeks later). All azoles offer protection when applied prior to infection, curative activity may vary.


On time, effective fungicide application is important to curb Phoma leaf spot infection, so teaming fungicide applications with an effective adjuvant that helps to get on the field in drifty conditions, and optimises fungicide performance, is definitely worth the small investment.

Optimise Phoma control with Kantor adjuvant

Proven to payback 

The addition of Kantor to azole fungicides has been shown to increase yield by reducing Phoma infection and the number of plants that become infected.

Optimise Phoma control with Kantor

Contrast = Azoxystrobin | Kestrel = Prothioconazole


Kantor recommendations to optimise Phoma control

  • Add Kantor to all fungicide applications to optimise performance
  • Add Kantor at a rate of 0.15% of the final spray volume
  • Always add Kantor to the spray tank first before adding plant protection products

Get in touch

Require technical assistance or product information? Please get in touch with our Technical Manager, Stuart Sutherland.

For all other general enquiries, please email or call us at the office. If you’d prefer, drop us a message using our contact form and we’ll get back to you as soon as possible.

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