Manage early Phoma risk
Phoma infection risk is reported to be high in early drilled oilseed rape crops, so now is the time to start monitoring crops to manage early Phoma risk. Trials show Phoma control can be maximised with Kantor in the tank.
Whilst some oilseed rape crops may have survived the dreaded cabbage stem flea beetle, Phoma is being reported in some parts of the country and will need managing to protect yield potential.
Here’s our latest advice to help assess the risks and optimise Phoma control on your farm.
Phoma risk is high
Rainfall and temperature monitoring by ADAS at its regional centres, shows the threshold for Phoma infection in oilseed rape has now been reached at various locations across the UK.
Yield stripping cankers make Phoma one of the most important disease threats to oilseed rape, with penalties of 0.5 t/ha quite common in susceptible varieties. Growers are therefore advised to remain vigilant and to check crops for signs of leaf spot infection.
Crops will be most at risk where:
- Close to previous OSR field with crop residues remaining on the surface – debris is the main source of spores
- Crops situated in Central, Southern, Eastern England
- Field conditions have been warm/wet – conducive to spore release, infection and spot development
- Plants are small – disease movement to stems through short petioles is greater
- Varieties have a Recommended List Score of 7 or less – stem cankers can be more severe
Treat at 10-20% Phoma infection
Fungicide treatment is important to protect crops from infection once the infection threshold has been reached.
The threshold for spraying is 10-20% in varieties with a Recommended List score of 7 or less, and 20% or more for scores of 8 or 9.
Fungicides should be applied as close to the threshold being reached as possible. All azole fungicides offer protection when applied prior to infection, but curative activity may vary.
A second spray may also be needed 4-10 weeks later, should new lesions become visible, so continue to monitor crops.
Phoma leaf spot infection in oilseed rape crop
Maximise Phoma control with Kantor
Add Kantor at 0.15% of the spray volume to reduce Phoma infection & protect yield.
The addition of adjuvant Kantor to fungicide sprays will help to retain and spread the fungicide on to waxy oilseed rape leaf surfaces.
This is vital to maximise protection because:
- protectant sprays do not move on the leaf surface, so any missed areas of the leaf or petioles can easily expose the crop to infection.
- oilseed rape leaves are very waxy, so any application using water as the carrier (which all sprays are of course), will result in high surface tension, leading to poor spreading and retention across the leaf.
Adding Kantor lowers surface tension, allowing the spray to spread out and fully coat the leaves and petioles, maximising protection.
Any fungicide applications made for their curative activity will also benefit from Kantor’s unique penetrating abilities that enable faster uptake.
Trials (see graph – right) have shown that adding Kantor can reduce the percentage of plants infected and Phoma infection, whilst also protecting yield potential.
Other considerations where adding Kantor will help:
- Autumn applications can be drifty, which can delay spraying & reduce deposition on the crop
- The oilseed rape canopy can be difficult to protect as the crop gets bigger and canopies harder to penetrate
- Weeds may also need controlling at the same time
- Water temperatures are getting colder – can slow/reduce mixing
Need technical support?
For any questions or technical support, please get in touch with Stuart below – he’ll be happy to help.
You can also find out more about Kantor by downloading our Kantor handbook here.
Kantor is available to purchase from Agrii in the UK.
