Controlling Phoma

After a successful autumn season of OSR establishment we have seen weather conditions that have been conducive to disease. Phoma is the main autumn disease in OSR, later sown crops are at the greatest risk. Although the disease presents as a leaf spot in the autumn, the impact is seen more in the summer where stem cankers develop. Stem canker reduces yield by restricting water and nutrient uptake through the stem, resulting in premature senescence in the summer. Susceptible varieties, water temperatures and available moisture are risk factors which will increase the incidence of phoma. There are several phoma forecasts available from the AHDB and Bayer. The autumn symptoms are white circular lesions that become dotted with small black pycnidia see photo above.

Phoma Control

The threshold for treatment is when 10% of the plants are affected by phoma leaf spotting in the autumn. Once this threshold has been reached, we recommend spraying with Septuna (difenconazole) if no growth regulation is desired or Metal (metconazole) if growth regulation is required.

If you want to talk to a BASIS qualified advisor or purchase control products, contact our team today - 01243 784171 or emails chems@bartholomews.co.uk