Importance of varietal resistance in Phoma stem canker control

Last autumn Phoma stem canker escalated within a matter of days and some oilseed rape growers were caught unawares. With the current weather events already encouraging disease development plus high levels of inoculum in stubble, this years rape crop could also be at high risk early on. Growing an oilseed rape variety that performs well and has inherently strong disease resistance is a sensible management approach this year as it gives growers more flexibility in spray timing.

Phoma stem canker can erode yields by at least 0.5 t/ha, which is worth a lot of money these days. In particular if the disease gets hold in a small crop, it can cause even more significant damage, including death of the crop. Last autumn, despite careful crop monitoring, the disease came in very rapidly and some crops were left exposed. Already we have had the necessary 20 days of rainfall after the 1st of August to trigger this disease and there are many susceptible varieties. These susceptible varieties will need two protectant autumn fungicides when the disease gets moving, with the first one potentially clashing with wheat drilling, says Neil Groom, Technical Director of Grainseed Ltd.

Varieties, such as Es Astrid and Es Cubic both of which have excellent disease ratings against Phoma of 7, are easier and cheaper to manage, with the need for fungicide reduced. Resistant varieties appear to withstand the disease for longer, allowing greater timing flexibility of your fungicide, he points out.

Using varieties with high disease ratings together with a comprehensive fungicide programme is a practise which is widely employed in cereals. With high disease pressure combined with the positive economics of rape growing, such an integrated approach makes a lot of sense in oilseed rape, too, says Neil.

Both the low biomass varieties Astrid and Cubic have high Phoma disease resistance ratings of 7. The basis of this resistance to Phoma is multigenic and so is long lasting, reports Neil Groom.

For further information on the oilseed rape varieties Es Astrid, Es Cubic or other Grainseed varieties, please contact Neil Groom, Technical Director of Grainseed Ltd on 01379 871073 or 07774 720240.