West: High phoma levels in oilseed rape

It’s the middle of February and just when things were looking good for the start of spring drilling, 15mm of rain over the weekend has probably put a stop to field work for a few days. That’s annoying, but with less than 150mm of precipitation from rain and snow (Vale of Severn figures) since the start of October, we do need the rain.

Beans and barley will be drilled at the next opportunity and both crops will need pre-emergence herbicides for grass and broad-leaved weeds. Choice of product will depend upon the weed spectrum expected. There are few options for post-emergence grass weed control in spring barley and even fewer for broad-leaved weeds in beans, once the crop has emerged.

Oilseed rape crops have, on the whole, come through the winter very well. However, there are high phoma infestation levels, particularly on varieties with low resistance. As there are also reports of light leaf spot beginning to develop, an early fungicide is advisable, applied as soon as possible. There is no need for any growth regulation at this stage so a flusilazole product would be the preferred option.

For broad spectrum weed control, carbetamide can be applied in oilseed rape up to the end of February.

It is worth checking oilseed rape crops for charlock, cleavers and overwintered or newly emerging grassweeds. Mature charlock has been killed by the frost but smaller plants have survived. They can be controlled to some extent with bifenox. Check that the crop leaves are well waxed and that the crop is not under stress before spraying, as it can be a harsh product. Cleavers can be suppressed with Galera (clopyralid + picloram) once the weeds are actively growing.

Spring germinating brome and blackgrass, which are now at the one leaf stage, can be controlled with contact graminicides.

Cereal crops have developed well, despite the winter weather. There are the usual infestations of septoria in wheat and rhynchosporium and net blotch in barley but it is too early to treat these.

With recent mild weather it is just about warm enough for applications of Atlantis (iodosulfuron + mesosulfuron) but beware that a return to lower temperatures is forecast and this could stop blackgrass growth.

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