West: Challenging conditions for pre-em herbicides

Once again rainfall across the region has been very variable, with some areas receiving heavy showers but most still being excessively dry for the time of year. In many later-drilled wheat crops germination is patchy, with seed sitting in dry soil. On the plus side, so far there is no sign of blue mould on the seed and all we need is a few millimetres of rain to boost establishment. 

Soil conditions are challenging for pre-emergence herbicides, especially on the earlier drillings, with blackgrass reaching the three-leaf stage apparently unharmed. It means that follow-up, post-emergence treatments will be applied earlier than usual and we shall have to hope that all blackgrass has emerged by then.

If pre-emergence treatments are having little effect on the weeds, it makes it even more important to carry out the post-emergence follow-up in the autumn, rather than waiting until spring, when the blackgrass will be enormous.

Aphids can be found in many cereal crops and it is time for BYDV treatments. Deter seed dressing will give protection for around nine weeks so most treated crops will not yet need a follow-up aphicide.

One bonus of dry soil is that slug damage is fairly minimal this year but keep checking crops, especially if rain arrives as forecast.

Oilseed rape is now growing strongly. Almost too strongly in some cases so that a growth regulator will be needed soon to hold down some very leggy crops.

So far I have seen little phoma. This may be due to the high disease resistance of the varieties concerned, aided by the dry weather.

The soil is still too warm and too dry for application of propyzamide; it will probably have to wait until November for colder, wetter soil and for crop leaves to die back so that the herbicide can reach the ground. Charlock is flowering in many rape fields and will be treated with bifenox once the crop has been hardened-off by colder weather.

Where beans are being planted, remember to apply a pre-emergence herbicide. Once they have emerged, herbicide choice is very limited.