Problems are being reported in a number of recently sown brassica catch crops. Some crops appear to have germinated, but areas within the crop are subsequently failing to grow, or even dying. In some instances almost the whole crop has failed in the late establishment phase.

In most reports to date, these problems are occurring in spring barley. The plants began to show symptoms as the first or second pair of true leaves appeared. This is the stage at which plants begin to take up nutrients from the soil, as all growth before that is fuelled from the seed reserves.

The cause>

It seems that all crops showing this problem were sown following some version of shallow min-till establishment technique. A few weeks ago I suggested that there could be a significant risk of herbicide remaining in the soil due to the unusually dry summer and the late application, followed by late planting. At this point it would seem that this is the most likely cause of these problems, as there are signs of herbicide damage before the plants die.

If this is happening, there is little that one can do after the crop is drilled. One of the few things that one could have done would have been to plough, or at least cultivate deep, to help significantly dilute the herbicide residue in the upper seedbed.

Perhaps the most likely offender might be sulfonylureas applied in the herbicide mix. However, there are also signs of problems where hormonal herbicides were applied just ahead of planting. We have seen such problems occur in the past, when susceptible crops were planted following the application of straight hormonal herbicides ahead of planting to kill off volunteers.

That said, the greater risk in most fields must be in situations where SUs were used in the cereal crop. At this point we might hope that recent rainfall and moisture will help to degrade any remaining residual herbicide that may be active in the soil.