PGRO Crop Update (04.04.13)

jimScrimshawSPRING-SOWN PULSES CAN HELP TO BEAT THE BLACKGRASS THREAT

“Spring cropping with pulses can help to fight the ever-increasing problems from blackgrass in cereal crops, says PGRO Principal Technical Officer, Jim Scrimshaw. “Increasing incidences of resistance mean that chemical control of blackgrass in cereals is becoming less and less dependable with some products.”

With no new chemistry in the pipeline, strategies that involve the ‘stacking’ and ‘sequencing’ of existing products along with cultural techniques should be considered together to keep on top of the problem.

The majority of blackgrass seed germinates from the upper few centimetres of soil. If there has been a high seed return, then ploughing can bury seed to a depth from which germination is unlikely. This can make a significant contribution to reducing blackgrass numbers.

There is, however, the potential to plough viable seed to the surface. For this reason, historic knowledge of blackgrass distribution and the cultivations used is useful. The current wet conditions, though, are not conducive to using the plough.

A spring crop - such as field beans or combining peas - increases the window of opportunity and, depending on seed dormancy and the season, it may be possible to spray off up to three flushes and dramatically reduce the blackgrass population. Rotations including spring crops can help to reduce grass weed problems in general.

Graminicides such as Laser (cycloxydim) and Aramo (tepraloxydim) are available and can be useful post-emergence in spring pulse crops. Laser can control enhanced metabolism populations, and Aramo also has activity on target site resistant populations. Reduced blackgrass numbers from employing perhaps more cultural techniques when considering spring pulses would hopefully mean effective control from these materials if required.

“Disappointing blackgrass control in cereals may cost over £100/ha. The opportunity to drastically reduce problem blackgrass populations must have some financial worth to the farm business. This is on top of the traditional advantages of pulses - the opportunity to diversify the rotation, spread the work load, acquire free nitrogen and increase yield in the following cereal crop,” adds Mr Scrimshaw.