Spray early for optimum weed control
Timing of pre-emergence and post-emergence herbicide application needs to be precise to get the best results, writes Ciaran Collins
Pre-emergence and early post-emergence herbicide applications in wheat and barley will give the best weed control this autumn.
In the past, isoproturon (IPU) offered farmers a degree of flexibility in the timing of herbicide applications, but since its use was prohibited in September 2017, farmers need to be more precise with herbicide applications to get satisfactory weed control.
This is particularly relevant for the control of annual meadow grass (AMG) in winter barley where pre-emergence or early post-emergence timings are required to achieve the most reliable control.
Know your target
Knowledge of the weeds that are most likely to occur in a field is key to herbicide selection and timing of application. Good records from previous seasons are an important component of any weed control strategy.
Weeds have different competition patterns so priority will need to be given to weeds that will impact greatest on yield. The table (right) outlines the relative competitiveness of weeds in winter wheat and demonstrates how a severely competitive weed like cleavers would take priority in a herbicide programme over a moderately competitive weed like field pansy. The control of broadleaf weeds will be based on products containing diflufenican (DFF), pendimethalin (Stomp), prosulfocarb (Defy) and picolinafen (Flight) in combination with specific grass weed products.
There are many combinations available on the market but herbicide selection should be based on the expected weeds in combination with early application.
Annual meadow grass (AMG)
When IPU was on the market, AMG could be successfully controlled up to early tillering. The currently available suite of active ingredients can give excellent control of AMG, but success will only come from pre-emergence or early post-emergence applications. Control will be reduced after AMG reaches the two leaf stage. Later, control can be achieved in wheat with Alister Flex in the autumn or Pacifica Plus in the spring.
Successful control of AMG can be achieved with pre-emergence or early post-emergence herbicide applications. These include: