How to deal with resistant rye – NFUonline

Italian rye grass (Lolium multiflorum) is one of the major herbicide-resistant grasses in the UK. As challenges increase during the fall months, it is important to consider an integrated weed management strategy, in order to most effectively control and minimize its impact on crops. When resistance was first recorded in the UK in 1990 and by 2013, evidence showed almost 500 cases of resistance in 33 counties.

Growing resistance

Surveys in 2019 and 2021 indicated that this trend is continuing and that herbicide resistance in Italian rye grass is increasing. The areas most at risk are those where production is mixed, including livestock, arable land and grass seeds. Rye grasses are introduced via three main routes:

  • Seeds plowed into animal dung from grazing
  • Use field-fed hay/silage from farm manure or
  • The slurry in arable rotation seeds returns to the soil from rye grass seed crops.

Rye grass infestation causes significant yield challenges, especially in winter wheat and winter oilseeds. Due to the leaf shape, rye grasses are less conspicuous and therefore easier to overlook, especially in the early stages of development and located within crop rows. Rye weeds can cause significant productivity losses because they compete with the crop for resources.

Italian rye grass processing

While herbicide resistance in Italian rye grass is not currently as widespread as resistance to blackgrass or wild oats, it causes significant challenges when it does occur, meaning that an integrated weed control strategy is the most effective and beneficial approach.

Simple measures, such as ensuring good farm hygiene by thoroughly cleaning equipment, can effectively limit the spread of Italian rye grass seeds by reducing movement between fields and farms. Tillage can also be a valuable management tool, as seeds are unable to germinate at depth.

By understanding weed biology, better decisions can be made regarding its management and control strategies can be tailored to individual farm conditions, thus increasing its success. Where possible, late autumn drilling can also improve Italian rye weed control, taking advantage of lack of seed dormancy.

When herbicides are used as part of an integrated weed management strategy, the use of different active ingredients and a considered approach to timing of applications will contribute to effective weed control.

A successful control program in the fall will also help reduce the chance of secondary peaks appearing in the spring. Rye grasses can germinate over a long period in the fall, so the use of an herbicide treatment with residual activity can be beneficial to ensure continued effects on seedlings that emerge later in the year.

Use of herbicides

Contact herbicides may be more effective if a large number of seedlings have already emerged at the time of treatment, for example if treatment is later in the year. This highlights the importance of thoughtful and appropriate herbicide selection and treatment, based on the specific situation. It is also important to monitor weeds after using herbicides to ensure they are effective.

If resistance is suspected, it is possible to test the seed, which is valuable for informing the ongoing weed management plan, as well as for providing data to inform UK-wide resistance status.

Find out more about the responsible use of pesticides

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