Preventing a widescale increase in ALS resistant broad-leaved weeds through effective management in cereal/oilseed rape rotation, using common poppy as an indicator species

Abstract

The project aim was to (1) identify and quantify the risks of ALS resistance in broad-leaved weeds, (2) develop the optimum management practices to manage, reduce or eliminate developing resistance, (3) raise awareness of the issue and provide information about the early warning signs and how to manage the situation in the UK. The focus weed was common poppy (Papaver rhoeas) which was used as an indicator species for broad leaved weeds in general.

The key results from both the field and container experiments showed that a non-ALS herbicide programme consistently provided the highest control across all experimental years and poppy populations (both ALS-resistant and susceptible populations). A mixture or programme of non-ALS + ALS herbicides also provided good control. The use of a post-emergent ALS inhibitor herbicide alone was always the weakest treatment with the poorest control of known resistant poppy populations. These results provide further evidence that common poppy populations resistant to ALS inhibitors can be controlled using well-timed applications of other herbicide modes of action.

The number of confirmed herbicide resistant broad-leaved weed populations in the UK is still relatively low compared with grass weeds. This project shows that ALS-resistant broad-leaved weeds are currently controllable with alternative modes of action and a robust herbicide-resistance management strategy is essential. It is crucial that a wide range of effective herbicide alternative modes of action are maintained to enable control of resistant populations and prevent further cases of resistance. Early detection, monitoring and removal of patches of problem broad-leaved weeds will also limit and potentially prevent resistance spread.

The project results provide evidence of the importance of retaining the availability of effective herbicides, by quantifying the value of alternative modes of action in resistance management strategies. Practical guidelines for resistance management strategies for broad-leaved weeds have been provided for agronomists, farmers and regulators, in the form of an AHDB leaflet and through the wide dissemination of results via agronomic events, workshops, national and international scientific conference papers and presentations.