Managing herbicide resistance – the end game

Herbicide resistance was first reported in New Zealand in 1979 when fathen (Chenopodium album) survived high rates of atrazine. Since then studies on herbicide resistance have been ad hoc and followed complaints of herbicides failing to control weeds that are normally susceptible. Between 1979 and the commencement of this research programme, ten more species were found to be resistant to one or more herbicides.

The research programme initiated in 2018 with funding from MBIE Endeavour fund and various stakeholders comprised four research areas viz. RA1 Anticipaticipating herbicide resistance, RA2 Changing herbicide practices, RA3 Identifying instances of resistance and RA4 Managing herbicide resistant weeds.

Key findings were: RA1 revealed that herbicide resistance is strongly correlated to agricultural intensification, fertiliser and herbicide use as well as prevalence of a weed, chromosome number and seed mass. From global data, machine learning is able to help predict resistance high-risk weed species.

RA2 found the drivers of grower behaviour re herbicide use, were complex and involved personal preferences as well as farm system and industry requirements. Education on herbicide resistance needs to happen at multiple levels.

RA3 Surveys carried out found much higher levels of herbicide resistance than originally anticipated and identified six new resistant weed species. Discovery of resistance mechanisms lead to the development of genetic quick tests for resistance.

RA4 The development of electro-microshock technology offers a new nonchemical intervention for managing resistance weeds.

Stakeholder feedback revealed that coordinated engagement with farmers destigmatized herbicide resistance, enabling necessary conversations and co-learning to take place.