Jo Drummond, FAR
New Zealand cereal growers hold world records for both wheat and barley production, however, these records and our recent yield increases are reliant on chemistry to manage weeds, pests and diseases. Looking to the future, climate change, agrichemical resistance and market access issues mean it is unlikely we will be able to be entirely reliant on chemical use in the future.
Agrichemical resistance mutations can develop quickly, while others build up slowly over several years. In the case of strobilurins for Septoria tritici blotch (STB) control in wheat, a single site mutation removed an entire mode of action in a relatively short amount of time, and now, data from Europe has identified STB mutations with reduced sensitivity to SDHI fungicides. In barley, Ramularia is already resistant to strobilurins and recent testing of Ramularia isolates has found 96% are resistant to SDHIs.
Climate change may lead to changes in the spectrum of weeds, pests and diseases we face. For example, increasing temperatures may result in increasing numbers of cereal aphids and stored grain insects. Understanding these issues and considering alternative approaches will be important, especially with synthetic pyrethroids, neonicotinoids and organophosphates subject to review on the EPA priority chemicals
list or already banned overseas.
Resistance and review are also on the horizon for many herbicides. Our challenge is not only targeting weeds but maintaining the few tools we have by understanding how, what and when we are applying them.
So what are the future options? The time has come to consider an integrated approach to weed, pest and disease management. We can use our knowledge of sowing dates, irrigation use, cultivar resistance, the types of pests, weeds and diseases we’re likely to encounter and their lifecycles. We can manage our soils, crop residues and green bridges, monitor our insect populations, encourage beneficial insect predators and strategically use chemistry with best management practices…and that’s probably just the beginning!