FAR’s Mike Parker, head of the MPI SFF funded Avoiding Glyphosate Resistance project says New Zealand is one of only two countries in the world, the other being Argentina, where both Lolium multiflorum (annual or Italian ryegrass) and Lolium perenne (perennial ryegrass) have developed resistance to this commonly used herbicide.
 
Mr Parker says confirmation that both species are resistant is of concern, but he is pleased that due to growers coming forward we have an opportunity to research solutions for the wine industry which will be acceptable to our overseas markets.
 
“It is important that anyone who suspects that they have glyphosate resistant plants on their property doesn’t turn a blind eye. We recommend re-spraying plants which survive a glyphosate treatment and recording the rates of glyphosate used. This will rule out the possibility that the plant survived because it didn’t get good spray coverage.  If plants survive a second spray, contact the project team for further information on how to submit samples for laboratory testing.”
 
Mr Parker says the level of resistance being exhibited by some populations is also of concern.
 
“Initially it was thought that resistance might be 2-4 fold (plants require two to four times the recommended rate of glyphosate to kill them), but the actual level has now been shown to be 10-30 fold.”
The Avoiding Glyphosate Resistance group is working at several levels to understand how, where and why glyphosate resistance is occurring in New Zealand, and also to develop a strategy to prevent the situation spreading to other regions, and other plants.
 
The mechanisms of glyphosate resistance are complex and vary from species to species. Currently testing for resistance is a long time consuming process.
 
A Massey University team led by Dr Kerry Harrington is developing a ‘quick test’ for glyphosate resistance, with the aim of reducing the amount of time it take to diagnose a resistant plant from three months to a week or less. Dr Harrington says one method is looking very promising, but more work is required to ensure it is accurate.
 
“A quick and easy DIY test would make it much simpler and faster for growers to find out whether a suspect plant is resistant or not.”
 
The group is also developing an awareness campaign, as surveys have shown that many people are still unaware of the factors that lead to glyphosate resistance, and how it can be avoided. Mr Parker says the best advice they can give at this stage, is based on standard pesticide resistance avoidance strategies: don’t repeatedly treat one area with a product from the same chemical family, or if appropriate, apply a mixture with a chemical from another mode of action family.
 
Mr Parker says a number of weed species which have developed glyphosate resistance in other countries, should also be of concern to New Zealand farmers. These include fleabane species, amaranthus species, ryegrass species and summer grasses.

Any farmer suspecting glyphosate resistance, for their sake and that of other farmers, kindly contact Mike Parker (021 960078) or Dr Trevor James (021 0458305).