Authorities and farmers are keeping a close eye on grass crops after the discovery of a small amount of blackgrass in Mid Canterbury. The plant has been found on three properties in small quantities.
David Yard, senior response manager with the Ministry for Primary Industries, said it appeared blackgrass might not be as invasive in New Zealand as in Europe.
In Europe the plant has proved resistant to herbicides but Mr Yard said it appeared it was more readily controlled by sprays in New Zealand. New Zealand farming methods may also help to control the grass.
One plant was found on one property, 30 on another and between 100 and 200 onthe third.
The farms were among 24 properties under surveillance after the discovery of three blackgrass seeds in a ryegrass produced in Mid Canterbury in 2015 and 2016. The seeds were identified from representative samples taken from a 63-tonne consignment destined for export.
‘‘We suspect it came from a consignment of seed imported from England in 2007,’’ he said.
That seed was traced to the 24 properties under surveillance, all of which are in Mid Canterbury.
At the time the suspected contaminated consignment was imported, blackgrass was not regulated, Mr Yard said.
The latest discovery was found on the three properties in very low levels, he said.
‘‘We couldn’t find any more on other farms.’’
Most of the plants found had been destroyed, but a small number had been kept for herbicide testing, he said.
‘‘The key message is vigilance, both with velvetleaf and blackgrass. That’s better done by the farmer.’’
Guy Wigley, Federated Farmers biosecurity spokesman and national arable chairman, also believes that blackgrass can be eradicated.
New Zealand had three things going for it which English farming systems did not — burning, which was recognised as a good control, ploughing and a grazing regime, he said.
‘‘It is vital to retain that tool [burning]. Blackgrass doesn’t like being ploughed and it doesn’t like being grazed. Those three things are on our side.
‘‘All importers need to play their part when sourcing material and get it from areas where such pests are not endemic.
‘‘Way back then it wasn’t recognised as a problem weed. Since then it has become a problem in England. They have lost some of their tools for dealing with it and it has a resistance to chemicals.’’
He applauded MPI for its effort in tracing and monitoring potentially affected properties.
Federated Farmers said if blackgrass was to establish in New Zealand it would have serious economic and environmental impacts on grain and seed crop production through reduced crop yields
The impact of blackgrass on the arable industry through reduced yields was estimated to be between $8.14 million and $82.4 million, without including any herbicide and machinery costs, it said.
Anyone who suspected they might have blackgrass should contact the MPI pests and diseases hotline, 0800-809-966.
Blackgrass (Alopecurus myosuroides) is a small-seeded and narrow-leaved annual grass weed that can grow up to a metre high.
It can germinate in either autumn or spring, but experience from the northern hemisphere suggests that autumn germination ismuch more common (more than 80%).
Blackgrass populations appear to persist longer in wet soils. In favourable conditions, seeds can survive for up to two to three years but a small percentage may survive for a longer period.
Blackgrass seed heads can easily be mistaken for other common grass weeds. In particular they are very similar to Timothy, meadow foxtail, Phalaris aquatica and sweet vernal.
Mature plants are easier to distinguish as their reddish purple seed heads emerge. Plants typically produce five to 12 seed heads and each seed head can produce up to 100 seeds.