The find could jeopardise herbage seed exports and long term, if black-grass became established here, hike cropping farmers’ costs.
However, the industry and the Primary Industries Ministry hoped it was a one-off and contained.
An MPI pre-export inspection found three seeds of the pernicious annual grass in samples of a 63t consignment of ryegrass cultivar Nui, which was grown near Hinds in mid Canterbury.
Of seven lines, five 10t lines were clean but a 10t line and the remainder 3t line were contaminated, MPI’s Brad Chandler told Farmers Weekly.
One of the clean 10t lines had been exported but the other lines and the paddocks where the crop was grown had been secured by Assure Quality staff.
Straw from the seed crop, which was baled and removed, had also been traced and put under movement control.
Offal from cleaning the seed crop had been “accounted for,” according to an MPI advisory notice to the seed industry.
Subsequent visual inspections of the paddocks where the seed was grown didn’t find any black grass plants.
Chandler said how the paddocks would be managed in future had yet to be determined.
“MPI and industry are working together to trace the source, including the imported Nui seedlines used in the paddock.”
The crop that produced the contaminated seed was sown in 2015 so the contaminated seed was the first harvested off the paddock.
Federated Farmers’ grain and seed chairman Guy Wigley said it was a credit to MPI’s staff and systems that the contamination was detected but the implications of the find were concerning.
“Black grass is widespread in Europe so there shouldn’t be any trade issue there but other countries like New Zealand are black grass-free so for them it could be problematic.”
Chandler said while the trade implications were not in his remit, if NZ could show the incident had been isolated – “and at this stage it looks like it is” – importing countries should accept that NZ remained black grass-free.
“We do our own export tests on all seed lines which is what picked this up.”
Trace-back work on the seed source and tracing forward to determine potential black grass seed distribution continued and an across-industry working group had been formed.
MPI said that while the source of contamination was unclear – Wigley noted that while seed was most likely, machinery imports were another possibility – there appeared to be no connection to the spill of a black grass-contaminated seed line in July 2013 because that was along a route between Ashburton and Methven.
MPI also said it was too early to suggest the contamination was a result of a border failure because black grass seed could have entered NZ before it became a regulated species in June 2007.
Two lines of Nui were used at the affected property and all other properties receiving those lines had been identified and were to be followed up.
Imports of barley and wheat in 2012, 2013 and 2014, of which 450 lines had been identified, were also being looked at as a possible source.
Cropping problem
INDIVIDUAL plants of black grass (alopecurusmyosuroides) are not that competitive with a cereal crop but each plant can shed thousands of seeds so over a few seasons populations build to the point where near total yield loss can occur.
With such high populations herbicides have to be highly effective but the weed has become resistant to many, forcing repeat applications and multiple mixtures.
In extreme cases United Kingdom growers have been forced to avoid growing cereals on infested paddocks for several seasons and many more suffered substantial yield losses despite their best efforts to control the weed.
It has not become a problem in pasture in Europe.
