Attempts to eradicate fall armyworm have moved to a long-term management programme, with farmers urged to remain vigilant.
As it is apparent that fall armyworm is unlikely to be eradicated in New Zealand, the fall armyworm response has ended, a Foundation for Arable Research (FAR) biosecurity report has advised.
An industry-led transition to a long-term management phase is now underway.
As the management phase begins, it is important farmers remain vigilant and keep scouting any maize and neighbouring paddocks.
With the “unwanted organism” status of fall armyworm revoked, it is no longer mandatory to report finds.
“However, significant observations remain important so please record them and inform us,” FAR general manager Ivan Lawrie said.
The life cycle of fall armyworm has begun to slow as temperatures get colder, but Lawrie said it is still important to stay vigilant as fall armyworms will target a large variety of crops.
They have been observed on ryegrass and clover in a harvested maize paddock. Volunteer maize should not be overlooked either.
There is a total of 139 confirmed reports of fall armyworm across NZ.
FAR welcomes any information on new host plants as it begins to understand overwintering capabilities.
Meanwhile, nine velvetleaf plants were found in a Mid Canterbury paddock during routine surveillance this autumn.
The paddock is associated with the 2015 incursion via imported fodder beet seed.
FAR is urging all growers to keep an eye out for this weed as its seed can remain viable in the soil for up to 60 years.
Velvetleaf (Abutilon theophrasti) is originally from China and India and become a problem in many countries, including NZ.
It can decrease crop yields and cause economic damage to agricultural production as it is an aggressive weed that quickly outcompetes crops and other plants for water and nutrients.
Velvetleaf has been present in NZ since 1948, though reports of its distribution had been limited.
More significantly, it was found in 2015-2016 on several farms in the South Island, originating from imported fodder beet seed.
It has since been found in a growing number of properties across the country.
Velvetleaf has the potential to reduce New Zealand’s GDP by up to $484.7 million by 2030.
FAR said all velvetleaf finds since 2015 have been in fodder beet paddocks sown with one of four varieties: Kyros, Bangor, Troya or Feldherr.
These varieties were sold in both the North and South Islands in the 2015-2016 season.
All growers of these fodder beet varieties are advised to continue to check their crops for velvetleaf throughout the growing season.
As the seed is viable for up to 60 years, long-term management is vital as is on-farm biosecurity.
It is still possible that this weed could be present in other fodder beet varieties, so farmers need to keep an eye out on all crops, Lawrie said.
Of ongoing concern is black grass, with FAR calling on all Canterbury farmers to continue looking out for this pest.
Black grass is an unwanted organism with the industry and the government working together to respond to incursions.
Black grass (Alopecurus myosuroides) has become a serious grass weed in winter cereals in the United Kingdom and Europe, where many populations have developed resistance to many of the grass weed herbicides used in winter cereals.
Management of the pest requires an integrated weed management approach using a range of cultural options in conjunction with herbicides.
Since the initial detection of black grass in Mid Canterbury in 2012 – which was successfully contained – there have been isolated detections in NZ related to seed imports.
Farmers finding either of these plant pests should not disturb the seed head but take a photo and call the pest and disease hotline on 0800 80 99 66 to report the suspected find.