Avid gardeners in the Far North are “majorly concerned” an invasive pest is wreaking havoc with their vegetable gardens and native plants.

Oakura resident Nena Rogers said tropical armyworm has been rampant around the Whangaruru area, north of Helena Bay, over the last couple of years.

Rogers, who owns the Oakura Bay Store and has an extensive home garden, said there is little to no information about the pest “so the caterpillars are travelling faster than bad news”.

Nests have been seen at Whangaruru School, on cars travelling to and from Tuparehuia, and on washing lines and buildings, she said.

“We are majorly concerned about the horror of having all our newly planted autumn seedlings and winter tomatoes eaten and diseased by tropical armyworm caterpillars,” she said.

“It’s not just corn and maize, it’s everything; brassicas, peas, tomatoes, my kaka beak and kowhai.

“It’s now spread right throughout our area.

“People have got no vegetables in their gardens over here because this armyworm has taken over.”

Tropical armyworm is now established in Northland and Auckland according to Landcare Research.

Moist, humid and warmer-than-average temperatures can lead to outbreaks with high numbers of armyworm caterpillars consuming large quantities of pasture and maize crops. They also thrive on vegetable crops.

Fall armyworm is another pest that can feed on over 350 plant species, preferring grasses and cereals, especially sweetcorn and maize.

Fall armyworm was detected in New Zealand in February 2022 after being carried on storm fronts from Australia.

Rogers said she first noticed tropical armyworm at the end of summer last year.

This year they’ve again been infested with tropical armyworm along with some fall armyworm, she said.

Freshly hatched caterpillars have been dropping on heads and clothing, and even through insect mesh, while larger caterpillars are “wiping out whole seedlings then burrowing under soil as a brown grub to later hatch as the armyworm moth”.

Rogers said it’s a “huge problem” for the tomatoes, capsicum, rhubarb, passionfruit and beans she grows, along with her herb garden and green tea plants.

“Everything has been affected.

“We have to find a way to manage it together and prevent the worst-case scenario of all our growers having their hard work destroyed now and every year from now on.”

Biosecurity New Zealand’s director of readiness and response, John Walsh, said tropical armyworm, along with cosmopolitan armyworm and corn earworm, “have been in New Zealand for decades”.

From April 2022 the organisation and sector partners ran a biosecurity response to limit the spread of fall armyworm and try to eradicate it from New Zealand.

“By April 2023, it became clear that fall armyworm was widespread, particularly in the North Island, and that eradication was unlikely because it had been windblown from Australia, and this is likely to repeatedly occur,” Walsh said.

Last December, farmers contacted the Northern Advocate because fall armyworm was “annihilating” their maize crops, hiking the cost of growing the essential feed while also producing devastatingly low yields.

Awanui dairy farmer Leah Frieling, one of many Far North farmers who were affected, said at the time farmers had received “limited guidance” from MPI about what to do.

Frieling recently spotted a few dead moths in her cut maize paddock, and after investigating, found “tropical armyworm is out in full force”.

“It’s been eating all my clover. Clover is a valuable plant, it’s nutritious for cows.

“It’s definitely present and causing damage right now.”

Walsh said though it’s no longer required to report findings to Biosecurity NZ, it was important that farmers and growers continue to report signs of fall armyworm to their crop manager or industry body.

“This will help build a picture of where this pest is and help with the development of ongoing long-term management.

“They will provide specific advice on the best management options for specific situations.

“For home gardeners and lifestyle block owners, if you think you have fall armyworm in your vegetable garden or elsewhere on your property, talk to your local gardening supplier for advice on managing pest caterpillars and moths.”