Moth pest fall armyworm found in Hamilton, growers asked to watch for pest

Biosecurity New Zealand and primary sector partners are asking maize and corn growers to keep an eye out for the moth pest fall armyworm. Photo / Crop Science Australia, Ted C. Macrae

The moth pest fall armyworm has been discovered at two properties on the outskirts of Hamilton so Biosecurity New Zealand and primary sector partners are asking Waikato maize and corn growers to keep an eye out and report any signs of caterpillars on their plants.

The fall armyworm is a plant pest that can cause damage to crops. It is native to the Americas and can feed on more than 350 plant species, including corn, beans, capsicum, onions, kumara and tomatoes.

The moth's larvae particularly feed on stems and leaves which causes crop damage. They can skeletonise the leaves and severe infestation can cause unwanted defoliation.

On corn, larvae attack the ear, silks, cob and kernels which reduces leaf mass, fruit, pods, seeds and the overall plant health.

Adult moths are between 16 and 18mm long, and have a wingspan of 38mm. The forewings are a brown-grey colour and the hind wings a cream colour.

Larvae change from a green-brown to a brown-black colour as they mature and are almost black in the "armyworm" phase. Eggs are only about 0.4mm and laid on leaf surfaces in masses of between 150 and 200, covered with a protective layer of scales.

The fall armyworm was introduced to Africa, Asia and parts of Australia in 2016, but because it usually thrives in very warm climates, it was thought unlikely the pest would spread into colder climate zones like New Zealand. However, in March this year, egg mass belonging to the moth was found in Tauranga.

The fall armyworm has now been found in Hamilton. Photo / Supplied

The fall armyworm is a hitchhiker pest and work done by Biosecurity New Zealand shows the moth can spread via wind dispersal events from Australia.

It is unable to hibernate over winter, so populations, including eggs, larvae, pupae and adults are likely to die out during the winter period.

If you find suspicious caterpillars please report to the MPI here or you can report via the Find-a-pest app or call Biosecurity New Zealand's pest and disease hotline at 0800 809 966.

Biosecurity New Zealand is asking people to take a clear, top-down photo of the suspicious caterpillar.