Growers Urged To Check For Maize Pest

• Published date: 08 March 2023
• Publication title: West Coast Farming Times, The

The origin of the West Coast fall armyworm (FAW) infestation - the only confirmed South Island detection to date - may never be known

The level of larvae development in the first West Coast FAW site to be identified meant it had been there for at least 50 days before its mid-January find, says Foundation for Arable Research general manager of business operations Ivan Lawrie.

"So, it was two months in the making before it was detected."

Scientists have not been able to confirm whether the infestation had overwintered or was blown over from Australia in a separate incursion to the one found in the North Island last year.

"We don't know where the moths came from - whether they flew down from the North Island or from Australia, as we had no early detection. In Northland, there was earlier detection of the larvae, which would indicate it overwintered."

Adult FAW moths are strong flyers and can travel hundreds of kilometres on storm fronts.

To date, FAW has been confirmed on 12 West Coast properties this season, ranging from Hari Hari in the south up to the Reefton area. The West Coast has frost-free pockets and a mild season this year may have supported growth of the pest.

Nationally, FAW has been confirmed on about 115 properties this season, with varying degrees of damage. FAW was first detected in New Zealand in March last year, likely windblown from Australia.

In the North Island, the main regions aff ected continue to be the big maize growing areas of Northland, Waikato and Auckland, with a scattering of finds in Taranaki and the eastern North Island.

"Early evidence would suggest FAW can live in parts of New Zealand all year round, so crop scouting, especially in the early stages, is essential to keep populations under control," Mr Lawrie says.

For serious economic damage to occur, more than one or two generations of FAW are required on a crop to build up numbers. "In Northland, we have started the third generation and that is when numbers of larvae grow exponentially.

"So, the later the crop, the more vulnerable it is.

"Modellers suggest that there should be only three generations doing active damage in New Zealand and probably one more in Northland.

"We encourage industry reps as well as growers to actively check crops for any sign of damage, or infestation, acknowledging that it is much more difficult to do this in the advanced stages of the crop," Ivan Lawrie says.

FAW may be able to overwinter in milder regions but it can't survive prolonged low...