Canterbury escapes pest - for now

Canterbury maize crops have continued to avoid the relentless march of the fall armyworm but growers aren’t holding their breath after a couple of near misses.

A false scare in a Central Otago paddock brought home the risk of future infestations.

Initially, it was thought the insect pest with a voracious appetite for maize and sweetcorn had colonised in the south. Further investigation by the Ministry for Primary Industries revealed the culprit was an early instar larvae of diamond back moth, Plutella xylostella, which is commonly found in brassicas and other broad leaf crops.

The risk remains with infestations found in neighbouring West Coast, initially on a Hokitika farm.

Federated Farmers Arable chairman Colin Hurst said Canterbury growers were just glad it had yet to arrive.

‘‘It’s just something else that will attack mostly the maize crop. There’s been quite a bit more maize going in Canterbury this year and the numbers are certainly up in our [South Canterbury’s Makikihi] district and Waimate and talking to other farmers across other parts of Canterbury as well. We’ve had a warmer season with our changing climate maize will be a growth crop.’’

Mr Hurst said his family put in maize this season for the first time and were amazed how well it had grown during a dry phase as the greenest crop on the property at the moment.

This crop was initially planted for grain, but could be harvested in late March as silage because of strong demand. Otherwise, it will be taken into August for grain harvesting.

He said laboratory updates on additional infestations were put on hold because of flooding from Cyclone Gabrielle.

Hopefully, the insect pests has been washed away, but this was less of a worry because maize crops had been decimated in parts of the North Island, he said.

‘‘We are really feeling for the growers in the North Island. Words can’t describe it. I’m a Federated Farmers board member so I’ve got my colleagues up there on the East Coast dealing with this — it’s pretty tough. Like other growers and the horticultural sector they’re being hammered.’’

Mr Hurst said there needed to be further thought about pine forestry on easily eroded land because of many slips and it probably needed to go back into native forestry.

He said heartening for growers was the application for a chemical treatment to be spread by aircraft and good progress being made with researching other insects to naturally predate on thearmyworm.

‘‘So that’s really positive and there are other applications for other chemicals to be used as well so there’s been quite a bit of effort going on in the background to get some controls in place,’’ Mr Hurst said.

Fall armyworm is thought to have first landed in New Zealand a year ago after being carried on storm fronts across the Tasman Sea.

Initially, it was contained to warmer Northland, Waikato, Bay of Plenty and Taranaki. The discovery of insect infestations by authorities at three sites on the West Coast in the week ending January 13 added the South Island to the list.

Foundation for Arable Research (FAR) is advising Canterbury growers to go through every maize crop with a fine tooth comb.

So far there are no signs of fall armyworm in the province, although crop damage from other moth pests has been discovered during surveillance.

Canterbury has not escaped completely unscathed from other crop pests with two new findings of black grass found last month.

Foundation for Arable Research says both findings are linked to the 2021-22 incursion in flax linseed crops and a response is under way to deal with affected properties. An infected line is understood to have been grown for seed multiplication and other lines are also under surveillance.

Mr Hurst said growers were questioning how it happened and there would be a thorough investigation to provide answers.

‘‘The black grass is something I’m really concerned about that it’s popped up again. As we speak, flax-linseed crops are being cut, baled, wrapped and burned or buried because of the risk of black grass.

"I’m dealing directly with some of the growers and it’s just not good that it’s happened. There’s also a wheat crop that’s going to be destroyed because of black grass in it.’’

He agreed with FAR for Canterbury farmers to continue to keep a sharp lookout for the weed pest as it was important any new finds were reported quickly.

‘‘There’s a little bit of an issue we’ve had seed that’s seeded and it’s probably fallen on the ground so those paddocks will have to be intensely monitored for a number of years.’’

If they believe they have found it, they should not disturb the seed head, but take a photo and call the Pest and Disease Hotline on 0800809-966 to report the suspected find.

Black grass was known to be a serious pest weed in Europe and the UK, as it was resistant to many herbicides, making it difficult to control.

TIM.CRONSHAW @alliedpress.co.nz