Fall armyworm is continuing to spread across North Island maize crops with 15 new findings over the past week, bringing the total number of finds across New Zealand to 45.
The insect pest is thought to have been carried on storm fronts from Australia and arrived in New Zealand in around February 2022.
Foundation for Arable Research (FAR) general manager of business operations Ivan Lawrie said most of the finds so far have been larvae feeding on maize crops.
Primary sector groups with government support have installed 200 traps on farms in the affected area to capture the insect in its moth stage, he said.
“We have had a few moth detections so far but mostly what we observed in the lead-up to Christmas was direct damage from caterpillars in paddocks.”
This leads him to believe that the insect survived the winter due to mild weather conditions, something backed up by modelling.
Insects at the moth stage will be travelling south, seeking warmer temperatures as they move down the country.
“The earlier sown maize crops will have a certain degree of escape because as the season progresses and the crop outgrows the presence of the pest you have less of a chance of getting severe economic damage,” Lawrie said.
He said there is concern that the wet conditions in the upper North Island and subsequent delay in maize being sown this season mean the early development stages of the crop could be at higher risk from the insect.
One positive development is the approval of the insecticide spinetoram, known commercially as SpartaR, which can be used to control fall armyworm.
There are also promising signs that a native parasitic wasp is attacking fall armyworm.
While research into this is still in its early stages, it could mean a degree of natural control available to farmers in the near future, he said.
The worm has been found in all of the areas where it occurred last season, including Northland, Waikato, Bay of Plenty and Taranaki. Lawrie said FAR is processing reports from other regions it is suspected the insect has reached.
“Going forward now, the main thing is to continue reporting. We will continue to collect the data from the moths from the traps but we need growers to be walking their fields and finding any signs of damage and reporting any finds to the MPI.”
This helps FAR build a better picture for modelling and understanding the insect.
“There is no downside for a grower to report any finding, only an upside. There’s no chance of the crop being destroyed or notices being put on paddocks. There should be no fear in reporting a new find,” Lawrie said.