YOUR LEVY AT WORK
A BIOSECURITY THREAT MARCHES CLOSER Words by Anna Rathé : Biosecurity Manager, HortNZ
Photo by Mr Noy Sopha, as part of NZAID project in Cambodia, Plant & Food Research
Situation update In April last year I wrote an article in this magazine on an emerging biosecurity threat – the fall armyworm (Spodoptera frugiperda) which had recently made landfall in the north of Australia for the first time. Since then, fall armyworm has marched its way south through mainland Australia. After the first detection on two Torres Strait Islands in January 2020 it turned up in Queensland in February 2020, The Northern Territory and Western Australia in March 2020, New South Wales in September 2020 and there have recently been sightings in Victoria. In December 2020 there was a preliminary report of larvae from a single field in New Caledonia. Fall armyworm has proven itself a highly successful invader. It has made its way to over 60 new countries, none of which have managed to eradicate it. It is clear that this pest is moving progressively closer to New Zealand, and we need all growers to keep an eye out. If it were to arrive on our shores, early detection provides the best chance of managing the pest.
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NZGROWER : APRIL 2021
What to look out for Eggs
Dome-shaped cream-coloured eggs are laid on the underside of leaves near the base of the plant. Usually, eggs are laid in clusters of a few hundred which the adult moth covers in a layer of greyish furry scales.
Caterpillars
Caterpillars go through six larval instars. As they develop the larvae grow in size, starting at around 1.5mm and reaching up to 34mm when mature. The instars change in colour from greenish, through to orange and then brown. Fall armyworm caterpillars tend to hide during the day in the whorl or leaf axils. Crop damage is most likely to be observed during the summer and early autumn months when larvae are feeding.
Adults
Adult moths emerge at night and are highly mobile. The moths have a mottled grey/brown forewing, a white hindwing and a wingspan of 30–40mm.
