Fall armyworm found in North Canterbury

The fall armyworm stripping a bean leaf. Photo /supplied

The worst fears of arable growers were confirmed with the first outbreak of fall armyworm in North Canterbury.

The discovery came as little surprise, but, unexpectedly the infestation was traced to a sweetcorn crop at an unspecified site instead of maize plantings.

Growers had been bracing themselves for the inevitable with the maize pest already traced in the neighbouring West Coast, initially on a Hokitika farm, and Takaka.

A false scare in a Central Otago paddock has since been ruled out.

While the North Canterbury larvae population is low and at an early stage of development, Foundation for Arable Research (Far) says its presence means crop losses could be significant when combined with a large corn earworm population.

Heavy damage and an accumulation of caterpillar faeces on a maize crop near Hokitika from a fall armyworm infestation. Photo / Supplied / Far

The discovery brought the total number of fall armyworm finds this season to more than 130.

Of some consolation to maize growers is the availability now of insecticide Sparta for both aerial and ground spraying on maize and sweetcorn crops.

Growers are being advised to consult advisers before beginning this control and avoid insecticides that are ineffective for removing fall armyworms and potentially harmful to beneficial insects.

Far says many crops are close to the harvest stage around the country, which means the fall armyworms’ preferred food source will be reduced.

The foundation says it is important for growers to scour neighbouring paddocks, as they could look to other crops for a food source in the absence of maize and sweetcorn.

There continue to be reports of fall armyworm larvae being attacked by a parasitic wasp which will help contain numbers.

Australian guidelines suggest that economic losses occur in maize crops at the whorl stage and onwards when at least 20 per cent of plants have larvae present and there is 75 per cent damage to them.