Armyworm on the march in Queensland

Darling Downs grain growers have been placed on alert for bands of dayfeeding armyworms that are on the march, defoliating sorghum, corn and millet crops and threatening yield potential.

While reports suggest that the damage has been patchy so far, the Grains Research and Development Corporation (GRDC) warns that any outbreaks have the potential to cause significant yield loss if crops are defoliated before reaching physiological maturity.

At this time of year, high num­bers of com­mon army­worm and dayfeed­ing army­worm can defo­li­ate seedling crops, sum­mer crops that are still green as well as pas­ture.

The com­mon army­worm is the same species of army­worm that causes dam­age to win­ter cere­als in spring and Department of Agriculture, Fisheries and Forestry (DAFF) Principal Entomologist Dr Melina Miles believes that the high num­bers now may be a car­ry­over from the out­break in north­ern NSW last spring.

“Army­worm out­breaks like these tend to last only one to two gen­er­a­tions as dis­ease, pre­da­tion and par­a­sitism have an impact on sur­vival,” Dr Miles said.

“The threat to win­ter crops is expected to be low, but mon­i­tor­ing as the crops emerge, par­tic­u­larly in prox­im­ity to army­worm out­breaks now, is recommended.

“Both the com­mon and dayfeed­ing army­worm lar­vae look sim­i­lar to Heli­cov­erpa lar­vae. Cor­rect iden­ti­fi­ca­tion is impor­tant because army­worm can­not be con­trolled with Nuclear Polyhedrosis Virus (NPV), and heli­cov­erpa have resis­tance to syn­thetic pyrethroids - the two most com­monly used con­trol options for these species.” 

Dr Miles said control of dayfeed­ing army­worm in crops required good coverage to ensure contact with caterpillars, par­tic­u­larly in crops with thick canopies.

“If treat­ing pas­tures beware of the long with­hold­ing peri­ods for cat­tle grazed on this pas­ture with ref­er­ence to export slaugh­ter inter­vals and export graz­ing inter­vals. These inter­vals are not always marked on insec­ti­cide labels,” she said.

Con­trol options can be found on http://services.apvma.gov.au/PubcrisWebClient/welcome.do.

For identification of common armyworm refer to http://thebeatsheet.com.au/armyworm/avenge-of-the-caterpillars%e2%80%a6/ or pic.twitter.com/T9ZVw4nLTF. For more information visit The Beatsheet at http://thebeatsheet.com.au/armyworm/armyworms-defoliating-sorghum-millet-and-corn-on-the-downs/.

Contact Details 

Elise McKinna, DAFF Media & Communication Officer
07 3087 8576
elise.mckinna@daff.qld.gov.au

Region North