Australia
December 8, 2014

Etiella larvae (Etiella behrii) have infested an estimated 50 percent of mungbean pods in a crop in the Moree region, raising concern this season’s crops will return smaller yields leading into harvest.

Outbreaks of varying intensity have been widely reported in other crops from the Liverpool Plains to the Goondiwindi region to the Darling Downs.

Commonly known as lucerne seed web moth, etiella larvae normally attack pods but in recent years early infestations have attacked mungbean and soybean buds and flowers and have tunnelled into plant stems.

The Grains Research and Development Corporation (GRDC) is advising mungbean growers to be on the lookout for the distinctive moth, for elliptical shaped eggs on pods, flowers and under bracts, and for damaged buds and pods.

Hugh Brier, senior entomologist from the Department of Agriculture, Fisheries and Forestry (DAFF) Kingaroy, said the larvae leave a near-invisible entry hole into pods making them very difficult to detect.

“The larvae are a pale cream or orange colour when they’re young whilst larger larvae are cream or green with pink stipes, but when the larvae are nearing pupation they are often tinged in a pink hue,” Mr Brier said.

The GRDC is requesting growers with infected crops to report and, where possible, send damage samples and larvae to the Integrated Pest Management (IPM) program for assessment.

“Crops with adequate moisture will compensate for low to moderate levels of early damage but major early damage will most likely reduce mungbean yield,” Mr Brier said.
 
“However monitoring of soybean crops last summer suggests soybeans are better able to compensate for early etiella damage.

In soybeans, each larvae consumes only one (1) seed equating to a yield loss of 0.2g per larvae or only 2kg/ha for every larvae per square metre. 

“In contrast, it is likely each etiella will consume as many as four to five mungbean seeds, as they are much smaller than the 0.2 gram soybean seed."

Trials last season found etiella larvae were very difficult to manage once they were established in the pod, making it crucial for growers to detect the pest early.

“Assessments of damaged samples from infested mungbean crops are currently underway and will enable researchers to measure the impact of etiella damage on mungbean seed quality and establish threshold guidelines for future seasons,” Mr Brier said. 

Caterpillar insecticides already registered against helicoverpa in mungbeans and soybeans will also be evaluated against etiella this summer.

Anyone with suspected etiella damage should Hugh Brier on (07) 4160 0740 or 0428 188 069 or email hugh.brier@daff.qld.gov.au

Website: http://www.grdc.com.au

Published: December 8, 2014