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Canola Growers Urged To Look Out For DBM

22 August 2011

AUSTRALIA - Canola growers should be vigilant and monitor crops for diamondback moths (DBM), which are in unusually high numbers in parts of the northern agricultural region and near Esperance.

This is the message from Department of Agriculture and Food (DAFWA) entomologist Svetlana Micic, who said DBM had damaged early flowering canola buds west of Esperance, potentially affecting yields.

“Growers should monitor their canola crops regularly from when flowering starts, especially if conditions are warm and DBM numbers are building up,” Ms Micic said.

“It is good to see what is going on in the crop and control pests early if necessary, because by the time damage has been done it can be too late.”

Ms Micic said the northern grainbelt and Esperance were DBM ‘hotspots’ this year due to localised summer and autumn rain, and warm conditions during the growing season.

“Other areas of the grainbelt may also have high levels of DBM if there was a ‘green bridge’ over summer and autumn with a lot of self-sown canola or radish present,” she said.

Ms Micic said DBM thresholds for spraying were a guide only and depended on factors including crop maturity; potential returns from the crop; and the costs of chemicals and their application.

“GRDC supported research has shown that if DBM numbers are rising, crops may need at least two sprays, with the thresholds for spraying being about 10 caterpillars in 10 sweeps at the pre-flowering stage; and 50 caterpillars in 10 sweeps at mid-flowering,” she said.

Ms Micic said DBM could cause yield losses of up to 80 per cent in severe outbreaks like those which occurred in WA in 2000 and 2001.

“Damage to crops this year is likely to be sporadic with many grainbelt crops having levels of DBM which will not require control,” she said.

The GRDC has facilitated the submission of an application for an emergency permit to manage insecticide resistant DBM populations, based on data generated through GRDC funded research.

A decision by the Australian Pesticides and Veterinary Medicines Authority (APVMA) is pending.

Ms Micic said WA growers should also watch out for other caterpillar pests including native budworm.

“Native budworm are capable of causing more damage than DBM and appear very similar to DBM when small,” she said.

TheCropSite News Desk

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