CANOLA growers are advised to keep an eye out for diamondback moth, especially if conditions in the coming weeks are dry and temperatures are above average.
SARDI entomologist Greg Baker said growers should monitor crops using a sweep-net at fortnightly intervals throughout flowering to windrowing/harvest.
Mr Baker says sweep-netting at the first sign of damage and at intervals throughout the growing season from mid-July through to late spring is recommended.
“Effective sweep-net monitoring involves taking a minimum of five sets of 10 sweeps in several representative parts of the crop and calculating the average number of the larvae (caterpillars) per 10 sweeps,” he said.
“Record the number of DBM larvae, the numbers of larvae of other moth pests and the numbers of DBM natural enemies. Trends in these regular counts can be a good predictor of the effectiveness of natural enemies and/or the imminent need to spray.”
Entomologist Paul Umina, from cesar and the University of Melbourne, said monitoring DBM populations was an important aspect of an overall integrated pest management strategy, aimed at reducing the risk of DBM developing resistance to available chemistries.
“Knowing what levels of infestation growers have in their canola crops will help them determine whether they need to spray,” he said.
“If DBM economic threshold levels aren’t reached, refraining from spraying is advised.”
DBM has a high propensity to develop resistance and there are more than 80 insecticide compounds recorded globally to which DBM has developed resistance. Because of the high dispersal capacity of DBM moths, resistant individuals can soon dominate a landscape if there is widespread use of the same insecticide group.
SARDI screening of DBM in canola and vegetable production regions indicates that resistance to pyrethroids and organophosphates is widespread. Low to moderate levels of resistance to avermectins is also common.
Mr Baker and Dr Umina were involved in development of the GRDC’s new Resistance Management Strategy for Diamondback Moth in Australian Canola, which aims to minimise the selection pressure for resistance to the same chemical groups across consecutive generations of DBM.
This strategy was developed by the National Insecticide Resistance Management working group of the Grains Pest Advisory Committee, and endorsed by CropLife Australia.
- Details: grdc.com.au