Moth de resistance!

Insecticide resistance is a major issue for growers in managing pests.  The Diamondback moth (DBM) is top of the stakes when it comes to out-competing those in the business of keeping pests at bay.

Growers of cruciferous crops are all too familiar with the DBM, also known as cabbage moth or Plutella. DBM has an unrivalled ability to develop resistance to all classes of insecticides and is potentially the most damaging and difficult to manage pest of brassica vegetable crops. The cost of controlling DBM globally is estimated to be between $4 and $5 US billion per year; it is considered the most economically important pest of cruciferous crops in Australia.

Sustainable management of DBM requires the adoption of flexible integrated pest management strategies. As DBM continues to outsmart growers, researchers at the University of Queensland have been conducting research into how the DBM metabolically detoxifies insecticides.   The research was funded by Horticulture Innovation Australia Limited (HIA) from vegetable R&D levies and funds from the Australian Government.

Their findings were released recently – Manipulation of regulatory microRNAs to suppress insecticide resistance in diamondback moth. It’s complex stuff but here are a few key points;

  • the way in which the DBM develops resistance is through metabolic detoxification
  • the project explored the effect of insecticide resistance and insecticide exposure on the microRNA profile of DBM larvae – microRNAs are small ribonucleic acids that play significant roles in various physiological and developmental processes in all plants and animals by regulating expression of genes
  • results showed changes in the microRNA profile of Deltamethrin-resistant and Chlorantraniliprole-exposed DBM larvae
  • results also showed that one of the microRNAs (miR-2b-3p) can significantly enhance mortality in Deltamethrin-resistant DBM larvae; feeding this microRNA to the Deltamethrin-resistant DBM larvae led to increased mortality when the larvae were exposed to the insecticide, i.e., it reduced resistance
  • to move towards a practical application of the findings, researchers are using this information about the microRNA to produce genetically modified plants that contain the microRNA.

In the meantime, the best means of keeping on top of DBM is through flexible and multiple control strategies in keeping with IPM (integrated pest management) and IRM (insecticide resistance management) plans. Key to these are;

  • correct identification of DBM throughout all life cycle stages
  • regular and rigorous crop inspection and monitoring (scouting)
  • early detection
  • recognising weather conditions conducive to DBM reproduction and growth (warm, moist conditions),
  • encouraging natural predators to DBM by minimising the use of broad spectrum insecticides,
  • good farm hygiene such as ploughing in harvested crops
  • ensure use of insecticides only when required and at the correct life stage of the insect being targeted,
  • rotating between insecticide groups to minimise the risk of insecticide resistance (check out the CropLife website for more information on this).

Issue 9 of Vegenotes, a publication created by Ausveg, describes these measures in greater detail.  There are some useful websites with excellent information; check out the Queensland Government’s Department of Agriculture and Fisheries website, and Cesar.

To stay connected with BFVG and for further resources/information on events in the Wide Bay-Burnett region, go to our website or subscribe to our Fresh Pickings newsletter.

Sources:

  1. Asgari, S. (2016) Manipulation of regulatory microRNAs to suppress insecticide resistance in diamondback moth. The University of Queensland.
  2. Ausveg Limited (2008) Vegenotes Issue 9 – Diamondback Moth.
  3. Queensland Government. (2012) A-Z List of Horticultural Pests (website).

Acknowledgements: 

Funding for the VegNET National Vegetable Extension Network program is from Hort Innovation.