PestFacts Issue 9, 2019
There have been several reports recently across the state, particularly on Eyre Peninsula, of spray failures using synthetic pyrethroids to control Helicoverpa larvae. Agronomists reported failures using Cypermethrin and/or Cyhalothrin-based insecticides.
Spray failures can be due to multiple reasons such as application when caterpillars are inside pods where they cannot be reached by insecticide, or incorrect identification of the species (See The Beatsheet’s ‘Helicoverpa – identification and behaviour’ article for a breakdown on differences between species, or send us a sample for identification (free service, see below)).
We collated the following information with help of Dr. Lisa Bird (NSW-DPI):
Pyrethroid (group 3A insecticides) resistance in cotton bollworm (PDF 1.1 MB) (also called corn earworm), Helicoverpa armigera, is very frequent and extremely high (>90%), as is resistance to some group 1A pesticides (carbamates). Native budworm (PDF 938.8 KB), Helicoverpa punctigera, is not known to have developed SP resistance (so it is very important to let us know if you have spray failures).
Resistance in cotton bollworm is based on metabolic detoxification by cytochrome P450, conferring resistance to multiple pyrethroids. Increasing pyrethroid dosage by combining Karate Zeon and Trojan (two Cyhalothrin based insecticides) is inefficient, increases resistance selection and might cause a risk of residues above MRL.
Do not try a different pyrethroid when spray failure occurs, in such cases insecticides from other activity groups (group 1 organophosphates, 5, 6, 31,… , only if registered for the crop), can be used. Using a more selective pesticide will also not impact on beneficials that are very active in spring. Viruses (group 31) are reported to be effective for Helicoverpa control in Queensland.
On peas and lentils at Port Broughton Helicoverpa larvae (species unconfirmed) survived an application of Trojan, however it worked perfectly fine on beans. This could be due to climatic conditions, with very warm days inducing the unusual behaviour of larvae hiding inside the pods where the insecticides do not reach them, or the two populations not being the same species. Helicoverpa larvae (species unconfirmed, but believed to be native budworm) have also been reported at Auburn, Saddleworth and Tothill on canola.
If you have a spray failure please report it to PestFacts SA:
Phone: 08 8429 0682 or 0429 547 413
Maarten van Helden
Phone: 08 8429 0642 or 0481 544 429
Email: email@example.com .
Sources of reports: Sam Modra (A.W. Vater & Co.), Mark Habner (Landmark, Cummins), Iain Tod (Kerin Agencies Landmark), Clint McEvoy (Landmark Streaky Bay).
We provide free identification services to PestFact SA subscribers (subscribe here) if you would like a confirmation of species. Ideally, we would like at least 20 individuals. As many pests are cannibalistic, please provide them with some food (plant material) for eating and fill the rest of the container with scrunched up paper towel/newspaper as a place for larvae to hide and to absorb excess moisture. Please collect and send earlier in the week to make sure it does not stay in the mail over the weekend. Ideally, a study container is best, or use a box to protect the container, as they can get damaged or squashed in the mail.
Helicoverpa trapping network update
In most locations, we are now wrapping up the Helicoverpa moth trapping program for this year. We will continue to update to the Weekly Helicoverpa Updates page until all areas no longer find the information relevant. Many thanks to our volunteer trappers for your effort and participation: Andy Bates, Chris Davey, Adam Hancock, Ben Farmer, Troy Maitland, Sarah Meyer, Nigel Myers, George Pedler, Wez Schidmt, Steve Richmond, and Iain Todd.