Native budworm

Native budworm (Helicoverpa punctigera) have become problematic in several cropping regions in northern Victoria and southern New South Wales. Grower, Bronwyn Hunt (Merriwa Pastoral Company), has reported finding an average of six larvae per ten sweeps in a crop of field peas near Kerang, in the Victorian Mallee district. The crop is nearing the end of podding and is showing some signs of damage including some pods found with grubs inside. Bronwyn recalls seeing moth activity in the paddock on the 18^th of September, and then finding first to third instar larvae on the 7^th of October. The crop will continue to be monitored given the current growth stage and the presence of some beneficial insects.

Agronomist, Bruce Larcombe (I.K. Caldwelll), reports finding small (2-3 mm) native budworm caterpillars in several canola crops around Shepparton, in the Northern Country district of Victoria. An average of 1-3 grubs were found per 10 sweeps when sampling with a standard sweep net, along with good numbers of beneficials including hoverflies, lacewings, parasitic wasps and some ladybird beetles. At this stage it is hoped that the crops will not require chemical treatment however they will be monitored very closely for the remainder of the growing season.

Native budworm have also been detected in several crops in both the Riverina and South-West Slopes districts of New South Wales. Agronomist, Bob Ronald (Landmark), reports finding significant numbers of mid-size larvae in a canola crop north of Albury, and says the affected paddocks are likely to be sprayed to prevent further crop loss. Bob also reports finding diamondback moth caterpillars in the same canola crops, however numbers are not of concern at this point in time.

Native budworm larvae grow up to 40 mm long and can vary significantly in colour, including shades of brown, orange and green. They typically have darker strips along the body and bumpy skin with sparse stiff black hairs. Crops that may be attacked include canola and most pulse crops, as well as pasture seed crops of lucerne, annual medic and clover. If chemical control of native budworm (or other spring pests) is required, it is important to keep in mind withholding periods (WHP) of chemicals, particular when nearing harvest. Always check product labels and remember that in canola ‘harvest’ includes windrowing, meaning products with shorter withholding periods (e.g. gamma-cyhalothrin and lambda-cyhalothrin which have a 7 day WHP) may need to be considered.

Click here for images of native budworm and refer to PestFacts Issue No. 10 for more information.