Over wintering fruit fly
Queensland fruit fly numbers were high last season due to the La Nina weather pattern and a shortage of harvest labour resulting in excess fruit left on trees and the ground. It is likely higher than normal numbers of adult flies have entered the winter season and sought refuges in warm spots where they may survive until temperatures increase (Queensland fruit fly do not hibernate in the ground over winter).
These refuges exist in evergreen trees such as orange, lemon, grapefruit, feijoa, olive, loquat, guava and avocado located in urban and peri-urban areas and near houses and buildings on farms. Inspection may reveal fruit fly in a slow metabolic state on the under-side of leaves of lemon and other evergreen trees.
When temperatures rise above 16°C flies become active and seek out food sources and a mate to breed. You can gauge whether Queensland fruit fly is present on your property by hanging fruit fly monitoring traps (male-targeting para-pheromone traps) to detect any build up and then start baiting.
Act early by bait spraying
A bait spray is a mixture of protein bait attractant (usually a yeast liquid), mixed with a small amount of insecticide (organic options are also available). Approximately 50ml is applied as a ‘spot spray’ to the trunk or foliage. There is no need to spray the whole tree. Target loquats and late-hanging oranges to reduce first generation post-winter fruit fly adults.
Female flies need to feed on protein before laying eggs. They are attracted to the protein and when ingested, the insecticide kills the fly before egg laying occurs. Apply bait sprays at weekly intervals and re-apply bait immediately after rainfall of 2mm or more. Baits should be applied as high in the foliage or trunk as possible.
If you do not wish to use a chemical insecticide, alternative products are available, including a natural bait spray mixture, which contains a bacterium (registered for organic use), instead of a chemical insecticide.
Benefits of bait sprays
Benefits of bait sprays include the process of spot spraying instead of cover spraying. Bait spraying is environmentally friendly and has minimal impacts on pollinators and beneficial insects. For more information about bait spray products and their application, contact your local supplier.