Spotted winged drosophila
Spotted wing drosophila (Drosophila suzukii) is a small fly that damages soft-skinned fruits, making them unfit for market.
Background
Spotted wing drosophila (SWD) is native to Southeast Asia and is found throughout China, India, Korea, Myanmar, Russia, Thailand, France, Italy and Spain.
In the USA, the insect was discovered in California on caneberries and strawberry plants. It has been established in Hawaii since 1980, and spread to Florida, Louisiana, Michigan, North Carolina, Oregon, South Carolina, Utah, Washington, Wisconsin, and parts of Canada.
Australia imports host fruit from the USA, including strawberry, cherries and table grapes – this could provide a potential pathway for SWD entry.
Impacts
Of the 3000 species of drosophila, this pest is one of two that can infest healthy crops, as well as damaged overripe fruit. This reduces crop yield and quality through direct feeding and secondary infection of the fruit.
Host fruits include berries, cherries, nectarines, plums, and grapes. SWD also target apples, pears and other fruit with thicker skins when they begin to rot.
Female SWD prefer to lay eggs under the skin of ripe fruit by penetrating the surface with a serrated tube (ovipositor), creating a small puncture.
Affected fruit does not show signs of infestation until the flesh starts to break down and discolour. White larvae can be seen in the rotting flesh. Their ability to remain hidden within fruit helps SWD spread, as the pest is not discovered before transportation.
Identification
Adult SWD are almost identical to the regular vinegar fly (D. melanogaster). They are between 2 to 3.5 mm long, with an amber coloured body, red eyes, and clear wings. SWD can only fly short distances.
The adult male has a distinct dark spot on each wing near the tip and 2 small dark bands on each front leg. The female is similar to other fruit flies, except for the ovipositor, unbroken banding of the abdomen, and sharply defined cross vein in the wings.
