Drosophila flies, officially known as “Vinegar Flies”, but commonly called “Fruit Flies” have accompanied our fruits and vegetables in North America for centuries. Drosophila melanogaster, a standard subject for genetics studies, will lay its eggs on damaged fruit such as tomatoes, apples, etc. When gardeners harvest the fruit, the larvae rapidly develop and gardeners are left with small swarms of Drosophila in their house every fall until harvest is over.There are over 1500 species in the genus, Drosophila and many are not native to North America. One Drosophila species, Drosophila suzukii, the Spotted Wing Drosophila, is an invasive pest from Asia. It made its first appearance on the West Coast of North America, but has rapidly spread from coast to coast creating headaches for fruit growers nationwide. The Spotted Wing Drosophila attacks undamaged fruits, including raspberries, blackberries, strawberries and blueberries. The larvae burrow into the center of the fruit and destroy it before it can reach market.
Entomologists have devised monitoring programs for growers (also see here) that allow growers to time insecticide treatments to best control the pests. This creates an added expense as fruit growers who did not have to use expensive insecticides, must now treat their crops. Organic fruit growers find it difficult to manage this pest without insecticides and some are simply quitting raspberries. Although Spotted Wing Drosophila had previously not reached Maine, it has been reported in Maine this Summer (2012).
Invasive species change the economics and management practices for important food crops. They can impose substantial costs to growers who must pass them on to consumers. Consumers experience higher fruit prices and Spotted Wing Drosophila is partly to blame. The US government, through APHIS (Animal and Plant Health Inspection Service) seeks to prevent invasive pests from entering the US. APHIS costs taxpayers money, but the costs of an invasive species can be even greater.