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Pests > Pests Entities > Insects > Flies > Fruit fly > Drosophila suzukii, a new threat
February 2010. Because of the novelty of the find, Pestnet is putting up information on The spotted wing Drosophila –Drosophila suzukii, for ease of reference. However, there is much more info available on the Internet.
Here is an article by Bas VerhagenMAFBNZ, New Zealand.
The vast majority ofDrosophilaspecies (vinegar flies) infest overripe and fallen fruit.D suzukiiis one of only two knownDrosophilaspecies that are plant pests, attacking healthy ripe fruit.
D suzukiiattacks the fruit of a variety of crops, including apple, blueberry, cherry, grape, peach, persimmon, plum, strawberry, kiwi berries and Asian pears. In the laboratory, it has also been shown to attack tomato.
D suzukiiis endemic to parts of Asia (China, Korea, Japan and Thailand) but has also become established in Canada and Spain, and most recently in some parts of the USA (California, Florida, Oregon and Washington). To date, no interceptions at the New Zealand border have been identified asD suzukii; however, unidentifiedDrosophilaspecies have been intercepted 24 times on grapes coming from the USA, and three interceptions of unidentifiedDrosophila species were detected on peaches from China, two of which were alive.
Adults are small (about 2 to 3 mm in length), with straw-coloured bodies and red eyes, and are, therefore, very similar to the well-known vinegar fly,Drosophila melanogaster.D suzukiimales have a distinctive black spot on the outer edge of the wing and two darkened bands on the forelegs. Females do not have wing spots and can only be identified asD suzukiiby an expert. Like mostDrosophilaspecies, nothing is known about the larvae ofD suzukii.
D suzukiiis able to thrive in cool temperate climates. In Japan, there appear to be about 15 generations a year, the shortest life cycle lasting 8 days. Adults are known to survive the winter by hibernating in sheltered places. Adults are made motionless at 5 degrees Celsius, begin to crawl at 10 degrees and are most active at about 20 degrees.
D suzukiifemales can each lay around 350 eggs; these are laid inside the fruit while it is on the tree. The female penetrates the skin of the fruit using an ovipositor and lays on average two to three eggs per fruit. Often more than one female will deposit eggs into a single fruit, so that as many as 65 adults may emerge from a single cherry. The larvae feed and develop inside the fruit. The pupal stage can be in the fruit, but also in the soil.
In Japan,D suzukiiis a serious pest which infests among others cherries and grapes. The percentage of cherry fruits infested can be up to 75%. Recently, in the USA, losses of one-third of the cherry crop and losses up to 80% in peach orchards were reported from newly infested sites. Wounds are open to fungal and bacterial infections and secondary pests that may contribute to further fruit deterioration. The vectoring capabilities ofD suzukiiare unknown, butDrosophila species have been implicated as vectors of plant pathogenic fungi and bacteria.
Fresh fruit can harbour viable eggs, larvae and pupae. As egg laying occurs near harvest time and early symptoms are subtle, recently infested fruit can easily go undetected in a shipment. Oviposition scars are very small and eggs are very difficult to detect.