Spotted wing drosophila?Drosophila suzukii
Larvae of the spotted wing drosophila (SWD, Drosophilidae) feed in cherries throughout the state and in blueberries and occasionally caneberries and strawberries mostly in coastal areas.
Identification
The legless, whitish larvae at maturity, and the cylindrical, brown to yellow pupae, are about 1/8 inch long. Adults are flies about 1/10 inch long with red eyes and a brown thorax. The female's egg laying creates a small puncture in a depression on the fruit surface.
Male D. suzukii can be distinguished from most other Drosophila spp. by the dark spot near the tip of each of their two wings. Other similar-looking Drosophila spp. vinegar flies, or common fruit flies, mostly feed in fermenting, injured, or overripe fruit.
Larvae of true fruit flies (Tephritidae) also feed in the pulp of fruits and certain other crops. Pest tephritid flies in California include apple maggot (Rhagoletis pomonella), olive fruit fly (Bactrocera oleae), and walnut husk fly (Rhagoletis completa). Adult tephritids and mature larvae (pale maggots) are about 1/4 inch long, considerably larger than the spotted wing drosophila and other vinegar flies.
Exotic tephritids such as the Mediterranean, Mexican, and Oriental fruit flies are periodically introduced and have apparently been eradicated. Take any tephritid flies or maggots you find in fruit to the county agricultural commissioner or your local UC ANR Cooperative Extension office for identification unless you are confident the species found is already known to be established in California.
Life cycle
Spotted wing drosophila adult females lay eggs in fruit just as it begins to develop its mature color. One to several larvae feed in each fruit, causing it to soften and become decayed. After maturing, the larvae partially or completely exit the fruit to pupate. There may be up to 10 generations per year.
Damage
Spotted wing drosophila attacks healthy ripening fruit and damaged or split fruit. The female's ovipositor creates a small puncture in a depression on the fruit surface. Maggots feeding inside the fruit cause the flesh to turn brown and soft. Fruit may decay from secondary fungal and bacterial pathogens and drop.
Solutions
Traps help detect the presence of spotted wing drosophila. If trapping identifies that SWD is present, or you had this problem last year, insecticide can be applied.
Removing and destroying infested fruit and fruit on the ground may help to reduce infestation of later-maturing varieties. Fine netting ≤0.98 mm mesh (e.g., made for no-seeums) placed over hosts before fruit begins to color or ripen may help to reduce infestation if it is well secured to exclude the flies.
Spotted wing drosophila can be controlled by applications of spinosad, if the sprays are well timed. Monitor fruit and make the first application when fruit begin to change to their mature color. Because some varieties ripen early, others late, and more than one variety may be grown together, the total number of applications depends on what varieties are grown and temperature.
In cherries, make the first application as fruit turns from yellowish to pink (about 2 to 3 weeks before harvest). Spray each variety at least a second time 7 to 10 days later, the shorter interval if temperatures have been warm and longer when it's been cool.
In blueberries, apply an insecticide when the first berries begin to turn from green to pink. Make a second application prior to harvest. Treatments may be warranted at 7- to 14-day intervals until harvest is over.
Follow the product label directions, including the preharvest interval, or minimum number of days to wait after the last application before harvesting fruit. See the Pest Notes: Spotted Wing Drosophila for more information. |
