The spotted wing drosophila (Drosophila suzukii) is a small vinegar fly that was first discovered in the United States in 2008 and since that time has moved throughout the country and into our state. It is a very tiny fly, a small fraction of an inch, so cannot fly far.
John Ball, Forest Health Specialist SD Department of Agriculture, Extension Forester SD Cooperative Extension
How did it get everywhere so quickly? You guessed it – people and their vehicles.
This fly is a problem with small fruits, in our state the currants, elderberries, grapes, raspberries, and strawberries. It also will infest aronia and cherries. It is becoming a major headache as the female cuts into the ripe fruit with a saw-like ovipositor to inject the eggs beneath the thin skin of the fruit. The eggs hatch in one to three days and the larvae quickly swarm the inside of the fruit rendering it into mush.
There is nothing [worse] (well one thing) than collecting a tray of raspberries, placing them in the frig and the next day having nothing but a tray of slime. The “one thing?” Biting into the fruit and noticing an off-taste and texture and realizing you ate a fruit-filled with these worms! Yum! You might not notice them at all and according to the literature eating them is not harmful to humans – just gross.
The short life cycle means that there are multiple generations per year so this insect can easily, and quickly, destroy a crop. Since the insect attacks only ripe fruit, fruit that will be harvested very soon, there are fewer insecticide options available to producers and home fruit growers. The insecticides are applied to kill the adults before they lay their eggs. Once the eggs are inserted into the fruit there are no effective treatments. Insecticides containing spinosad or Malathion, to name two possible treatments may be used but applicators must follow the label as to crops, intervals between treatments and interval before harvest.
The best way to tell when the insect is in the area (other than finding damaged fruit) is monitoring with traps. The insect overwinters in the leaf litter beneath windbreaks. Most do not survive the winter as the temperature below about 20°F are fatal, so it takes a while for the populations to rebound each year. This means we usually do not see the insect until late June to mid-July depending on the summer temperatures, so June-bearing strawberries and summer raspberries often escape infestations. It’s the day-neutral and fall-bearing raspberries that are damaged the most.
The insect will also feed on non-crops hosts such as common buckthorn and chokeberry. Producers that have their small fruits surrounded by windbreaks containing these and other fruiting plants such as snowberry may be creating a reservoir of the pest.
The information above is an excerpt from the July 17, 2019 | Vol. 17, no. 22 Pest Update published by the South Dakota Department of Agriculture and South Dakota State University.
Read the entire report here
Topics covered in this Pest Update:
- Japanese beetle adults are out feeding on foliage
- Spotted wing drosophila is infesting fruit
- A sad tale of planting too deep
- Sappy insects
- Herbicide injury on trees and shrubs
- Brown County (oak gall)
- Fall River County (catalpa winter kill)
- Jones County (hackberry nipple gall)
- Tripp County (fireblight on cotoneaster)