What's up With the Worms in My Cherries? It's the Spotted Wing Drosphila
The Spotted Wing Drosophila, Drosophila suzukii, is a new pest that has recently arrived the Klamath-Trinity region. It's a small fruit fly that lays several eggs in ripening cherries. The worms hatch out and burrow through the flesh, turning the fruit brown and ruining it. The real bummer is that this same pest will infest other fruits such as berries, persimmons and stone fruit.
Control - Trapping is used in commercial orchards to detect and monitor fly populations. While trapping has not proven to be an effective control in large orchards, it could make a difference in the more remote and isolated homestead gardens and farms found in our area. Traps are easy and cheap to make using any plastic containers baited with apple cider vinegar. Each adult female fly lives up to two weeks and can lay up to 100 eggs a day, and each trap will catch dozens of flies, so trapping makes a difference. Hang traps as soon as you start to see some color in the fruit and look for small flies with the identifying two spots on the wing. (See below). Avoid over watering fruit trees and berries as this splits the fruit and attracts more flies. Harvesting ripe fruit promptly and disposing of damaged fruit by either bagging it up or crushing it and letting it dry in the sun will reduce the fruit fly population. Most insecticides are broad spectrum and will kill beneficial insects such as predators and honeybees as well as the target pest. Spinosad is an organically approved insecticide that has been shown effective controlling the Two Spotted Drosophila.
How to Trap the Two Spotted Drosophila - You can use any plastic container with a firm lid to make a trap, plastic soda/water bottles, or yogurt containers work great . Clean out the container, drill 5/16 inch holes around the perimeter, and place a few inches of vinegar with a few drops of dish detergent. Drill two holes on opposite sides near the top of the container and string a wire to hang the trap in a fruit tree. One container will trap scores of flies, and each female lays over 1,000 eggs, so you are preventing thousands of infestations by trapping!
This bulletin from Oregon State University Extension has a good description of the pest as well as how to make traps for monitoring. This UC Pest Management Guide has more detailed information and links.