It seemed as if nothing could stop my prolific raspberry bushes from running their marathon harvest. And then the worms came.

I started noticing them a little here and there. No big deal, right? I’d just soak the raspberries in salty water {how-to here} and dump off the dead floaters. But then what began as a small nuisance suddenly became an unmanageable infestation.

Where were these worms coming from?!

Spotted Wing Drosophila

My guess was that they had something to do with all of the tiny little gnats I’d noticed swarming around my bushes. See that fly on my raspberry there? Look closely, I’m working with a point and shoot camera here. Turns out, I was right. Those teeny, almost translucently white worms are the larvae of fruit flies. The Spotted Wing Drosophila is one type of fruit fly which is becoming a particular problem.

The difference between the SWD and regular fruit flies, besides the tell-tale black spot on the male fly’s wings, is that while everyday fruit flies generally lay eggs in overripe or damaged fruit, Spotted Wing Drosophila have a more aggressive approach. They lay their eggs in the flesh of underripe fruit, making it hard to beat the bugs to the harvest. The eggs hatch, and those nasty little worms are soon to follow.

These pests are actually relatively new here, and are becoming a HUGE pain to berry growers across the US. Not only do they effect raspberries, but blackberries, blueberries, cherries and strawberries as well.

Experts are still testing different methods of control, but there are a few preventative measures you can take to reduce the chances of an infestation:

  • Keep plants picked of ripe fruit. Ripening fruit will attract the Spotted Wing Drosophila, and will spread breeding grounds. Do not leave overripe berries on the vine, and do not let them fall to the ground as this will encourage an infestation. Pick the vines clean, and do not compost unwanted berries. The heat from the compost is not high enough to kill the SWD larvae and they will reemerge the following year. I’ve been feeding my overripe berries to the chickens, but you can also seal them in a ziploc bag and leave it out in the sun to kill the worms. You must keep your plants picked clean of all ripe fruit every single day.
  • Keep plants pruned. Fruit flies like humid, shady environments. Thin ’em out and keep sprawling varieties trellised. Burn the prunings instead of composting them.
  • Do a ground clean up. SWD larvae can overwinter in the soil and reemerge the following year. It is recommended that you cultivate the soil around your plants to expose the larvae to the elements. They don’t survive well in very cold or hot temperatures. I’m going to go an extra step and sprinkle Diatomaceous Earth around my plants after I thin them out.
  • Set traps. You can put out a vinegar or yeast-sugar trap to lure these pesky flies. It won’t catch enough of them to help a bad infestation, but if you set the traps out when the fruits are just beginning to appear, you will be able to monitor the arrival of the flies. Setting traps at the end of the season might also help reduce the population for the following year. Page 2 of this document explains how to make your own fruit fly traps.
  • Cover your plants. You may be able to prevent the flies from landing by covering your plants with a very fine row cover before the fruit even begins to appear on your plants. Be sure to close it off so that flies cannot get underneath it. This method, however, can sometimes pose problems with air circulation.
  • Harvest in Spring not Fall. Fruit flies tend to be more of a problem with Fall crops, particularly beginning in July. If you have an Everbearing variety, you might want to prune them after the Spring harvest so that you don’t get a Fall harvest that would attract the SWD.
  • Spraying. There are two organic insecticides which have been found to be helpful in reducing SWD population: Entrust and Pyganic.

I can’t tell you how frustrating it is to pick quarts and quarts of gorgeous red berries just to open them up and find worms crawling all over them. I’ve continued soaking them in the salt water solution and rinsing, rinsing, rinsing, until all of the worms are gone- then freezing them. This is just one of those mind over matter deals. I’ve resolved that if I end up eating a couple of worms, as long as I didn’t see them first, I’m good with that. Next year, I hope to be ahead of the game.

What about you, have you had trouble with worms in your berries this year?? What are you doing to treat the problem?