Your Guide to Easy Fruit Tree Care

Episode 46: Fruit Trees and Spotted Wing Drosophila

Spotted wing drosophila (SWD) is a fruit fly that's on the move. And unlike other fruit flies that target mostly rotting or fermenting fruit, SWD targets fruit right on the tree, laying their eggs in the young fruit and eventually turning it into a wormy mess.

Spotted Wing Drosophila lay their eggs under the skin of cherries and other fruits. Photo credit: Nikki Rothwell

SWD targets a wide range of crops including cherries, apricots, plums raspberries, currants, and elderberries. The bad news is that spotted wing drosophila is spreading across North America, benefiting from our warming climate.

Can we do anything to protect our crops from spotted wing drosophila without resorting to toxic pesticide sprays?

According to Nikki Rothwell of Michigan State University's Northwest Michigan Horticulture Research Centre the answer is yes.

She has found that there are ways to make our orchards less hospitable for SWD. Simple tools like pruning and orchard floor maintenance are a large part of the equation. Nikki tells us all about it during this episode of The Urban Forestry Radio Show and Podcast.

What you will learn about fruit trees and spotted wing drosophila in this show

  • 3:00 Susan introduces SWD and explains why these flies are a problem in orchards growing sour cherries, raspberries, plums and other fruit.
  • 5.03 How Nikki got involved in studying spotted wing drosophila back in 2010 and why the problem is so serious.
  • 5.53 What is the drosophila species and how quickly do they multiply in a lab and in an orchard?
  • 7.28 How does winter affect spotted wing drosophila?
  • 9.21 How SWD is affecting the tart cherry industry in Michigan.
  • 10.00 What is the zero tolerance policy in terms of tart cherries and SWD in Michigan?
  • 11.31 Spotted wing drosophila eggs and larvae are tiny. How would you know if a cherry you are harvesting or eating is infected?
  • 12.50 What does an orchard that's infested with SWD smell like?
  • 14.20 Why spotted wing drosophila prefers fruit that's already infested.
  • 14.50 Donnie from Connecticut asks: What's the best way to fertilize your fruit trees?
  • 16.20 What are the organic sprays that might work on spotted wing drosophila?
  • 17.45 What is the extent of the spread of SWD in North America?
  • 19.29 Are spotted wing drosophila also interested in sweet cherries and raspberries?
  • 21.20 How SWD problems affect peaches and apricots.
  • 22.06 What can consumers do to wash any spotted wing drosophila larvae off of the cherries or blueberries? How does brown sugar solution irritate the larvae?
  • 24.00 Is it dangerous to eat SWD larvae?
  • 30.20 How Nikki started researching solutions to the problem and the role of pruning in protecting the trees.
  • 31.05 How tart cherries are traditional grown on full size root stock and how they are traditionally pruned and harvested.
  • 34.43 How does Nikki's pruning technique affect these insect pests?
  • 35.25 How a light monitor will help researchers decide how much pruning to do in order to open up the canopy enough.
  • 36.20 Bev asks: Are the flies surviving the winter in fallen fruit? Would cleaning the orchard help rid it of these flies?
  • 37.57 Ben asks: Will eating large numbers of these flies in cherries damage human health?
  • 39.43 Roz from Ottawa asks: Would tree covers  or netting protect fruit trees from SWD?
  • 41.57 Tisha from California writes: We should all watch the film The Biggest Little Farm which shows how biodiversity can help to protect food crips from insect problems like this.
  • 50.24 Nikki talks about why mowing the orchard helps to protect the fruit trees from spotted wing drosophila.
  • 53.21 Does humidity in the orchard mean that there will be higher numbers of SWD?
  • 54.24 Are tall grasses also not good to have in your orchard? Or do these grasses have a positive role to play?
  •  56.27 How hopeful is Nikki that we will be able to overcome SWD problems in orchards in the future?

Spotted wing drosophila (SWD) is a fruit fly that's on the move. And unlike other fruit flies that target mostly rotting or fermenting fruit, SWD targets fruit right on the tree, laying their eggs in the young fruit and eventually turning it into a wormy mess.

Listeners who emailed us during the show were entered into our contest to win a free pass to's fruit tree pruning masterclass Valued at $149!  In the course you learn how to use pruning to improve tree health and productivity. You'll also learn specialist pruning techniques including decorative espalier pruning and pruning high-density style orchard trees.

The host of the Urban Forestry Radio Show and Podcast is Susan Poizner of the fruit tree care education website and the author of the award-winning fruit tree care book Growing Urban Orchards. You can listen to previous episodes of The Urban Forestry Radio Show and Podcast at and you can subscribe to the iTunes podcast.

Tune into The Urban Forestry Radio Show LIVE by going to on the last Tuesday of every month at 1.00 pm Eastern Time and email your questions in during the show to [email protected] This show covers fruit trees, food forests, permaculture and arboriculture. After the live broadcast, archived podcasts are available at

The Urban Forestry Radio Show and Podcast is brought to you by our Gold Sponsor, Stark Bro's Nurseries and Orchards . Our bronze sponsors include Whiffletree Nursery, Earth Alive, and Mark's Choice.

Click below to listen to the archived podcast now!

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Susan Poizner of Orchard People

Speaks at conferences and symposiums across North America about fruit tree care, urban orchard design, fruit tree cultivars and more.
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At Orchard People we are careful to select sponsors who offer quality products and services for fruit tree growers. Click their logo to learn more about them!

Earth Alive
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