Try This Technique: Captive Bees Under Row Covers

| 7/30/2008 10:49:57 AM

Tags: row covers, pollination, captive bees, beneficial insects, pollinators,

Following our March story on row covers, several readers asked about the biggest weakness of row covers as a pest protection method, which is this: When the covers are removed to admit pollinators, pests like cucumber beetles and squash vine borers have free access to the plants.

Maybe there’s a better way. After reading about an ongoing study in Pennsylvania in which reared bumblebees are being used as pollinators for squash being grown beneath row covers, I decided to try a similar strategy. When a planting of ‘Boston Pickler’ cucumbers (grown under cover to exclude cucumber beetles) began blooming heavily, I went out in the cool of the morning, caught a bumblebee in a jar, and released it beneath the row cover.

The bee disappeared for a day, but the next day there he was, working away at the cucumber blossoms. That evening, I opened the cover and let him go. He had earned his freedom.

Four days later I was picking cucumbers, so I repeated the experiment with another bumbler and a pair of honeybees. I soon learned that when free-foraging bees are taken captive on a warm, sunny day, they lose all interest in blossoms and spend their energy fighting the row cover instead; there are stories of dead bees littering the ground when healthy hives are placed inside greenhouses. Adding a shade cover (a lightweight cloth spread over the row cover) goes a long way toward helping pollinators focus on the job at hand. I’ve also observed that bumblebees adapt much better to temporary detainment than honeybees. 

If you decide to try this technique, let us know how it goes! Please post a comment below.

The earliest fruits from these ‘Boston Pickler’ cucumbers were pollinated by bees released beneath a floating row cover: 

Joyce Fisher
2/3/2009 11:48:57 AM

Mark Gleason, ISU plant pathologist, wrote up a very interesting article about this very subject. We are definitely trying this method this coming summer. Here's is the link: Sounds like no wilt AND earlier cukes AND happier well-fed bees!!!

Barbara Pleasant_3
8/2/2008 11:40:07 AM

Thanks to all for your thoughtful comments. Kate and Vickie, you are so right to advocate the right of bees to freedom. When trying this little tek, honeybees were so unhappy that I released them after five minutes. Some individual bumblebees, however, took right to the task. Even though the longest I detained any individual bee was 3 days, I eventually did find the situation morally distasteful. On the hand pollination question, cucumbers are not quite as easy as squash, but you can spread the pollen about pretty easily with a small dry artist's paintbrush. During the morning hours (prime time for pollination), dab the centers of blossom after blossom, male and female. It's not easy because there are so many flowers. Better alternatives include using varieties that resist bacterial wilt, or self- fertile hybrids, which make visits by pollinators unnecessary. I'm mostly interested in small pickling cucumbers for making fermented dills, and I'd like to work with an OP variety so I can save my own seeds. My first planting, Boston Pickler, was a poor choice because it is susceptible to bacterial wilt. I got smarter for my second planting and chose resistant National Pickling. Next year I plan to grow Little Leaf, because it's resistant and I think the fruits are easier to see to pick. In my experience, when a strong variety gets rowcover protection until the plants bloom, it becomes an unstoppable train despite cucumber beetles and other pests. But when you've messed up and planted a susceptible variety like I did, it's easy to let fear and impatience push you to try extreme measures.

Francene Greene
8/1/2008 11:29:25 AM

This is perhaps a silly question, (I am new to gardening): how do you pollinate by hand as recommended by a previous comment?

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