Try This Technique: Captive Bees Under Row Covers

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: