Monday, August 24, 2009

Meet the Beetles! Green Fruit Beetles, That Is...

     You may be hearing a ferocious buzzing as you are picking the backyard tomatoes, figs, corn and berries these days. You just might be disturbing the eating habits of the green fruit beetle (Cotinis mutabilis), munching away at the overripe and damaged fruits and vegetables in your garden. It's not just the sound that will stop you in your tracks. The combination of the biplane-like buzz as well as the sight of these slow flying, large (an inch and a quarter long), metallic green-shelled creatures might make you drop your crops.

Entomologist Baldo Villegas of the California Department of Food and Agriculture says his office has noted the growing presence of green fruit beetles in southern Sacramento County, beginning a few years ago. Until the 1990's, they had only migrated as far north as Fresno.

     "This beetle is now widespread from Mexico to the southwest and into northern California," says Villegas. "They are migrating northward fast." Villegas explains that the beetle is more vexing for backyard gardeners than commercial growers. "I consider them a nuisance pest," says Villegas. "They feed on rotting or open fruit and are attracted to them by the gas emitted by the fruit."


A native of Mexico, Villegas recalls the green fruit beetle as a harbinger of summer. "We used to catch them on fruit damaged by birds or in rotting fruit laying around on the ground," says Villegas. "We would tie a piece of string on one of their hind legs and that would allow them to fly along side of us."


Unlike a balloon on a string that escapes your grasp, the green fruit beetle is not going to drift away, high into the sky. Right now, those beetles are laying their eggs in your piles of garden compost, manure and mulch. So, the best control is to remove any such piles from the areas where you have seen the feeding adults. Turning the piles frequently will expose the larval stage of these beetles, a C-shaped, creamy white grub. Hand picking or flooding the area for two days can limit these noisy munchers during the next gardening season. And, chickens consider those grubs a delicacy.

To limit the spread of the adult beetles now, take away their food supply: fruit that is getting too soft on the vine. Trapping might be somewhat successful, according to UC Davis Integrated Pest Management Director Mary Louise Flint. In her book, "Pests of the Garden and Small Farm," she says that the green fruit beetle can be attracted to a half-filled one gallon jar, containing a 50-50 mix of peach or grape juice and water. Make a funnel out of small mesh wire and place it in the jar's opening. This will allow the beetles to get inside, but not back out. Insecticides are not recommended against the adult green fruit beetle.


  1. i have a blue beetle, with an orange dot on its back; finding them on tomatoes and other items in my garden - would you happen to be able to ID this one for me?