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Ask the Master Gardener: Make your garden a welcoming spot for beneficial insects

By: Trish Grenfell Placer County Master Gardener
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Question: I have a backyard vegetable garden, which I am trying to grow organically. As a means of controlling insect attacks, I have been told to introduce plants that attract predator insects, which will destroy the bad bugs. So who are the good insects that will protect my vegetables and fruit? And how do I get them into my backyard? Answer: First of all, don?t use broad spectrum sprays that kill all insects. If you have a major insect infestation that is munching your veggies to death, you may want to use a selective insecticide such as Bt (Bacillus thuringiensis) for caterpillars. For more information on selectives that will be less harmful to your beneficial predator insects, please read http://www.ipm. ucdavis.edu/PMG/r107300811.html. (Note: The website insecticide information is not specific to citrus.) Remember, however, that the insect heroes won?t come and stay unless your garden provides them a food supply, so think twice before you spray a minor problem. The natural enemies of the insects you want to destroy are the lacewings, lady beetles (often called lady bugs), parasitic wasps, ground beetles, hover flies, tachinid flies, pirate bugs, damsel bugs, and big-eyed bugs. For more information, see this poster from UC Davis: http://www.ipm. ucdavis.edu/FAQ/natural -enemies-poster.pdf You can purchase many of these biocontrol insects at garden centers or even online, but there is no guarantee they will stay in your yard. You are on the right track when you ask about the plants that will attract and keep them on guard in your garden. The list of plants that attract them is long; A good website that matches the beneficial insects to the plants they will attract them is http:// www.farmerfred.com/ plants_that_attract_ benefi.html. If you have room, intersperse some herbs or flowers now amongst the vegetables. It is an excellent place to plant flowers you will use for cutting only. You don?t have to be concerned with the landscape design in your vegetable garden, so plant rows of asters, yarrow, prairie sunflowers, golden marguerites, zinnia, lemon gem marigolds, spike speedwell, feverfew, white sensation cosmos, sweet alyssum, lobelia, gloriosa daisy, English lavender, and/or statice. And there are herbs that will do the job also: dill, caraway, coriander, fennel, parsley, crimson creeping thyme (wonderful groundcover), and the aggressive spearmint, pennyroyal, and lemon balm in containers. Interplanting vegetables, herbs and flowers is how the original cottage garden style evolved. If you mix in your favorite plant attractors, you?ll eventually have beneficial insects patrolling your vegetable garden. Have gardening questions? Call the Master Gardener hotline at (530) 889-7388.