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Index : Pests
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- 12. Keep Good Bugs in Your Garden - Top
- If you see bugs on your plants, don't assume they're the bad guys. Less than 10% of all insect species are actually harmful plant feeders. Many others are actually beneficial to gardens and landscapes as they devour aphids, scales, whiteflies, mealy bugs and other bad bugs.
Beneficial insects include some we are all familiar with like adult lady bugs, preying mantids, and spiders. But others like lace wings, assassin bugs, big-eyed bugs and damsel bugs are not so recognizable. It's important to be able to identify these good guys so as not to apply garden sprays, even soap sprays, that could harm them. There are many web-sites with color photos of most of the beneficial insects. Reference books for identification are also available at libraries and local book stores.
The larval stage of some beneficials look much different than the adults. This is the case with lady bugs and lace wings. The larvae of these insects are rather ugly and easily mistaken for something bad. Lady bug and lace wing larvae look like little alligators, with numerous spines and wart-like structures. Lady bugs are blackish with some red, orange or yellow spots or bands. Lace wings, also called "aphid lions", are brown with cream-colored markings. The adult lace wing is light-green with a slender body about one half to three quarters inches long. It's name comes from the prominent, large lacy wings that are considerably longer than the body itself.
The best way to ensure a good population of these beneficial insects in your garden is to limit spraying with insecticides. Aphids and whiteflies, two of the most common garden pests can be easily controlled with soap sprays. But even soap can kill some beneficials, so limit your spraying to spot applications and only as-needed. Aphids can be controlled with a soap spray made by mixing one tablespoon of liquid dishwashing detergent in a gallon of water. Whiteflies are more difficult to control. They will require a mixture of two tablespoons of soap per gallon of water. Water sprays along are quite effective on aphids and mites.
To encourage good bugs, provide them with an alternative food source when meals of pest insects are scarce. Flowers produce nectar and pollen which are used as food by the adults of many beneficial insects. Set aside an area of your yard for perennial and wildflowers. Composite flowers (sunflowers, desert marigolds, etc.) are favorites with insects. Also attractive are plants of the Umbelliferae family, including carrots, celery, coriander, dill, fennel and parsley. Allowing these plants to flower will provide a good food source.
A source of water will also help attract insects. This is especially important during dry weather. Bird baths and other small, shallow containers are best suited for this purpose. Sticks or rocks placed in the water will serve as perches for insects to access the water. Keep in mind that standing water will also attract mosquitos. Either change the water twice-weekly or place a mosquito dunk (Bt) in the water to prevent mosquito breeding.
If you have one of those Bug Zapper lights for attracting and electrocuting insects, turn it off! Bug Zappers are known to kill more (60-70%) beneficial bugs than pests. People like the Zappers because they can see and hear them working. Most often they are purchased for mosquito control. But relatively few mosquitos are actually caught by these devices. Studies have found that populations of mosquitos in a typical yard are relatively the same with or without a Zapper.
Our recent rains have helped to cut down on the number of garden and landscape pests. Rains wash off most of the aphids, mites, and lace bugs (not to be confused with lace wings) from plant leaves and stems. Once dislodged, these bugs seldom find there way back onto the plants.
Finally, there is one beneficial insect that does seemingly eat plant leaves. It's the leaf-cutter bee, a great little plant pollinator. The leaf cutter doesn't actually eat the leaves, but rather uses the leaf pieces to construct her nest where she deposits her eggs. The cut is very precise in a half circle along the edge of the leaf. The favored nest building material comes from roses, bougainvillea, red bud and other soft-leaved plants. No real damage is done to the plants, just a little cosmetic injury that can serve as an interesting point of conversation with visitors.
Written by John Begeman, College of Agriculture and Life Sciences, the University of Arizona, 520-626-5161. - Updated: August 10, 2003
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