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Pest management strategies for spring
 
By Urban Harvest

It often comes as a surprise to many people that only 1-2 percent of all insects are considered to be pests of man. Even those insects considered to be pests serve a role as part of the food chain; although, several insects such as fire ants, termites, mosquitoes and fleas often require specialized management. Beneficial insects are those that help us by pollinating plants, recycling organic matter, attacking pests and by performing other such helpful deeds.

The following are a few of the strategies gardeners can implement to attract and sustain a healthy variety of beneficial insects.

STEP ONE: Take a pass on using harsh, persistent products in the landscape that kill a broad variety of insects including beneficial insects. Instead, choose the least-toxic, most selective and least disruptive products that are available as needed. These products and the insects and their target pests include citrus oil (fire ants, scale, chinch bugs), garlic oil (spider mites, lacebugs), insecticidal soaps (aphids, thrips), microbes such as Bt or Bti (worms, mosquito larvae), neem oil (lacebugs, leaf miners), liquid pepper (many insects) and soybean oil (whiteflies).

STEP TWO: Gradually change out pest-prone plants with tougher, better adapted plants that are resistant to pests. Seek out a multitude of plants that also are known to attract beneficial insects. Some homeowners often pay for unnecessary, extra landscape treatment applications due to just a few problem prone plants that could easily be phased out, reducing the level of maintenance and expense.

STEP THREE: Observe and identify insects before making treatments. Since most of the insects in your landscape are helpful, it pays to identify them before taking action. At times, it might seem like a specific insect is guilty of being a pest; however, it often turns out that an insect under suspicion has moved in to take care of the real culprit. The Texas Bug Book by Malcolm Beck and Howard Garrett is a helpful identification guide filled with pest management solutions. Even when an insect is confirmed to be a pest, it often makes sense to give nearby beneficial insects some time to move in and help out. Some of the more common types of beneficials to get familiar with include: ladybug larvae as well as the adults, lacewings (not to be confused with lacebugs), assassin bugs, big-eyed bugs, parasitic and predatory flies (hover, robber, syrphid, tachanid and), parasitic wasps (braconid, ichneumonid and trichogramma), spined soldier bugs and ground beetles. It should be noted that parasitic wasps do not sting people.

STEP FOUR: Provide water sources for beneficials to help them endure dry stretches. Ponds, bird baths and other water elements work well. Landscape beds enriched with compost and topped off with a layer of mulch and lawns insulated with recycled clippings often retain enough moisture to sustain beneficials through dry periods. Mosquito dunks can be added to bird baths, ponds or other elements to kill mosquito larvae, while not harming beneficials. The naturally occurring bacterial strain Bacillus thuringiensis israelensis (Bti) is the active ingredient in Mosquito Dunks (donuts).

STEP FIVE: Recycle organic matter such as fallen leaves, and use the leaves as mulch to help provide shelter for the extremes of summer and winter. The larval stages of many types of beneficial insects such as ground beetles (they eat slugs) need organic matter as a food source.

STEP SIX: Plant your own "field (landscape) of dreams." It does sound corny, but in the case of attracting beneficial insects to your landscape, "if you build it" (nectar producing plantings), "they (the beneficials) will come." That's right, in most cases you do not have to buy beneficial insects such as ladybugs. However, in some cases (especially commercial growing operations), it can make sense to introduce (purchase) beneficials such as lacewings that are more likely to do the job and stick around.

Most adult stages of beneficial insects survive by feeding on nectar. Nectar producing plants to consider adding this spring include: brown-eyed Susan; fennel; heirloom pentas, lantana; Mexican hat, Mexican milkweed, native asters (by seed), passion vine, sunflowers, tropical sage (scarlet sage), verbena, wild ageratum (by seed), winecup, and yarrow.
Consider adding plants to ponds or bog gardens such as pickerel rush, arrow-head, tuckahoe and lizardtail to attract dragonflies and damselflies, both of which are voracious predators of mosquito larvae and adults.

Mexican milkweed is a "must add" element due to its value as a beneficial insectaries plant. This sun-loving plant is not only a host plant for the Monarch butterfly, but it is also helpful as a trap plant. Mexican milkweeds regularly harbor a small population of aphids on the upper portions of their stems. The plants tolerate the aphids very well, and some aphids will be present on the plants year-round, providing a steady, ongoing source of food for beneficial insects. With a steady food supply, a wide variety of beneficial insects including assassin bugs, ladybugs, lacewings, hover flies and others will be more likely to stay around all year. For those of you who have a crape myrtle or two or bush beans, Mexican milkweeds will help keep aphids from posing as much of a problem for those plants.

And finally, many gardeners end up with a new source of entertainment as they discover, observe and learn more about the insects that visit their landscapes.

This column is produced by Urban Harvest. Learn about gardening classes, community gardens and orchards, farmers' markets, and more at www.urbanharvest.org. This article was written by Mark Bowen who is a knowledgeable resource in native plants, food access issues, organic gardening, co-author of “Habitat Gardening for Houston” and former executive director of Urban Harvest.