While gardening may seem like a pursuit aligned with nature, it can be argued that gardening is an unnatural idea. We attempt to grow a wide assortment of plants — many of which are not native to our region — in an orderly fashion, and we try to control insect, disease and other pest problems. Without a great deal of human intervention, a vegetable or ornamental display garden tends toward chaos, and may yield little if at all, whether our harvest is beauty or produce.
Many gardeners are interested in using fewer synthetic chemicals in an effort to garden as “naturally” as possible. Fortunately, a wide assortment of chemical-free pest management strategies is available for the home garden. Whether your garden philosophy is chemical-free, low chemical or even high input, here are some strategies that can help reduce the need for synthetic pesticides, saving money, effort and environmental impact. More strategies will be discussed in the next Plant Lovers’ Almanac.
Hand picking of insects works best for large, conspicuous insects, such as Japanese beetles, Colorado potato beetles and tomato hornworms. This is one of the simplest methods to manage insect pests, and is especially effective when the gardener is out in the garden at least once a day to track pest activity. When used in this way, hand picking can keep numbers down and may prevent larger infestations.
With Japanese beetles, for example, picking off and destroying the early arrivals can keep numbers down through the season. This is because the first beetles to scout the garden will send chemical signals to other Japanese beetles, alerting them to the bounty found in your yard. If the early arrivals are removed and destroyed, fewer beetles will find your garden.
In the case of Colorado potato beetles, all insect stages can be hand picked. The large, striped adults can be picked off early in the summer, before they have a chance to lay eggs. The orange eggs can also be removed, as can any hatching larvae seen on plants. If picked as small larvae, the beetles have little chance to cause significant damage. Other eggs can be hand picked, such as those of cabbage white butterflies noted on cabbage or kale plants. Collected insects can simply be dropped into a cup of soapy water.
Floating row covers
Floating row covers are permeable fabrics that cover vulnerable plants, providing protection from insect pests but allowing light and rain to reach plants as they grow. Since the fabrics are lightweight, they can rest directly on top of plants, and will rise as plants grow.
Floating row covers are not without their drawbacks, however. The fabric can be expensive, although it may hold up for several years. Covers must be in place before pests arrive, and must be removed for weeding. Row covers must be pulled back to allow for pollination of crops, such as cucumbers and squash. Still, floating row covers provide an important option for low- or no-chemical pest management, effectively excluding many species.
Other types of barriers can be used to physically exclude insect pests. Panty hose or foil can be used to cover the base of squash plants, thereby providing a barrier against squash vine borers. To deter cutworms, plants can be surrounded by paper or plastic cup collars. Diatomaceous earth is sometimes sprinkled around hosta and other plants to provide a physical barrier, protecting the plants from slug damage.
Syringing is a fancy term for using a spray of water to remove pests from plants. In their immature stages, insects are wingless. If these insects are dislodged from their host plants, they will be unable to fly back onto the plant. Syringing is a successful option for lacebugs on azaleas and pieris, sawfly larvae on roses, or aphids on just about anything.
One spray of water is rarely enough, however; plants must be vigorously sprayed several times to sufficiently reduce insect populations. For most insects, the jet of water must be targeted to the underside of leaves. Flying insects, such as Japanese beetles, or large larvae like gypsy moth caterpillars will not be successfully deterred by syringing.
Many pest problems are kept in check by beneficial insects. Beneficial insects, such as lacewings and ladybird beetles, need prey for the larval stage to consume as well as pollen and nectar to meet their nutritional needs throughout their life cycle. Beneficial insects are more likely to visit and take up residence when the garden is full of flowers high in pollen and nectar. Include beneficial-friendly flowers such as catmint, Shasta daisy, cosmos, marigold and hyssop in the garden. Early-flowering perennials are especially important to provide habitat for beneficial insects before pest species break out; in this way, the predators will already be in the garden when pests arrive.
Denise Ellsworth directs the honeybee and native pollinator education program for Ohio State University. If you have questions about caring for your garden, contact her at 330-263-3700 or click on the Ask Denise link on her blog at www.osugarden.com.