If insect pests are bugging you, take a deep breath. No garden is without insects, and your goal should not be to eliminate insect pests, but rather to keep the pest population below the point that they do significant garden damage. Here's how to use integrated pest management principles to keep down three common garden pests.
IPM for Garden Pest Control
It used to be that a gardener's primary weapons were toxic chemicals. But scientists have found that this creates more problems than it solves.
Broad spectrum pesticides kill indiscriminately, taking out beneficial bugs and the natural enemies of insect pests. Chemicals also pollute water and soil and make animals and humans sick. Today, gardeners use a system called integrated pest management, preferring nontoxic methods of pest control before chemicals are considered.
Here's what to try for three common garden bugs: aphids, spider mites and leafminers.
Identify pest: Aphids are small, soft bodied insects often found in large groups feeding on plant leaves. Recognize them by their soft, pear-shaped bodies, long antenna and cornicle tubes at the back of the body. Aphids produce honeydew, a waste product that ants eat. If you see lines of ants heading up to your plants, it may be a sign of an aphid infestation.
Aphids pierce plant tissues to suck on the sweet juice. Since they reproduce prodigiously and transmit viruses, they can turn into serious pests. Look for stunted plant growth, deformed leaves or galls.
Prevention: Reduce high-nitrogen fertilizer that encourages aphid activity and keep down weeds that can host aphids.
Control: Monitor your plants regularly for aphids. When you first see aphids, use a strong stream of water to wash them off your plants. If that doesn't work, consider biological control. You can release lady beetles or parasitic wasps that eat aphids. Use horticultural or neem oil sprays or soap-based insecticides to smother the bugs. Save chemical pesticides for a last resort.
Identify pest: Tiny spider mites look like dots moving around on the underside of your plant leaves. They suck the juices from leaves, damage that appears as a stippling of light dots or yellowing leaves. Look for spider-like "webs" they spin on the leaves.
Prevention: Water your plants regularly. Water-stressed plants are more likely to be attacked. Avoid broad-spectrum insecticide, since this can cause mite outbreaks by killing off predator bugs. Water nearby walkways frequently to reduce dust, since dust keeps mite enemies away.
Control: If you see spider mites, blast plants with hose water to wash off the pests. Encourage natural enemies of spider mites, like predatory mites, by keeping dust and pesticide use to a minimum. Spray both sides of the plant leaves with insecticidal soap or horticultural oil sprays.
Identify pest: Leafminers look different in different stages of growth. Adult leafminer flies are small and black like house flies, with yellow triangles between the wings. Their larvae are yellow maggots that feed inside leaves.
Adult leafminers puncture leaves to feed on sap. The puncture holes turn white and make the foliage look speckled. Larvae damage is more obvious in the form of twisting trails beneath the leaf surface.
Prevention: Remove weeds in the area that may act as hosts to leafminers. Don't overuse nitrogen-based fertilizer since this can attract adult leafminers. Keep your plants healthy with sufficient water and nutrients. The more vigorous the plant, the less leafminer damage. You can also protect young seedlings with protective cloth. However, you can also try for a resistant species to start with.
Control: Assuming your plants are vigorous, they will survive a leafminer attack. When you notice infested leaves, remove and dispose of them. Encourage natural predators like parasitic wasps by avoiding pesticides.
- University of California Integrated Pest Management: Aphids
- University of Connecticut IPM: Biological Control of Aphids
- University of California Integrated Pest Management: Spider Mites
- Clemson Cooperative Extension: IPM for Spider Mites
- Michigan State University: Leafminers
- University of California Integrated Pest Management: Leafminers
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