Identifying and Dealing with Problem Insects
Locate the Suspect
Start by inspecting your plants closely. Look for the culprits under leaves and between plant stalks. Many pests stay on the plant at all times, and a close and thorough look will reveal the source of the problem. Other pests run or fly when disturbed, so you may need to "sneak up" on them. For instance, if you see a cloud of tiny, pale moth-like bodies fluttering above your plant, you may have a whitefly infestation. Some pests come out at night to feed, so you may need to check after dark using a flashlight. Snails and slugs, for example, tend to do much of their foraging in the cool and damp of the evening.
Once you've found the pests, then next step is do identify whether you have the "chewing" or "sucking" variety. This is critical since the specific steps you take in controlling and treating for insect pests are determined by the particular types that are attacking your plants.
Varieties of Pest: Chewing Types
You likely have this type if your plants have leaves that are half-eaten--perhaps with foliage that looks like a "leaf skeleton." Chewing insects tend to eat on the leaf material between the veins. Distinct holes in the leaves also indicate the presence of chewing pests.
Common chewing pests include:
Snails and slugs are one of the most common garden pests. They typically start eating from the outer edge of leaf. They prefer to stay where it's dark and cool, so inspect the underside of leaves for snails, slugs or the tell-tale silvery trail of "slime" they leave behind.
Earwigs, in their adult form, are the familiar "pinching" beetle. They eat both plant and animal matter and, in particular, are known to target Dahlias, Zinnias, marigolds, roses, lettuce and strawberries.
Caterpillars, cutworms and hornworms are among the most damaging of the chewing pest variety. They may chew into the plant's stem at ground level. One indicator that you have caterpillars or cutworms is the waste they leave behind in the form of black or green pellets.
Varieties of Pest: Sucking Types
These types pierce the surface of the leaf or stem and suck nutrients out of the plant. Indicators of the sucking variety of pests include discolored, mottled, twisted or curled foliage.
Common sucking pests include:
Aphids are small, winged insects. They particularly like new plant growth.
Whiteflies are a small white insect--not a true fly, but actually a relative of the aphid. They're frequently found on the undersides of leaves.
Tips for Controlling Slugs and Snails
Remove excess moisture.
Snails and slugs are attracted to the yeasty odor of beer. Put out a shallow dish of beer overnight. Slugs will crawl into it and drown.
Consider "slug-resistant" plants. Some popular backyard plants that are resistant to snails and slugs include Begonias, Fuchsias, Geraniums, Impatiens and nasturtiums.
Try using copper tape (available from nurseries and garden centers) to protect trees and plants from slugs and snails.
Tips for Controlling Aphids
One of the simplest methods for removing aphids from plants is to use a strong stream of water from a hose and sprayer attachment to knock them off leaves.
You can create your own aphid deterrent by using one tablespoon dishwashing liquid to a gallon of water. Spray the solution onto the leaves.
Release lady bugs or praying mantis. Both of these insect species are beneficial to gardeners since they are predatory species and feed on other insects--including pest species.
Tips for Controlling Caterpillars
Homemade garlic and pepper sprays protect against cabbageworms, caterpillars, horn worms, aphids and flea beetles. Use 6 cloves garlic, 1 tbsp dried hot pepper, 1 minced onion, 1 tsp pure soap and one gallon of hot water. Spray the solution onto the leaves.
Release praying mantis.
Other commercial products for controlling pests include insect netting and insecticidal soaps and oils
Sprinkle ground hot pepper directly onto leaves to deter chewing pests.
Know what bugs you're dealing with. When in doubt, take a leaf to a specialist. Check with your local nursery or agricultural extension.