There are three kinds of garden insect pests: “suckers,” “borers” and “chewers.” Sucking insect pests like aphids suck sap from your plants and some may spread disease. Boring insects have strong jaws to bore beneath tree bark and into stems. Examples are wood boring beetles. Chewing insects like caterpillars eat your plants and don’t leave much behind.
Identify the Insect Pest
To identify an insect pest, take a sample to a local nursery or a Cooperative Extension Office/Master Gardener Program. If you don’t have access to either, try looking up the insect pest by description on www.bugguide.net or send me a few good photos at firstname.lastname@example.org
In some cases you may find pest damage but not the culprit. To catch insects in the act, sneak outside at night with a flashlight and investigate. During the day, crouch near the damaged plant and look for signs of movement or insect droppings.
If plants are sticky to the touch and/or you find ants crawling on your plants, your pest is a “sucker.” Aphids, scale, mealybugs and whiteflies suck plant juices and leave behind a sweet, sticky substance called “honeydew.” Ants protect the insects from predators and feed on the sticky honeydew. Some suckers, like scale may escape notice because they are often flat or very small. To find out how to get rid of these pests, read Eco Gardening: Pesticides.
I must take a moment to mention this tiny but worthy garden adversary. Even if you have a healthy balance of predators and prey in your garden, aphids can be a problem in early spring. Keep an eye on this pest and use a gentle stream of water to knock them off and kill them. Learn why aphid populations explode in this mini video. https://www.youtube.com/watch?v=xZvGXdyC5lc
Boring Insect Pests
If the symptoms of a problem are small holes in twigs or branches, you may have a boring insect. (their larva are often “chewers.” These critters are harder to catch as by the time you find the hole they may already have hatched and left. Common boring insects include some types of beetles, sawflies and carpenter bees (the latter is harmless and can be prevented by painting wooden structures). Termites are another kind of boring insect. In most cases the best way to prevent boring insects is to prune off infected plants as soon as you see the damage and get rid of the plant waste.
Chewing Insect Pests
If plant damage includes missing parts of leaves, stems or entire plants demolished, you probably have a chewing insect pest. Chewing insects can be earwigs, caterpillars, grasshoppers and snails and slugs. (Snails and slugs are actually animals/mollusks, not insects).
Sometimes in the leaves of roses and leaves flowers of bougainvillea (and various other plants) may have “scalloped” leaf damage. These perfectly notched missing pieces are used by leaf-cutting bees which use them to build nests. The damage is usually not enough to harm your plants. Also, bees and other pollinators are in short supply these days, so you avoid doing anything that will further damage their populations.
It’s important to remember that insect pests are part of the “food web.” This means it’s necessary to have some present in your garden for beneficial insects and animals to eat. If you spot one grasshopper or a few aphids in your garden, it’s not a pest problem. But when pest populations begin to decimate your plants, you’ll want to take action.
Many times plants damaged by insects are already unhealthy plants susceptible to attack. To keep plants healthy, water them deeply. This ensures they have a vigorous sap flow that can help prevent most insect attacks. Read more about deep watering in Gardening 101: Watering.
To prevent insect populations from reaching high levels, check plants frequently for signs of invaders. Identify the pest and spray them off with water or handpick and/or knock them into jars of soapy water. For more information on safer alternatives, read Eco Gardening: Pesticides.