Learn about the good, the bad and the downright creepy to keep your garden safe and thriving.
An orange assassin bug waits for prey.
Did you know that close to a thousand species of insects live in your yard? Good ones and bad, functioning together in a carefully balanced ecosystem. As responsible keepers of our planet, we continually need to make decisions about how to live with both. What follows is not intended as instruction for controlling those invertebrates, but rather a guide to using nature’s ways to maintain the balance.
Whether you call them “insects” or “bugs” (which in some taxonomies are actually a subgroup of insects), of the nearly 100,000 known species, only 600 are considered to be pests. Do you know which are which?
Most beneficial insects are pollinators, predators or parasites. Pollinating insects move pollen between bisexual plants, or within unisexual plants, thereby guaranteeing reproduction. Bees and butterflies are pollinators. Predatory insects eat other insects; spiders immediately come to mind, but they aren’t insects, they’re arachnids. The assassin bug (Reduviidae sp.) is a good example of a predatory insect; fly-eating wasps fall into this category, too. Parasitic insects are really parasitoids because they invariably kill their host. So-called parasitic wasps are included in this category because their larval form lives in, and ultimately consumes, its host. Keeping your landscape healthy requires the presence of these good guys to keep things in balance. If you use insecticides to eradicate the pests, you run the risk of killing the beneficial insects directly, and you destroy the food source for some of them as well.
One of the most voracious predatory insects is the convergent ladybird beetle (Hippodamia convergens), commonly called a “ladybug.” This species consumes huge quantities of aphids, scale insects and mites and is sold commercially for agricultural pest control. Identifying features include two to 13 black spots on red wing covers and a distinctive black and white pattern behind the head. This diminutive insect is not to be confused with the invasive multicolored Asian ladybeetle (Harmonia axyridis), an annoying pest that invades our homes in the fall, littering windowsills and clogging vacuum cleaners. Asian ladybeetles range in color from yellow to orange to red, with up to 19 spots or none – their thorax (body segment behind the head) is also partially white or cream colored. Despite their bad rap-sheet, Asian ladybeetles consume copious quantities of scale insects and aphids, and are responsible for benefiting the pecan industry significantly by eliminating the pecan aphid as well as other insect pests in fruit orchards, tree farms and agricultural crops.
Another insect worth inviting to your garden is the praying mantis (Mantidae). These Transformer-like creatures are a little spooky at mature size (up to 5 inches), but harmless to humans and quite intriguing to watch. Mantids consume many insects, but unfortunately, they are not discriminating and will snare anything that gets close, including butterflies, honeybees, small frogs, snakes and their own kind. The Carolina mantis (Stagmomantis carolina) is the smallest of the group and native to the United States; two imported mantids are also found in most parts of the country – the European mantis (Mantis religiosa) and the Chinese mantis (Tenodera aridifolia), which is also the largest. Chinese mantis egg cases (oothecae) are often sold commercially for biological insect control, but if you look carefully in the fall, you’ll probably find one or two hidden in ornamental grasses or thick shrubs.
Other beneficial insects commonly found in the landscape include all bee-type insects that pollinate flowers, including the aggressive-but-harmless carpenter bee (Xylocopa virginica). Dragonflies are well-known for their diligent pursuit of dinner. Watch for a dragonfly swooping back and forth through your garden; it’s catching hundreds of mosquitoes, midges, gnats and flies. Brilliant green katydids (Amblycorypha longinicta) look very much like grasshoppers. They will occasionally munch on leaves or flower petals, but many of them are predatory and will eat grasshoppers and other destructive insects. Also included in the beneficial insect division are lacewings (Chrysoperla) and the larvae of fireflies (Lampyridae).
Ground beetles and their larvae are some of our best friends in the garden. For example, the fiery searcher (Calosoma scrutator) is an efficient pest eradicator and it’s beautiful to boot. Iridescent green wing covers complement brilliantly the metallic blue, red and purple hues on this insect’s body. A nocturnal feeder (as are most beetles), the fiery searcher climbs trees and shrubs to search out the caterpillars and cutworms that destroy foliage. Beware of touching these beetles, however; their powerful jaws can deliver a painful bite, and the insect’s defense mechanism involves spraying its enemies with a putrid-smelling chemical.
Let’s start with our least favorite July invader: Japanese beetles (Popillia japonica). These little green monsters are known to feed on more than 400 species of broad-leaved plants. Their larvae – also called grubs – destroy lawns and damage the roots of ornamental trees and shrubs. Adult Japanese beetles eat the leaf tissue between the veins, leaving a lacey skeleton that soon crinkles up and dies. An infestation can defoliate a small tree in one day. Adults are oval-shaped, 3/8-inch long and brilliant metallic green, with copper-brown wing covers. Newly emerged beetles resemble adults, but are light brown.
Japanese beetles feed during strong sunlight, preferring to hide on cloudy or windy days. Controlling the pest is a cyclical project, since the grubs can only be destroyed at certain times of the season, and adult females must be stopped before they lay eggs – usually within seven to 10 days after emerging. Experts at Ohio State suggest several methods for controlling these pesky beetles: cultural control with habitat modification; biological control with insect parasites, bacterial milky spore or bug-eating nematodes; mechanical control with trapping; or chemical control with insecticides. Check with your county extension office, or on the Web (OhioLine.OSU.edu/hyg-fact/ 2000/2504.html) for more information.
Everyone knows aphids – those tiny green or black sticky blips on the stems of favored annuals and perennials. Sometimes called “plant lice,” in large numbers these minute sap-sucking insects have the capability to seriously damage or kill plants. Around 250 aphid species are true pests for agriculture and forestry, not to mention the home gardener.
Since well-fed aphids secrete a sweet liquid from their abdomens, the first hint of aphid infestation might come in the form of unusual ant activity around a plant as those highly social insects are known to be aphid farmers. Aphids are especially problematic in areas where their natural predators (ladybeetles, lacewings, damsel bugs and parasitic wasps) have been knocked back by insecticides.
Other bad guys in the garden include earwigs (Forficula auricularia), grasshoppers, squash bugs and stink bugs. These critters will eat their way through your vegetable patch or flower garden in no time. Earwigs are about ½-inch long, flat, dark brown and have sharp “forceps” at the end of the abdomen. Not only do they look villainous, they are. Their favorite diet consists of dahlias, zinnias, lettuce, strawberries, celery, sunflowers, peaches, plums, potatoes, roses, bean seedlings and corn silk. Earwigs prefer cool, damp places, so rather than employ pesticides, trap them by placing newspaper on the soil or in the mulch and gather it up in the morning and dispose of it – preferably by burning.
Grasshoppers cause serious damage to agricultural crops like corn and alfalfa, and when their favorite food becomes scarce, they move on to the residential eateries. One grasshopper can eat its own weight in plant material in 16 hours; if one gets in the house, you can kiss your houseplants goodbye. Natural hopper enemies include birds, rodents, spiders, skunks and several species of parasites – also not welcome in the house. A microbial insecticide is sold under various names for grasshopper control.
Squash bugs (Anasa tristis) and green stink bugs (Acrosternum hiare) are never welcome in the vegetable garden. As their name implies, squash bugs attack cucurbits such as squash, pumpkins and cucumbers. A heavy infestation can destroy an entire vine crop in short order. Green stink bugs prefer your tomatoes, sucking the juice out and leaving white woody patches that eventually decay. Both these insects give off an offensive odor when touched or crushed. Parasitic flies and wasps are the only natural enemies of these two insects.
Depends on how you feel about bugs. Each and every creature in the garden is designed for a specific purpose and often its outer display is less than attractive. A 5-inch praying mantis suddenly leaping onto one’s arm can give a fright and, though spiders are most welcome in my landscape, I don’t appreciate meeting one in the pool – they swim faster than I do.
Identifying insects and arachnids can be entertaining, especially when you discover you have something rare or highly beneficial living in your landscape. Take photos and visit one of several Web sites specializing in insect identification to figure out what you have. My favorites include “What’s That Bug?” at www.WhatsThatBug.com , Master Gardeners at Ohio State Extension ( www.HCS.Ohio-State.edu/mg/manual/ent.htm ), the CSU/Denver County Cooperative Extension Master Gardener at www.CoopExt.ColoState.edu/4dmg/Pests/pests.htm#Insects , and Wikipedia searches for specific insects at en.Wikipedia.org .
Keeping chemical pesticide use to a minimum and providing food and habitat for a host of beneficial insects – regardless of what they look like – can be key to maintaining a pest-free, if not creepy-crawly-free, garden.
When she isn’t writing or taking photographs, Ohio State University Master Gardener Toni Leland tends her acre-and-a-half kingdom in southeast Ohio. Toni writes regular articles for DavesGarden.com, edits and publishes books and video workshops about horses, and is the author of four novels.
More than 150 workshops, great deals from more than 200 exhibitors, off-stage demos, inspirational keynotes, and great food!LEARN MORE