Many insects are present in home gardens and landscapes. Groups like butterflies and moths catch the eye on a regular basis and tend to dazzle us with beauty and grace. Bees, native and domesticated, are noticeable by their buzzing flight and visits to pollinate flowers. Other insect groups have reputations for causing damage or the nuisance behavior they inflict, usually leading to the question of how does one “get rid” of a particular insect. Then there are those groups of insects that remain cryptic and are hardly ever noticed.
Like most organisms in the natural world, all insects have a function and play an important role in the environment. Though many insects bear stigma as pests, most insects serve to benefit and provide ecosystem services. Service oriented insects, along with spiders and predatory mites, are categorized as beneficials. Pollinators tend to be the poster child for beneficial insects, but what about those beneficials that provide pest control services? Before the abundant use of pesticides, beneficials were a primary means of pest control in home gardens and farming communities. Native predator and parasitoid beneficial insects have an estimated value of $4.5 billion annually in the United States and help reduce the application of many chemical pesticides.
Insects Often Become Pests
Why do explosions of insect pests occur in home gardens or landscapes? Why is it that these problems have the potential to be magnified in row crop production systems, commercial fruit production, and greenhouse industries? Many factors are at work, but some locations are just prone to higher levels of particular insects by nature. Certain environmental situations may create increased insect pressure for growing particular plants at those locations. Due to increased industrialization and globalization, many insects have been moved around by the means of importing and exporting goods. This has created new places for insects to thrive in the United States where they once did not. In this situation, if native natural enemies are not present to keep the introduced insect in check, the introduced insect’s numbers can rise uncontrollably and begin to dominate the new niche. This can result in pest-like behavior. The continued use of pesticides to control “pests”, and the general over use of certain pesticides, have in turn created pesticide resistance in many insect groups to certain chemicals as well. However, cultural practices used, or in some cases not used but should be, in gardening, landscaping, row cropping, fruit production, and greenhouses, can determine whether or not pest insects are present and at what levels.
There are a few cultural guidelines used for promoting pest and disease-free gardens and landscapes. Most importantly are those practices used to maintain plant health. This starts from the ground up with proper soil pH, moisture, composition, drainage, and nutrient balance. Healthy plants have difficulty thriving without a proper foundation of good soil and adequate nutrients.
- Soil analysis provides recommendations for addition of soil amendments and proper fertilization methods to enhance plant growth. For more information, see HGIC 1652, Soil Testing
- Selection of healthy pest free plants, either purchased or grown from seed, is a must as well.
- Adopting good sanitation practices that include the removal of diseased plant debris, proper irrigation, and proper fertilization are all important steps towards maintaining plant health and promoting success.
Monitoring and Scouting
Visiting the garden often increases the chances of spotting pest insects before they become a problem. Monitoring a garden or landscape a couple of times a week is a simple way to stay alert to potential insect pests that may harm foliage, flowers, or fruits. Early detection allows for removal of pests by handpicking or pruning out highly infested plant material before populations build further. This reduces the need for chemical control in the long term. Placement of a garden or particular landscape planting in a frequented area makes it simple to monitor in passing. Gardens and landscape areas located out the way may not promote frequent visits, then pests may go unnoticed and populations could build to damaging levels.
Knowing Beneficial Insects
Understanding the role of beneficials in the garden and landscape allows for their use as a biological control tool against pest insects. Familiarity with beneficials, such as who they are, what they consume, were they nest, where they overwinter, or what additional food requirements they need, is useful information for including beneficials into the gardener’s tool kit. Beneficials often already exist in a habitat, but may be present at low numbers. Knowledge of their biology and what makes them tick can assist the gardener in building higher numbers of beneficials to control pest insects.
How does one start to become familiar with beneficials? Defining a few terms is a good place to begin. What constitutes predatory or parasitoid insects, along with spiders and predatory mites? Insects have three distinct body regions (the head, thorax, and abdomen), three pairs of legs, and usually two pairs of wings. Predatory insects hunt, attack, kill, and consume prey. They range in size from barely visible to easy to spot and exhibit generalist to highly-specialized feeding behaviors. Parasitism requires living on or inside another organism, often ultimately killing the organism. Primarily, parasitoid insects lay eggs on or inside the eggs, larva, or adult phase of another insect referred to as the host. Because parasitoids must develop on or within a particular host, they directly target specific pest insects.
Spiders are arthropods (joint-legged animals with exoskeletons) just like insects, but they are not insects. Spiders are categorized as chelicerates (use mouthparts with fangs), have two body segments (a fused head and thorax plus an abdomen) and eight legs. Mites are chelicerates with two body parts and eight legs as well, but are much smaller and more akin to ticks rather than spiders. Predatory mites do not feed on insects or plants, but feed on spider mites and their eggs.
Identification guides often provide colorful photos of many potential pest insects and beneficials to determine which organisms are frequenting gardens and landscapes. After proper identification, it becomes a matter of knowing what types of insects particular beneficials feed upon and the other requirements they need to thrive in order to increase their populations. This information will help gardeners to use them as a pest control tool. Beneficials can be incorporated into various types of integrated pest management and biological control programs, either large or small. For more information see HGIC 1722, Balancing Nature Within Your Landscape.
The table below identifies common types of beneficials and highlights characteristics that can aid in making them a useful arsenal in the garden and landscape.
|Type||Common Prey||Egg-Laying Sites||Shelter/Overwintering Needs||Additional Food Sources|
|Soldier Beetles||aphids, slugs, insect eggs, caterpillars, beetle larvae||in moist soil or leaf litter||overwinter as larvae in leaf litter and loose soil; larvae and adults take shelter underneath rocks, brush piles, decaying wood||pollen, nectar|
|Ground Beetles: Numerous species
Tiger Beetles: Six-spotted Tiger Beetle, Carolina Metallic Tiger Beetle, Eastern Pinebarren Tiger Beetle
|caterpillars, aphids, slugs, beetle larvae, insect eggs||in crevices or soil||overwinter as larvae or adults in grass clumps or dense woody vegetation; adults take shelter under mulch, logs, brush piles, stones||omnivorous: seeds, pollen, detritus|
|Lady Beetles: Multi-colored Asian Spotted Ladybeetle, Twice-stabbed Ladybeetle, Seven-spotted Ladybeetle, Whitefly Predatory Ladybeetle||aphids, scales, whiteflies, mites; some consume eggs or larvae of moths, beetles, flies, thrips||on foliage near prey||overwinter as adults in leaf litter, rock, crevices, under bark, inside buildings; adults take shelter on undisturbed herbaceous and woody plants||pollen, nectar, honeydew|
|Rove Beetles||mites; insect eggs and larvae, slugs||on leaves or under plant debris||overwinter as larvae, pupae, or adults under bark or vegetation; adults and larvae take shelter in leaf litter, grass thatch, logs, brush piles||omnivorous: fungal spores, pollen, decaying organic matter|
|Flower Flies (Hover Flies)||aphids, scales, mites, thrips||on foliage among prey||overwinter as prepupae, pupae, or adults in soil or leaf litter; adults take shelter in field areas with minimal wind||pollen, nectar|
|Minute Pirate Bugs (Orius insidiosus)||thrips, aphids, mites, scales, psyllids, insect eggs, small caterpillars||in plant tissue (leaf blade, petiole) or under bark||overwinter as adults under bark or leaf litter; nymphs and adults may take shelter in plant stems, brush piles, grass thatch||pollen, nectar, plant sap|
|Big-Eyed Bugs (Geocoris spp.)||aphids, scales, spider mites, lace bugs, thrips, whiteflies, small caterpillars, insect eggs||on leaves or in soil/duff near prey||overwinter as adults in low-growing vegetation or under plant debris||nectar, plant sap, seeds|
|Damsel Bugs (Nabis spp.)||aphids, leafhoppers, caterpillars, thrips, mites, insect eggs||in plant tissue (leaf blade, petiole)||overwinter as eggs or adults under leaf litter or grass thatch; nymphs and adults take shelter in crop debris, mulch, brush piles||unknown|
|Predatory Stink Bugs:
Anchor Bug, Spined Soldier Bug, Stilt Bugs
|eggs, larvae, and small adults of a variety of insects||clusters on vegetation||overwinter as eggs attached to plants; overwinter as adults in leaf litter||nectar and possibly some pollen|
Wheel Bug, Red Bull Assassin Bug, Milkweed Assassin Bug, Spined Assassin Bug, Assassin Bug (Pselliopus sp.), Jagged Ambush Bug (Phymata sp.)
|generalists on caterpillars, aphids, leafhoppers, grasshoppers, beetles, wasps, bees, flies, and other beneficial insects||on plant leaves and branches||overwinter as eggs attached to plants; nymphs or adults overwinter under leaf litter, low-growing plants, tree bark||some nectar|
Paper Wasps, Potter Wasp, Great Golden Digger Wasp
|caterpillars, grasshoppers, crickets, beetles, spiders, treehoppers, aphids, true bugs, flies||in solitary or social nests in soil, in wood cavities, nests made form resin/mud/plant material||overwinter as prepupae or adults inside nests, or as mated queens in leaf litter, outbuildings, sheltered areas||nectar|
|Lacewings||aphids, thrips, mealybugs, whiteflies, caterpillars, soft-bodied insects||on foliage near prey||overwinter as prepupae or adults in leaf litter, surface layer soil, crevices, under bark, inside outbuildings; adults take shelter in field areas with minimal wind||pollen, nectar, honeydew|
|Mantids||opportunistic predators on aphids, grasshoppers, beetles, bees, wasps||in groups on plant stems or branches||overwinter as eggs within an egg case attached to plant stems||unknown|
|Parasitoid Wasps: Braconid wasps, Ichneumonid wasp, Eulophid wasps||host specific on caterpillars, grasshoppers, aphids, sawflies, mealybugs, scales, whiteflies, beetles, etc.||on or inside host||overwinter as prepupae, pupae, adults within host, in soil or leaf litter, under bark or protected area; adults prefer sheltered edges with minimal wind||nectar, honeydew|
|Tachinid Flies||generalist parasitoids on many insects; host specific on many caterpillars, grasshoppers, earwigs, sawflies, beetle larvae, true bugs||on, inside or near host||overwinter as larvae or pupae within host; pupae or adults overwinter in leaf litter or soil; adults prefer sheltered edges with minimal wind||nectar, honeydew|
|Spiders: Carolina Wolf Spider, Green Lynx Spider, Bold Jumping Spider||many types of insects and arthropods||in egg sacs on webs, hidden cracks on vegetation or rocks, carried on the female spider||overwinter as eggs or adults in silken nests in soil, grass clumps, plant debris, under bark, inside hollow stalks of vegetation||few consume small amounts of nectar|
|Harvestmen (daddy long-legs)||primarily spider mites, but also other mites, thrips, scales, mealybugs, psocids, whiteflies, small nematodes||in soil or leaf litter||overwinter as eggs in soil or leaf litter||few species omnivorous; scavenge for dead insects|
|Predatory Mites||host specific on caterpillars, grasshoppers, aphids, sawflies, mealybugs, scales, whiteflies, beetles, etc.||on leaves or near prey colonies||overwinter as adults on trees or in soil debris; take shelter in humid microclimates in litter, on plants, trees||few feed on pollen and nectar when no prey present|
Extensive research has been done on potential pests and beneficials in the gardens of South Carolina. For more information, consult the resources below.
- Golden Guides (St. Martin’s Press): Insects by C. Cottam, H.S. Zim, and J.G. Irving (Illustrator)
- Garden Insects of South Carolina by M. Shepard and E. Farnsworth
- Golden Guides (St. Martin’s Press): Spiders & Their Kin by H.W. Levi, L.R. Levi, and N. Strekalovsky (Illustrator)
- Spiders of the Carolinas by L.L. Gaddy