Guest Blog provided by UNH Cooperative Extension’s Education Center
Insects, spiders, predatory mites, and other arthropods are considered beneficial when they eat arthropods that humans consider undesirable. Few arthropods are actually pests; of all insect species, over 97 percent of those usually seen in the home landscape are either beneficial or are “innocent bystanders.” Managing our yards as habitat for beneficial arthropods—commonly called “natural enemies” or “beneficials”—is a great way to minimize pest problems, often greatly reducing or eliminating pesticides. This fact sheet describes a long-term, systems-wide approach to manage arthropod pests.
Spiders: All spiders are predators, and most feed on insects caught in a web. Others, such as jumping spiders and wolf spiders, are active hunters relying on excellent vision to kill their prey. Crab spiders, another commonly encountered group, ambush their prey. A recent study1 indicates that spiders are often the most abundant predators, as a group, on a wide range of plant material in the home landscape.
Green and brown lacewings: Green lacewing larvae are called “aphid lions” for good reason; they attack and consume large numbers of aphids, mites, lace bugs, and other small insects. Pollen, nectar and even honeydew sustain the generally nonpredaceous adults. Green lacewing larvae can be purchased commercially and offer a safe, though sometimes costly, nonchemical alternative for controlling aphids and lace bugs.
Lady beetles: Both the larvae and adult lady beetles are voracious predators that can eat hundreds of aphids in their lifetime. They also eat insect eggs, mealybugs, and other soft-bodied insects and mites. Some species of lady beetles have favorite prey, as indicated by the names given to the “mealybug destroyer” and the “spider mite destroyer.” Flowering, pollen-producing plants in the landscape attract lady beetles.
Ground beetle: One Calosoma sycophanta larva can consume 50 large gypsy moth caterpillars in two weeks, while a pair of adults can devour over 300 gypsy moth caterpillars and pupae per year. Ground beetles typically have one generation per year, and some adults can live for two to four years.
Praying mantids: Because these insects feed on anything they can catch, including honey bees, each other, and other beneficial insects, their value in reducing the numbers of key pests in the garden and landscape is questionable. Contrary to popular belief, they are not protected by any state or federal laws.
Hover flies (syrphid flies or flower flies):The larvae are valuable aphid and adelgid predators, capable of consuming over 400 aphids before pupating. Providing food for the nectar- and pollen-feeding adults by planting flowers will encourage them to lay eggs in the landscape or garden. Hover flies are excellent at detecting and attacking even low numbers of aphids.
This is just a small sample of the beneficials that help control pests in your home landscape.
Attracting and Sustaining “Good Bugs”
Develop a tolerance for some damage by arthropods to your plants; many plants can tolerate low levels of pest damage with few ill effects.
Provide shelter. Leaving some leaf litter and debris under shrubs may provide beneficial arthropods a place to hide during adverse conditions such as hot summer days.
Increase the diversity of your landscape. Grow a wide assortment of plants to create habitat for a wide range of natural enemies. Also, diverse plantings of the right species that are pest and disease resistant make it less likely that pests will cause problems.
Do not use zapper lights that electrocute insects. In study at the University of Delaware, these lights killed many more beneficial insects than pests.
Ensure a continuous supply of floral nectar and pollen by selecting plants with a succession of flowering times. Nectar is an important source of carbohydrates that provide energy; pollen is a protein source. Because the appetites of beneficials may peak before your garden does, plant an early bloomer, such as sweet alyssum or pansy. Include late-blooming plants such as goldenrod and aster species, many of which colonize areas on their own.
Choose their favorite plants. Many beneficials like tiny flowers that offer both pollen and nectar.
To learn more about creating and enhancing wildlife habitat on your property, order any or all of our other Habitats fact sheets. See the University of Maine Cooperative Extension Online Publications Catalog for the complete Habitats fact sheet series.
To learn more about managing arthropods and plant diseases, see our online pest management fact sheets and our Home and Garden IPM (Integrated Pest Management) website at https://extension.umaine.edu/ipm/, or call 1-800-287-0279 (in Maine) or your UMaine Extension county office.