Most people think only of pests when they think of insects. But, the beneficial insects found in gardens do not feed on or harm plants. The typical backyard contains hundreds of species of insects, yet only a fraction can even be observed because many are microscopic and/or hidden below ground or within plant tissue. Most are just “passing through” or have very innocuous habits. Others actually feed on and destroy pest species, while others help decompose plant and animal matter, or act as plant pollinators.
Beneficial insects can be categorized broadly as either predators or parasites. During development in both adult and immature stages, predators actively search out and consume their prey, while insect parasites develop in or on a single host from eggs or larvae deposited by the adult. Predatory insects include different species of flies (Hover, Syrphid), bugs (Damsel, Bigeyed, Minute Pirate, Assassin Bug, Spined Shoulder), beetles (Lady, Collops, Ground), Lacewings (Green and Brown), Cicada Killers, Paper Wasps, Spiders (not insects, but still important predators), and the ever popular Preying Mantis. As for Parasites, they include Tachinid flies and Parasitic wasps.
Conservation is key in retaining these pest warriors in your garden and landscape. There are three things you can do to help them help you. First, reduce or stop the use of insecticides, as most are broad spectrum, killing beneficial insects as well as target pests. A few insecticides, such as Bacillus thuringiensis (Bt), are not toxic to predators and parasites. Where possible, use a systemic insecticide which penetrates the plant and has less contact toxicity. Second, protect beneficials from environmental extremes by providing them a space where temperature, humidity, and light intensity are optimal for survival.
Plants with a dense canopy, such as small trees, shrubs, bushy perennials, and tall ornamental grasses, provide shade as well as nesting sites to enhance reproduction. These plants also can be ideal for ambush predators such as predatory bugs and some spiders. And, don’t forget about organic mulches and ground cover plants as they can support greater numbers of ground-dwelling predators than bare soil. Finally, provide beneficials with food resources necessary for their survival and reproduction. Flowering plants rich in pollen and nectar will attract adult predators that feed on these important energy sources.
It is important to recognize the valuable role that these beneficial insects play so they can be appreciated and encouraged to live in your garden. So, get out there as a garden detective and investigate the world of beneficial insects, for they are truly the good guys.