Experts agree that only a very small percentage of the insects and spiders in our yards and gardens are actually pests, feeding on our desirable vegetation or infecting it with plant diseases. Indeed, many insects are helpful partners in our gardens, devouring aphids and other plant-eating pests. Pollinators like honeybees and butterflies are essential participants in the reproduction of many flowers, fruits, and vegetables. Some small, stingless wasps or flies assist us by laying their parasitizing young on or inside doomed pests. Although beneficial insects won’t keep our yards pest-free, their contributions should not be underestimated.
Biological Control: A Guide to Natural Enemies in North America, Cornell University
IPM Online, University of California
Helping beneficial insects feel at home
As a gardener, there are things you can do to help sustain natural populations of beneficial insects:
Provide their preferred and alternative foods – Scatter a wide assortment of flowering plants throughout your garden and landscape or cluster them in a designated bed or border. Because different beneficial insects use pollen and nectar at different times, choose diverse plants with long, overlapping bloom periods. Pollinators aren’t the only beneficials that rely on flowering plants. Nectar can help parasitoids (insects that develop in or on another insect pest) span periods when hosts are few. Nectar, pollen, and plant juices can also help predators (insects such as ladybird beetle larvae, above, that consume other harmful insects) survive times when prey numbers are low.
Provide shelter – Beneficial insects need protection from predators and human disturbances. These beneficial insects can find cover in perennial flower beds, hedgerows, cover crops, and mulches.
Provide water - Bird baths, shallow containers, or temporary puddles, with sticks or rocks for perching, can help beneficial insects through dry periods. Change the water every two or three days to discourage mosquito breeding.
Protect them from insecticides - Broad-spectrum insecticides kill beneficial insects right along with pests. To minimize impacts on beneficial insects, choose chemicals that are less toxic and more specific. Consider these environmentally “softer” alternatives: insecticidal soaps, horticultural oils, botanicals, Bacillus thuringiensis (Bt), and insecticidal products that act specifically as stomach poisons to foliage-feeding pests.