From time to time gardeners observe outbreaks of pests. There are many choices for managing pests, ranging from a “do-nothing” approach to intensive chemical methods. One method that is quite popular is using biological control, which is using an organism to control the pest in question.
For aphids, this often means employing the help of lady beetles. Lady beetles are predators of aphids both as larvae and adults. The question arises, “How do I get the help of lady beetles in my garden?” One option is to purchase lady beetles and release them in your garden. Another option is to attract native lady beetles and other predatory insects and let them come to the rescue when your plants are in need.
Purchasing lady beetles is not very expensive at around $12 per package from local nurseries, but what are the environmental costs of importing an insect for release into your garden? There could be many, including introduction of a non-native species and disease that could spread to native insects.
Many lady beetles available for purchase are harvested in the wild when the beetles congregate for hibernation in the Sierra Nevada mountains of California. Research has shown that wild-caught insects often carry parasites that may infect other lady beetles. In addition, the commercial harvest techniques may be causing damage to overwintering sites and sensitive ecological areas.
If that information isn’t enough to make you rethink purchasing lady beetles, consider the debate about how effective they are at reducing aphid numbers. Wild-caught lady beetles tend to fly away quickly once released because they have pent-up energy from hibernation and fat stores that make them not as interested in feeding on nearby prey. Because of this, lady beetles may be more suitable for release in enclosed areas, such as greenhouses, rather than an open garden or field.
Other insects are available to purchase that are advertised as being beneficial predators and pollinators, including green lacewings and bumble bees. If you do decide to purchase a beneficial insect, ask the company for information about how the organism was reared or caught. Look for companies that know the species of insect they are carrying and try to find ones that are native to Alaska.
Another option is to make your garden hospitable to beneficial insects, so that when a pest begins to rise in numbers, or your plants need pollination, there are insects nearby to tackle the work. The main thing you can do to encourage beneficial insects is to reduce or eliminate insecticide use in your garden, especially broad-spectrum insecticides that don’t discriminate between friend and foe.
An insect-friendly garden will also have a variety of annual and perennial plants that provide nectar and pollen during the growing season. Consider growing yarrow, alyssum, tundra rose, dill, coriander, angelica, veronica and goldenrod (to name just a few).
Insects need to drink, so make sure you have a water source nearby. This could be a natural pond, an elaborate water feature, or even just a shallow dish with pebbles in the bottom.
Reserve spaces in your garden that do not get tilled or disturbed often as spaces for insects to overwinter. This could be a perennial bed or border.
At this point the jury is still out on whether or not using imported insects in the garden is a sound practice. So when you encounter a pest problem, make a conscious decision about whether purchasing insects is actually necessary for your situation.
Darcy Etcheverry is a program assistant with the University of Alaska Fairbanks Cooperative Extension Service agriculture and pest management program in Fairbanks. She can be reached at 907-474-5107 or firstname.lastname@example.org.