Lady Beetles (Lady Bugs)
One of the most well-known beneficial insects is the ladybug, also called the ladybird beetle or lady beetle. Both the larval and adult stages of this insect feed on destructive pests, including aphids and scale insects.
During its lifetime, including larval and adult stages, one ladybug will consume between 1,000 and 5,000 aphids. Their bright color warns off birds and other predators, letting them know that the ladybug is not a tasty snack. If attacked, the ladybug will exude an unpleasant odor and a foul-tasting substance.
There are thousands of species of ladybugs world wide, and about 400 species in the United States. The majority of them are beneficial, however, each different species has its own feeding habits. The most common ladybug in the United States is the convergent lady beetle (Hippodamia convergens), a medium sized orange ladybug often with five spots on each wing. This variety is the one most commonly sold to gardeners in greenhouses and through the mail.
Ladybugs lay a cluster of 10 to 50 yellow eggs on the underside of leaves close to a food source of aphids, mealybugs or scale insect. The eggs take about seven days to hatch and the larva that emerges is black with orange spots and spines. The larva will actively feed on pests for several weeks before pupating and becoming an adult ladybug. One benefit to the larval stage of ladybugs is that they tend to stay put, while adult ladybugs will often fly away to find a better feeding ground.
Adult ladybugs eat significantly more pests during their lives than the larval stage, but if conditions are not right, they will fly away to someone else's garden. To avoid this, the garden should be made as desirable as possible to the beetles so that they stay at least long enough to lay eggs. Ladybugs that hatch in an area are more likely to stay there.
To attract native ladybugs, plant dill, angelica, wild carrots, and yarrow. Ladybugs are also attracted to grain crops. A spray made from yeast and whey, called wheast, can be purchased to attract ladybugs to the yard. A homemade recipe using one part yeast, one part sugar, and enough water to mix into a thin paste, can also be used. The mixture can then be applied with a spray bottle to plants. This mixture will attract the ladybugs and it is thought that it also encourages them to stay and lay eggs.
Ladybugs can be purchased at many garden centers and online. Many of the ladybugs available for purchase are collected in the mountains of California, where they converge by the millions. When purchasing ladybugs, the best choice is to buy beetles that were collected in the spring rather than those collected in the winter. Winter collected beetles tend to fly away from the area they were released in greater numbers than spring collected beetles. However, spring collected beetles tend to eat fewer pests. They do stick around to reproduce, however, and are a better choice for long term pest control.
To increase the likelihood that purchased beetles stay in the yard where they are released, the best practice is to release them at dusk and spray down the garden with water right before release.
There are some species of ladybugs that are not beneficial and can even be considered pests themselves. The most common of these is the Asian lady beetle. The Asian lady beetle can be distinguished from other ladybug species by the large white spots on the side of its head with a distinctive black M shape between the spots. These beetles tend to congregate in homes, leaving a sticky residue on carpets, furniture and walls.
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Beneficial Insects 101: Ladybugs
University of Kentucky Entomology: Ladybugs
Ohio State University Extension Fact Sheet: Lady Beetle