Deb Babcock: The benefits of lady bugs
March 17, 2013
Whitney Cranshaw, one of Colorado's foremost entomologists, or bug experts, was in Routt County in late February to teach the garden insect portion of our local Master Gardening course. Always entertaining, Whitney spent a good portion of the morning discussing lady beetles, one of our favorite garden insects.
About 70 species of lady beetles are native to Colorado, including the Hippodamia, Coccinella, Harmonia, Coleomegilla and Hperaspis genera, which all feed on aphids — the bane of many local gardeners.
The reason we like lady beetles, also called lady bugs, is that they are predators of other insects we don't like. They will eat small insects and insect eggs. And different varieties have preferences for scales, spider mites and mealybugs as well as the aforementioned aphids.
This beneficial insect is easy to identify with its roundish body and bright color — usually red or orange — and spots. There are a couple lady beetle species that are all one color — black or brown — and even one species that is striped.
Lady beetles often produce two or three generations throughout the growing season. They lay eggs in clusters generally near their source of food. If you look closely, you'll often see a mass of lady beetle eggs near a cluster of aphids on a leaf. The eggs hatch in five to seven days, and then the larvae that emerge molt four times, become a pupae before transitioning to the familiar adult form. The larvae is a voracious feeder. One larvae will eat 100 or more aphids in a day as compared to an adult, which eats 20 to 30 aphids per day. We definitely want the eggs to survive! Lady beetles generally live one or two years, at most.
Now, how to get and keep lady beetles in your garden?
There are nurseries and garden catalogs that sell lady beetles that are collected in the wild, often from mountain areas in California. The beetles tend to migrate in certain regions that are well known to collectors when their normal prey no longer is available at lower elevations. Many will go into a state of suspended development called diapause until food supplies return.
The record for buying lady beetles and keeping them in home gardens is poor because lady beetles tend to fly away from the gardens where they have been introduced. And if they were collected in their state of diapause, it will be several weeks before they start laying eggs.
The best thing you can do is to make your garden attractive to lady beetles. And, no, I'm not talking about introducing aphids, scale and mites. The adults also will feed on pollen and nectar in a garden environment when aphids and other prey are not available. They tend to visit plants that have shallow flowers that will be easy for them to reach the nectar. This includes dill, fennel, yarrow, sedum spurge, alyssum, thyme and coriander.
Lady beetles are susceptible to some garden insecticides and you'll kill or drive them away with their use. Certain natural insecticides like neem, Bacillus thuringiensis (or Bt), soaps, horitcultural oils and pyrethrum don't seem to bother the beetles as much.
So if you have problem insects, such as aphids, mites or scale, and have a garden with plants that will sustain lady beetles when other food supplies are low, you'll have a better chance of keeping them around summer after summer.
Deb Babcock is a Master Gardener through the CSU Extension Routt County. Call 970-879-0825 or email firstname.lastname@example.org with questions.