I found an Asian lady beetle on our sea holly and killed it. Afterwards though I wondered if that was the right thing to do. Is there still hope for the native Ontario ladybug? If so I’ll continue to kill the Asian lady beetle but if there’s no hope for the native ladybug should I let the Asian bug live to eliminate aphids?
Thanks for contacting the Toronto Master Gardeners concerning the Asian lady beetle. I understand the dilemma but killing individual Asian lady beetles is not going to aid the recovery of our native species and you are removing insects that are beneficial in your garden. 179 non-native species of lady beetles (also called ladybugs) have been introduced in North America as biological controls for insect pests affecting the agricultural industry. Nine of these species, including the Asian lady beetle which you have recently seen in your garden have become well established. Asian lady beetles are voracious consumers of aphids and other crop-eating insects, helping to protect home gardens as well as commercial crops. However, the sheer number of these lady beetles suggests they may be contributing to the decline of our native ladybug species by competing for food and through the introduction of diseases. Other possible causes for the decline are the use of pesticides to control the insect species they eat and loss of habitat through urban expansion and loss of farmland.
The Asian Lady Beetle in particular, has increasingly become problematic because they gather in large numbers in the fall (like other species of ladybugs) as they look for safe and dry places to overwinter. They will cluster on buildings and eventually work their way indoors through cracks and openings. They don’t cause damage or harbour disease but are certainly a nuisance. The recommended treatment for any that find their way into your home is to sweep or vacuum them up, seal the bag and dispose of them.
Two of our native species, the Nine-Spotted Lady Beetle and the Transverse Lady Beetle are now classified as endangered in Ontario and thus protected under the Endangered Species Act. As part of the recovery strategy for these species, gardeners/citizen scientists are encouraged to participate in the Lost Lady Bug project and submit a record of any siting’s to repositories such as iNaturalist in order to help determine the location, distribution, and abundance of any remaining populations of these species in Ontario. I’ve included links below to the Lost Ladybug project web site. I’m also including a link to the Species at Risk Ontario site where you can read more about the current state and plans for recovery of our two endangered species.