Polished lady beetle. © Beatriz Moisset. 2012
Seven-spotted Lady Beetle (Coccinella septempunctata). © Beatriz Moisset. 2013
Now that we settled this, we can move on. If you are thinking of just one generic lady beetle, think again. The 500 species of lady beetles in North America vary in size from a pinhead to almost half an inch. They are not all red with black dots; some are entirely black or mostly red or have a pattern of black and ochre or black and yellow.
Most feed on aphids and other small, juicy insects, and we love them for that. But a few of them feed on plants, to gardeners’ disappointment. A handful of species feed on mildew. The babies, or larvae, are as ugly as the adult is pretty (well, I find them beautiful anyway). They look like little alligators. If all this shocks you a little, you may want to spend a couple of minutes digesting it.
Most of those
500 species of lady beetles are native to North America; but a few
dozens came from other continents. Some arrived accidentally, but
others were brought to combat pests. The first one of these
intentionally-introduced pest enemies was the Vedalia beetle, Rodolia
cardinalis, brought from Australia in the 1880s to fight a
non-native pest, the cottony cushion scale. This scale insect was
devastating the orange groves of California.
|Spotted lady beetle larva (Coleomegilla maculata). © Beatriz Moisset. 2013|
The introduced lady beetle was such a resounding success that it inspired horticulturists to start using other insects as pest controls, also called biocontrols. Some of the newcomers are doing a satisfactory job, especially the ones that help control non-native green-house pests. It is too bad that sometimes we learn the hard way about unintended consequences. Not all introduced species continue to be well behaved guests. Some develop into unwanted pests themselves.
You will not like what I am about to tell you because I am sure you have seen this lady beetle and delighted in it, thinking that it is a good friend of your garden. The Asian lady beetle, Harmonia axyridis, has been in North America for almost a century. It was brought from Asia because of its voracious appetite for aphids. We can’t deny that it goes through them with gusto.
Asian lady beetle invasion in winter. © Beatriz Moisset. 2009
The concept of using lady beetles has spread to ordinary gardeners, who see advertisements and decide to purchase some. This is not as desirable as it seems at first sight. You can find some good advice at the North Carolina State University website, University of Wisconsin website and About.com.. Purchasing lady beetles may be unnecessary if you maintain a healthy garden (no pesticides) which invites the local lady beetle fauna. Moreover, a healthy garden welcomes other allies in the war against aphids, such as lacewings, syrphid flies and parasitic wasps.
If you still insist on buying lady beetles, beware! Most sites that sell them provide insufficient or false information. Some don’t mention which species they are selling, as if all lady beetles were the same. They are not! They fail to inform you where they were collected, or whether they were bred. A few provide the wrong instructions for releasing them.
Convergent Lady Beetle (Hippodamia convergens). © Beatriz Moisset. 2013
Eggs of unidentified lady beetle amidst a colony of aphids, also a beautiful sight. © Beatriz Moisset. 2013
© 2014, Beatriz Moisset. First published in Native Plants and Wildlife Gardens.