Source: Garden Myths
Ladybugs, which are also called ladybirds and lady beetles are good predators for things like aphids and many people recommend buying them as a natural method of pest control in the garden.
Does this work? Should you buy ladybugs for the garden?
Are Ladybugs Predators?
Ladybugs start life as an egg, which hatches out into a larvae that many would not recognize – see picture below. This larvae is a voracious hunter of insects; they especially like to feed on aphids.
Once they develop into the familiar adult beetle, they continue to hunt and kill pests. Ladybugs are good predators and should be encouraged in the garden.
Are Purchased Ladybugs Native?
There are about 6,000 species of ladybugs. A lot of gardeners in North America know about the local ladybug and the Asian Lady Beetle, but the reality is that there are many “local native” ladybugs.
For example, Ontario has recorded 80 different species including the nine-spotted ladybug (Coccinella novemnotata), the transverse ladybug (Coccinella transversoguttata) and the two-spotted ladybug (Adalia bipunctata).
The most common ladybugs being sold are the convergent ladybird (Hippodamia convergens), which is native to most of North America and the Asian lady beetle (Harmonia axyridis), which is not native in North America. Reliable sources will specify the species being sold, but some sources on sites like Amazon don’t include this information.
Ladybug Collection and Farms
Ladybug larvae eating black aphids, photo source: Gilles San Martin
You might think that these ladybugs are reared in captivity, but that is rarely the case. Most ladybugs on sale are collected from the wild. In North America, California is a common collection site.
There are several problems with the collection of wild beetles. The popularity of purchased lady beetles has skyrocketed and nobody knows what this is doing to local populations. Imagine someone coming into your neighborhood to collect native bees, for shipment across the country.
A second problem has to do with parasites and diseases that are local to the collection area, but which might not be present in your location. Transporting these collected ladybugs could be spreading diseases to local populations including rare local species.
The convergent ladybug is very competitive, and introducing more into your area may have harmful effects on your local species, some of which are already close to extinction.
Are Ladybugs Effective in the Garden?
As soon as you release the ladybugs they will look for food and take care of any aphids you might have. But most backyard gardens can’t support the 1,000 or more ladybugs you bought, so the food source is quickly gone, and they fly away. “About 95 percent of released beetles in research studies flew away within 48 hours. The remainder were gone within 4 or 5 days.”
This predator works better in a closed greenhouse, but in an open yard, they don’t work very well at all.
Do Ladybugs Lay Eggs Once Released?
The beetle does eat aphids, but the adults eat about 1/10 as much as the growing larvae. For ladybugs to be effective they need to lay eggs and start the next generation, and therein lies the problem.
Field-collected lady beetles are usually in a state known as reproductive diapause. They won’t produce eggs until they have been feeding for several weeks and that won’t happen until they fly away from your garden.
Should You Buy Ladybugs?
No, not for your garden. Instead, create a garden that attracts them naturally
How To Attract Ladybugs to Your Garden
Their main food source is aphids, so it is important to allow some aphids to live in the garden. Without a food source they won’t stay.
Different types of laybugs prefer different types of aphids. Some prefer tree aphids, some like rose aphids, and others prefer crucifer (broccoli, cabbage, Brussels sprouts, cauliflower) aphids. A diverse variety of plants is always a good idea.
Ladybugs also eat pollen and nectar, especially early in the year before aphids have hatched out. Some species use pollen as a main food source all summer. The same early flowers that are good for bees are good for ladybugs.
Don’t spray plants for pests. Anything you spray for a pest, also harms beneficial insects. Insecticidal soap and oils are less harmful to lady beetles than pesticides.
Don’t clean up in fall. That leaf litter that looks a bit messy is the perfect place for ladybugs to hide and overwinter. Also, don’t clean up too early in spring or you might move all the hibernating beneficial insects into the compost pile before they can wake up.
What About Ladybug Houses and Feeders?
They don’t work. Don’t waste your time or money on them.