Ask a Master Gardener

Lady Beetles

4/6/21

I really love ladybugs and I’ve heard they are good for your garden. Is that true? JG

Ladybugs have to be one of our favorite garden visitors: right up there with butterflies and bees. Technically, ladybugs are called lady beetles or ladybirds although I don’t remember the last time, I heard someone call them ladybirds. Even though there are approximately 450 varieties of lady beetles in North America, the one we are probably most familiar with is the convergent lady beetle aka Hippodamia convergens Guérin-Méneville, but let’s just stick with lady beetle.

The good news is that lady beetles are great for your garden since both the adult and grub-stage larvae are voracious predators of other insects. While they have a wide variety of insects they will dine upon, the one we are perhaps most familiar with is the aphid. An adult lady beetle can eat up to 50 aphids a day, which is good due to the rate at which aphids can reproduce.

The larvae of lady beetles are strictly predators while the adult lady beetles might supplement their diet by dining on pollen, nectar, or even honeydew (poop from certain insects like aphids).

Lady beetles reproduce by what we call “complete metamorphosis” which differs from the “incomplete metamorphosis” of say a grasshopper. Grasshoppers are born basically small little grasshoppers which grow into adult grasshoppers through several growth stages we call instars. However, lady beetles (like many insects) start as an egg, become a larvae, molt 4 times as they are developing, move on the pupae stage, and then on to their final adult form.

Their orange eggs are usually deposited on leaves in clusters near a food source like aphids. They remain in the egg stage for 5 to 7 days before becoming a larva. Lady beetle larvae do not look much like an adult lady beetle and quite frankly look more like the predators they truly are.

These larval lady beetles go through 3 development stages (instars) over the course of about 2 weeks. At the end of this feeding stage, the lady beetle larvae attach themselves to a surface by their backside. Interestingly, they remain in this prepupa stage for two days before molting into the full pupal stage. Although they are attached and relatively motionless during this stage, oftentimes they will react or move a bit if disturbed. This pupal stage typically takes 5 to 8 days. When the adult emerges, they are a little light in color, but the wings darken and harden over the course of a couple of days. This life cycle can repeat 2-3 time per year.

At the end of the season when it starts to get cooler, lady beetles begin to search out a protected location to overwinter. Typically, these winter homes are beneath plant debris or behind bark flaps of trees. The fact that they overwinter in plant debris is a good reason to leave the leaves etc. in your garden during the winter and then clean up in the spring when it begins to warm up. While they are overwintering, development ceases in a condition known as diapause.

While many garden centers sell lady beetles during the growing season as a natural method of pest control, there are pros and cons to this strategy. Yes, releasing lady beetles is a natural way to try to control aphids. But unfortunately, there’s no guarantee they will stay in your yard after being released because lady beetles are highly dispersive. Some will likely remain but expect the majority of your guests to fly off to points unknown.

A better strategy would be to populate your garden with flowers that will naturally attract lady beetles. Since their primary motivator is to find a food source for themselves and their young, if you have aphids, they will likely find your garden. This doesn’t mean you shouldn’t purchase lady beetles for pest control, but it does mean you should lower your expectation of these purchased lady beetles doing exactly what you want them to do.

Since lady beetles will also feed on other food such as nectar and pollen, having a good source of these will make your garden more desirable for lady beetles. Flowers that would be appropriate would be shallow flowers with nectar that is readily accessible by their mouthparts such as alyssum, coriander, or dill.

Another good way to help the lady beetles in their search for aphids is to minimize ants as best you can. Aphids excrete honeydew and honeydew is a favorite food for ants. When ants are after honeydew, they tend to drive other insects away from their food source. Any ant treatments should go on the soil below the plant rather than on the plant itself.

And if you want to attract and keep lady beetles in your garden, you should work to minimize your use of pesticides. If a pesticide is needed, try to use the more targeted, organic pesticides such as insecticidal soap or neem oil. But be sure to spray these only on the pests you are trying to get rid of and apply in a way that is consistent with their instructions.

Ultimately, lady beetles are a welcome resident in healthy flower and vegetable gardens. Good luck.

You can get answers to all your gardening questions by calling the Tulsa Master Gardeners Help Line at 918-746-3701, dropping by our Diagnostic Center at 4116 E. 15th Street, or by emailing us at mg@tulsamastergardeners.org.

Photo: Russ Ottens, University of Georgia, Bugwood.org