We’ve been writing a lot of blogs about garden pests and problems—so let’s do one more! This summer, mealybugs have been an issue for many of our readers and other gardeners around the United States. They’re a perennial problem in many places, and treating them requires a bit of understanding about what these creatures are and how they interact with our plants. Mealybugs are surprisingly complex and dare we say interesting little critters, and they’re worth exploring a bit about in their own right. So let’s dig in and learn a bit more about mealybugs and what to do about them.
Gardzen Executive Summary
· Mealybugs are scale insects, members of the family Pseudococcidae.
· The female mealybug has a waxy outer layer and looks likes a small scale or waxy flake on the stems and leaves of an infested plant.
· Mealybugs feed by sucking fluids out of the plant, which weakens it.
· Mealybugs also serve as a vector for plant diseases and infections.
· Mealybugs infest a wide variety of popular garden plants and crops
· While mealybugs are difficult to control with pesticides, there are a number of other insects that feed on them. Biological controls like this can be effective against mealybugs.
· Preventing mealybugs from spreading into our garden spaces is the best way to keep them away from our plants.
First, What Are Mealybugs?
Mealybugs are a collection of different species that are in fact, bugs—specifically they’re insects from the family Pseudococcidae, also called scale insects. The moniker “scale” comes from the sexual dimorphism displayed by these insects: while the male scale insects look more like, well, insects, with wings and legs and antennae, the females look like small waxy scales on the stems and leaves of plants.
The way these bugs live on plants is the problem. Mealybugs, like other scale insects, are herbivores and feed by sucking liquids from the plants they inhabit. The scale-like females then secrete a waste product called honeydew, which is sugar-rich and sweet-tasting. This leads to one of the most interesting things about mealybugs: their occasional symbiotic relationship with ants. Some ants will protect and care for mealybugs and other scale insects so that they can feed on the honeydew they produce. Honeydew, which again is rich in sugars, is nearly the perfect food for an ant colony.
How Mealybugs Harm Plants
All that sugar is also the perfect food for some other things, namely various kinds of mold and mildew that cause serious health problems for the plants upon which mealybugs feed. Coupled with the fact that mealybugs also provide a vector for other plant infections and illnesses, it’s easy to see how these interesting little creatures can become serious problems for gardeners, farmers, and horticulturalists.
It gets worse when we learn that mealybugs often infest some of our most popular crops and garden plants. This is only a partial list, so as always we encourage you to consult with your local cooperative extension or garden club and learn what insects are problematic in your particular area or region:
· Grapes
· Citrus plants—oranges, lemons, limes, grapefruit, and other popular species
· Coffee trees
· Sugarcane
· Mulberries
· Sunflowers
· Cacti and some succulents
· Tropical fruits like bananas, papayas, pineapple, and guava
· Decorative plants like ferns, gardenia, hibiscus, and coleus
These are are popular food plants, decorative plants, and plants that provide significant income for farmers and orchard-keepers. You can see how mealybugs can be a serious problem for them if they start spreading disease. Mealybugs can be difficult to control, but there are some options we can employ to help keep them from infesting our garden spaces.
What Can We Do About Mealybugs in Our Gardens?
As with most garden pests, the best first step is prevention. We can help prevent the spread of mealybugs by buying plants and garden supplies from reputable sources and then inspecting them for signs of mealybugs or other unwanted visitors. Mealybugs are nothing if not visually distinctive, so we can often spot them or their eggs during a careful search.
If despite our best efforts mealybugs find their way to our gardens, we still have some options. While mealybugs are difficult to control chemically in part due to the females’ waxy outer coating, they are vulnerable to many natural predators that we might welcome into our garden. Ladybugs, lacewings, and spiders are all welcome garden visitors who can help control mealybugs. Even more effective is the wonderfully named mealybug destroyer lady beetle, Cryptolaemus montrouzieri, a carnivorous insect that preys heavily upon mealybugs. Gardeners and farmers in regions prone to mealybugs often introduce the mealybug destroyer lady beetle into their gardens to help eliminate or control mealybugs.
In addition to biological controls, smaller garden spaces can rely on manual removal—picking the bugs and their eggs off the plants or removing heavily infected plants. Both should be disposed of in a sealed container like a plastic bag so that they can’t escape and spread further. As always, dispose of infected or infested plant matter in the trash, not in the compost heap!
There are many different species of mealybug, more than we can cover individually in a single blog. We strongly encourage everyone to find out what works best in their region—again, your local cooperative extension may be able to help.
No Bad Plants, No Bad Bugs
We stand by our statement: there are no bad plants, just plants growing where we don’t want them. Likewise, there are no “bad” bugs, just species that have been introduced to a space in which they inadvertently cause problems. Mealybugs are a problem for farmers and gardeners, and we should all do our best to help control their spread. However it’s also important to remember that no life form is innately “bad”. They cause us problems but they do so without malice and we should treat them as such. Biological controls and inspections to prevent their spread are the best ways to control mealybugs and the damage they cause. Manual removal and careful disposal are the next step when needed.
We hope this blog clears up some of the frustration and mystery around mealybugs and other scale insects and helps you control them if they should appear. If you have direct experience with mealybugs and know some tricks for controlling them, we’d love to hear from you so please get in touch via email or in the comments. Gardzen is all about community—and we’re glad you’re part of it!
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