Mealy bugs.
Are.
The.
Absolute.
Worst.
Maybe second to spider mites, but not by much. If you only grow outdoor plants, you probably have a burning hatred for these just as much as indoor plant growers hate spider mites.
Fortunately, they’re much easier to deal with than spider mites, at least if you’re diligent. Nearly everyone gets mealies at some point, particularly if you bring home nursery plants or plants from big box stores. While getting the occasional bout of mealy bugs is extremely common, they can rapidly go from a manageable treatment to decimating your collection if you’re not careful.
What is a Mealy Bug?
There are actually multiple species of mealy bug, all in the family Pseudococcidae. The ones you’re most likely to see are either the Obscure Mealy Bug, Pseudococcus affinis, or the Citrus Mealy Bug, Planococcus citri. There are numerous other species, but the general treatment and appearance is the same.
They’re almost all small, segmented little bugs that bear a passing resemblence to soft looking roly polies. Usually, they’re a bit fuzzy or waxy looking, and will lay eggs in cottony looking egg sacs. Mealybugs will eat plant sap and excrete “honeydew” and wax, causing a distinctive buildup that is easily recognizable on more infested plants.
Due to the excretion of honeydew, ants will common bring mealy bugs into areas that they weren’t found previously, so keep an eye on any ant infestations around your plants.
Spotting Mealy Bugs
The first sign of a mealybug infestation is often plants that don’t quite seem to be thriving, or have discoloration that can’t be readily explained by watering habits or sun exposure. You may also see the little egg sacs, which look like little white fuzzy ovals.
At right is my Aeonium “Mardi Gras”, a succulent that normally goes dormant in summer and looks a bit raggedy no matter what during this time of year.
But if you look closely, you can see that it’s a bit…off.
The leaves are coming in a bit funky in shape, and there’s weird ragged sides as well as pock marks and imperfect leaves even where it’s grown in new after our hail storm.
This plant is also kept on our concrete patio, next to an area where we have a persistent ant problem, and whenever I’d water this plant I’d see ants coming out of the pot. Ants moving into pots is also a strong sign of a probable mealy bug infestation.
When I checked closely, I was able to spot the tell-tale wax and dirt left behind from mealybugs.
Since I use the spray setting on my hose attachment, it appears that I’ve been blasting them off and they’re not able to get a strong foothold…but they’re still there.
In Aeoniums like this one, mealy bugs are most often spotted close to the stem in older leaves, right near the center of the rosette. If you’re seeing them in the very middle of the rosette, that is a strong sign that your infestation is quite bad and they’ve maxed out space in less visible parts of the plant.
Mealy bugs really like being close to the juicy plant stem, and in most rosette-forming succulents, you’ll find them in similar places.
I had this Dudleya next to the Aeonium above (as you can guess, also in easy reach of ants). It was a beautiful, robust speciment with white farina-coated leaves, but slowly started to get sadder and sadder as I had it.
While Dudleyas, like Aeoniums, go dormant in summer, this was not the usual summer die back.
If you look closely, you can see spotting and that the inner leaves don’t look quite right. You should also be able to see some mealybug dirt just to the bottom left of the center of the plant.
The Dudleya has a layer of farina, and that powdery coating seemed to be working in the mealy bugs’ favor, keeping them protected from water washing them away.
At left is what it looks like when the honeydew secreted by the mealies starts to develop black sooty mold, a secondary and nasty effect from the infection.
I’d already sprayed this dudleya with pesticide to treat the mealies once, and will need to again – but there are few if any actual mealy bugs visible here. This is just what they’ve left behind and is relatively easy to wash away if you know where to spray.
Another plant from that poor patio placement is my cluster of Echinopsis “Rose Quartz” cluster, which I’ve had for nearly 5 years now.
The side facing out towards the patio (and the sun) looked fine, but as I was moving plants around and checking what was left on the patio, I discovered the mealies had set up a buffet on the shaded side of the cactus.
At right is what the distinctive egg sacs look like, which can either hide a female laying eggs, juveniles, or just the egg sacs.
For any plants you have that are similarly exposed to harsh sunlight on only one side, make sure to check all sides at least occasionally! This happened to my Echinopsis in the space of about 2 months, and it’s definitely the most infested plant from the patio.
Mealy bugs also REALLY love to hide out in cactus fuzz.
If you have a cactus with a fuzzy crown, check the fuzz closely on a regular basis. I am fond of copying @cactusupdate and using a paintbrush to gently brush the fuzz on my cacti and use that as an opportunity to look for signs of mealies.
For my Coryphantha andrae at right, even the occasional brushing took me quite a while to discover the infestation hiding in the cactus’ crown. My first sign on this one was yellowing on top of the spine tubercules, and then on closer inspection, discovering mealy bug poop.
Some careful inspection with dull tip tweezers led to discovering nests of mealy bugs hiding in the fuzz of the crown of the cactus.
I was able to grab one large one with the tweezers, visible left.
In the fuzzy crowns of plants, they are particularly hard to spot, so diligence over any plants that don’t look quite right is essential.
How to Treat Mealy Bugs
There are a ton of ways to treat mealy bugs, ranging from natural methods to heavy uses of pesticides. What works best for you in the short and long term is something you’ll have to decide on your own.
Natural control
One way to try and control mealy bugs is with natural mealy bug predators, such as lacewing larvae, ladybugs, and a relative of the ladybug called “the Mealy Bug Destroyer” (an Australian relative of the US ladybug).
Any and all of these can help keep mealy bugs under control, but are unlikely to completely eliminate them due to the natural balance predators and prey tend to strike. If you’re growing indoors, at least two rounds of releasing mealy bug predators should be done, preferably 3 over the course of 2 months, which should catch the mealies at pretty much all stages of development.
Outdoors, these predators are a better holistic and long term choice. All three predator types will cover (relatively) large distances, particularly compared to slow moving mealy bugs, and can easily eat hundreds of mealy bug larvae each. Periodically releasing predators into your outdoor greenhouse, yard, or simply by your plant shelf can be a useful way to keep your outdoor plants safe.
It’s not perfect, however, as my plants above show (I release lacewings every spring). You may need to use other methods in combination with your predators. If using pesticides, try to give your plants at least 2 weeks between your last pesticide application and when you release the predators, as pesticides will kill the good guys too!
Pesticides
There’s two main ways that pesticides can work: systemic (absorbed by the plant with the intention that the pest eats the poison), or topical/spray (intended to kill the pest that touches it).
Make sure when using spray pesticides that you are not spraying blooms, or that blooms are not expected for the two weeks that a systemtic pesticide is usually effective. These chemical sprays will poison butterflise and bees just as much as they’ll kill mealies, and can even have negative impacts on your local hummingbirds.
Many of the Bonide brand slow-release systemic granules can be effective, and for plants with powdery farina you want to preserve or a dense fluffy crown, this may be your best bet for eradicating an infestation. For my Coryphantha above, I had to mix granules into the soil in combination with a spray I used on the exposed flesh with no fuzz.
I alternate my pesticides when using sprays to cover as wide a range of potential pests as possible, and to ensure they don’t become resistant. I prefer to use a perimeter spray after the last expected rain of spring, usually around May or June, and create a barrier around my plants to try and prevent ants from moving in (can you tell I didn’t do that this year?).
When bringing home new plants or if I see an active infestation with ants in the soil, I’ll use the typical Bioadvanced 3-in-1 insect, disease, and mite control. The active ingredients are Imidacloprid, Tau-fluvalinate, and Tebuconazole. This is also a systemtic pesticide, so even with rain, it’ll keep working.
For broader applications and in-ground plants, I use the Complete Insect Killer to help with grubs, fleas, and mosquitoes, which also has Imidacloprid but is paired with Beta-cyfluthrin.
I use the “big guns” for the greenhouse and indoors – TalStar is a long lasting residual pesticide that targets insect nervous systems, causing them to weaken and eventually die. It is not immediately effective, and relies on the bugs walking on or through it, so its not great if you’re looking to immediately knock out an infestation. It works best as a barrier, and before we got chickens, I would spray around the base of my potted plants each year. It is toxic to birds and reptiles, however, so I no longer use it where wildlife or our pet creatures can get near it.
In my greenhouse, it’s been fantastic as a method for keeping ants out, which have been the biggest issue with my efforts to eliminate mealybugs. It lasts up to 3 months, so I expect to just have to reapply every season since the interior of the greenhouse is sheltered.
Things That Are Not Mealy Bugs
The tell-tale fuzz that comes from mealies can be hard to tell apart from things that are totally natural and just the way the plants grow. Below are plants from my collection that distinctly do not have mealy bugs, but might fool a new grower.
This notocactus is definitely a prime target for mealies, as they love the fuzz, the crestign, and that there’s lots of dense little nooks and crannies to hide in.
There are no mealies or signs of mealies anywhere on this cactus, though.
This is another cactus that can be a target for mealy bugs. The deep grooves and cresting of the body are super tasty to mealy bugs for whatever reason.
The small white fuzz at top, though, isn’t from mealy bugs – it’s where some spent blooms were attached. There’s no black mold, no stringy fuzz, and no signs of mealy poop.
The shape of the spine areoles, particularly near the top of this echinocereus, can strongly resemble little mealy bug bodies with fuzz.
There’s no mealies on these cacti, though! When I have seen mealies on similarly spined cacti, the first sign is usually egg sacs at the ends of spines. The mealies themselves will hide in the apical growth point of the cactus, where the new spines and fuzz will hide them.
Gymnocalycium pflanzii with some leftover seeds and fruit, as well as slightly fuzzy areoles.
This is a cactus that is a candidate for occasional brushing with a paintbrush to check for mealy fuzz.
As with the echinocereus left, the first sign on a larger spined cactus like this is often the egg sacs at the end of the spines.
