Houseplant pests series part 3: Mealybugs

My last two posts about houseplant pests featured soil gnats and spider mites. The featured pest this time is the dreaded mealybug. I use the word dreaded because mealybugs are one of the most difficult houseplant pests to get rid of, although they are not as common as other houseplant pests. Once you have a plant that has mealybugs, eliminating the pests is extremely difficult, control is a more realistic goal.

So what are mealybugs anyway? Mealybugs are scale insects that suck the sap out of the leaves and stems of plants, resulting in stunted or deformed leaf growth, yellowing of the leaves, and leaf drop. The damage caused by mealybugs is not as quick to occur or as devastating as it is with spider mites. If a mealybug infestation goes left untreated, the plant will eventually die; although it will usually take a long time for mealybugs to kill a plant.

Young mealybugs walking on plant leaf

Mealybugs can be found anywhere on a plant but are most commonly found on new growth, along the veins of leaves, and at the leaf joints. 

They are white and most commonly look like cotton around the base of the leaves or stems of the plant. 

They can also appear brown or cream colored and waxy in immature stages.

Mealybugs look like mildew or cotton on stem

It takes a week or two for mealybug eggs to hatch. Most of the time mealybugs don’t appear to move, but in their early stages, mealy bugs can crawl around on the plant and move to other plants around the original host plant. 

They are commonly mistaken for disease or mildew rather than bugs. 

The worse part is that mealybugs will leave the plant to hide and can live for a long time in spaces and crevices without having a host plant. 

So just when you think you have conquered the beast, they will come out of hiding and re-infest your plant when you’re not looking. Gross!

As with any houseplant pest, when you first spot a mealybug problem begin treatment immediately. In my experience, the best way to control mealybug infestations is to hand treat the plant with rubbing alcohol. In order for rubbing alcohol to be effective, it must come in direct contact with the mealybug. Touching the bug with a cotton swab soaked in rubbing alcohol, or spraying them with a rubbing alcohol/water mixture (50/50) from a spray bottle will kill them. 

Sever mealybug infestation

I don’t use insecticides because they are resistant to most insecticides. They also have the ability to develop resistance to insecticides they are exposed to on a regular basis. As you are treating the plant, make sure to inspect underneath all leaves, around the leave joints, in folds and at the base of the plant for mealybugs. They like to hide so make sure to check the plant from several angles and under each leaf. Also brush away a little dirt and check the base of the stem at the point where it sticks out of the dirt, you may find some hiding there.

Here are some other tips to help in your fight against the mealybug:

• You have to be vigilant and check the plant at least once a week for new adults. When you no longer see signs of the mealybugs, you can go down to inspecting the plant every couple of weeks or every time you water.
• For heavy infestations, spray the entire plant with a rubbing alcohol/water mixture (50/50). You may want to test this spray on one leaf first to make sure this mixture won’t harm the plant.
• Mealybugs can live in the soil of the plant, so if a plant is plagued by recurring infestations, you may want to try repotting it in a clean, sterile pot with fresh potting soil.
• Remove the plant from the area and clean the area around the infested plant in any crevices, around the outside lip and inside edges of the pot and tray and other small space where mealybugs may hide.
• Remember, mealybugs can travel so it is important to monitor other plants around the plant for signs on mealybugs.
• If you have ants, they may be causing the problem! Ants will bring mealybugs to a plant so that they can feed off of the honeydew which is produced when a mealybug feeds on the plant. I know this sounds crazy, but it’s a fact. So make sure that you watch out for ants.
• If you don’t want to spend the time it takes to control/conquer a mealybug infestation, it may be best to discard the infested plant before the problem can spread.
• For other tips on general indoor plant pest control, see my Pesty Pests blog post.

It's hard to get rid of all of the mealybugs the first few times you try. Even if you are able to kill all of the adults, the eggs and babies are tiny and easily overlooked. They don’t affect most of the common houseplants. It can be frustrating, but for me, it is worth the work to control these pests. I hate throwing away plants so I continue to fight the good fight!


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