Plant problems: Mealybugs

The unmistakable mealybug.  

The unmistakable mealybug.  

Mealybugs are little pests that are so good at hiding in the nooks and crannies of plants that you might not even realize you have an infestation before it's too late. They will slowly suck the life out of your plants, and can be a pain to fully get rid of depending on the severity of their infestation.

First off, let's identify what a mealybug looks like. If you notice tiny, white cotton-like masses on center leaf veins, under the leaves, or at the joints where a leaf meets the petiole, you've got mealybugs, or mealies for short. Mealies are a type of scale insect found all over the world in moist, warm climates, and there are over 200 species in the US alone! Since they're native to more tropical climates, it stands to reason that mealies are often found on our tropical houseplants. I've had a few mealy infestations and they usually hitchhike in on plants that have been raised in greenhouses (i.e. warm, humid surroundings). I've also had mealy infestations arise from potting soil that was ridden with eggs. Yikes! 

Mealies feed on the the juices of a plant and in bad cases, they will cause leaves to yellow, curl, and drop. As mealies feed, they secrete a clear, sticky substance called "honeydew," which is made up of sugar and other compounds. The honeydew alone doesn't harm the plant, but it does tend to attract other pests! It's like a little alarm for bugs saying "hey, here is a plant that you can eat just in case you missed it!" Sometimes you'll see the honeydew before the actual mealybugs, which is your first warning to get the pests under control before it's too late. This is also why it's a good idea to check up on your plants weekly, even the low maintenance ones like a ZZ plant or snake plant... you never know what might be hiding. 

So, what do you do if your plants have mealybugs? As soon as you notice them - or any pest for that matter - isolate the effected plant and immediately check surrounding plants to make sure the little beasts haven't spread. I advise starting with the least invasive pest control methods first before you reach for intense chemical insecticides. There's certainly a time and a place for chemical insecticides, but a small infestation doesn't need the big guns just yet!  

How to get rid of mealys:

  • Pruning: use clean, sharp shears to snip off any parts of the plant that are clearly suffering from mealybug damage.
  • Rubbing alcohol: rubbing alcohol is a tried-and-true method that works well on smaller mealy infestations. Dip a cotton swab in rubbing alcohol and gently wipe the mealies off the leaves and stems, making sure to check joints where mealies like the hide. The rubbing alcohol dissolves the waxy white coating that protects the mealybug, but doesn't harm the plant. Check back every 3-4 days to make sure that no more mealies pop up. Rarely will you only do one application of any pest control method - it usually takes a couple tries to fully eradicate them. 
  • Neem oil: Neem oil is a natural pesticide that usually comes in a concentrated form that you mix with water. Spraying it on the plant not only helps kill pests, it helps prevent them as well. It also acts as a natural leaf shiner! I will warn you that neem oil has a very strong, distinct odor reminiscent of citronella, so spray the oil outside so it doesn't stink up your house! 
  • Changing the soil: sometimes eggs are hiding out in the soil and only treating the leaves and stems doesn't take care of mealies for good. There are even some species of mealies that feed on roots! In these cases, you will need to completely change the soil. Let the soil dry a bit, remove the plant from its container, then shake the soil off of the roots (preferably in an area where there aren't other plants). Wash the roots clean, let them air dry, and then repot into fresh soil. Some people bake their soil in the oven to kill any potential pests; this isn't something I've ever done, but I've read plenty of explanations on houseplant forums if you're interested in learning more about it. 

What if you've tried all of these methods and the mealybugs keep coming back? You definitely have options, so don't give up just yet! 

  • Lacewings, ladybugs, and mealybug destroyers: if you have a very bad, widespread infestation on many plants, look into purchasing these natural enemies of the mealybugs! They won't harm your plants and will fly away after they've eaten the mealies. There are plenty of reputable websites that sell these live insects. Homestead Brooklyn on YouTube has a great video about these pest destroyers in her series "Plant One on Me." 
  •  Insecticidal soap: if the neem oil or rubbing alocohol isn't working, sometimes spraying down your plant with insecticidal soap can often do the trick. Make sure your plant tolerates the insecticidal soap by checking the label! Some species of mealies are also more tolerant to chemical insecticides than others, so this method can be hit-or-miss depending on the type of mealies you're dealing with. 
  • Systemic insecticide: systemic insecticide can be very toxic, which is why I recommend using it as a last resort if nothing else works. I had to use systemics this summer on a few plants and it was a miracle worker, but I could tell it took a toll on the plants. I let them rest in cool shade for a few days after appication, and treated them all to tepid showers after the mealybugs but the dust once and for all. What exactly is a systemic? It's a pesticide that's placed in the soil and taken up by the plant in it's roots, stems, and leaves. Mealies and other pests that suck on plants are poisoned because the pesticide is in the entire plant's system. The mealies will be sucking up the pesticide along with the plant's juices. Pretty gnarly, huh? For this reason, you DO NOT use systemics on edible plants! Always apply systemics outside away from animals and children, wear gloves, and make sure to thoroughly read the instructions before use! I personally use the Bonide brand systemics for houseplants, which can be found on Amazon