All about mealybugs, cacti and succulents
Mealybugs are small creatures that, just like us, love cacti and succulents. We often get questions about them: how do you actually recognize them? Are they actually mealybugs, or just fluff or a piece of perlite? Because these creatures often occur alongside cacti and succulents, we've written a fun and informative blog post about them. This way, you'll learn exactly how to recognize mealybugs and the best way to treat your plants.
What is a mealybug?
A mealybug is a small insect that feeds on plant sap from your cactus or succulent. They are oval-shaped and whitish-gray in color. Young aphids are 1 mm long, while adult females can grow up to 5 mm and have many woolly threads around them. Males are smaller than females and develop wings. This allows them to fertilize many females. Females change very little throughout the stages. They only grow larger and their mobility changes.
When the eggs hatch, the tiny mealybugs are also called crawlers. This is because they can move quickly across the plant. They look for a good place to hide and eventually nest. They don't suck sap from the plant at this stage.
The next stage is the nymphal stage. The mealybugs have grown larger and begin feeding on plant sap. They still move at this stage, but very slowly. After this, they develop into an adult mealybug. The male has no mouth and cannot feed. For this reason, it searches for females for breeding. The female mealybugs build a woolly nest around themselves. They lay their eggs in it, after which they die. And so the cycle begins again. The eggs hatch after 6-8 days under ideal conditions.
What damage does a mealybug cause to the plant?
Mealybugs suck the nutritious sap from the plant. This stunts growth. You might see oddly shaped leaves, yellowing of the leaf or the cactus's top. In addition, photosynthesis in the plant decreases. This makes your plant weaker and more susceptible to the next point.
Plant sap contains a lot of sugar and very little protein. Mealybugs need a lot of protein, so they absorb a lot of plant sap. They excrete the excess sugar as honeydew. This creates a fertile breeding ground for fungi (both beneficial and harmful). Because the plant has weaker immune systems, this can cause damage.
How do you get mealybugs?
This can have many different causes. Sometimes you suddenly see them on plants you've had for years, but they can just as easily appear on plants you've only had for a few months. Below, we've listed the most common causes for you.
- The mealybugs can get onto your plants via air currents from outside through the house.
- They can hitchhike with you on clothing if you have come into contact with them through another plant they are sitting on.
- The male mealybug can fly. It can simply fly in through an open window or door and land on your plant.
- They arrive on new plants, after which they can spread to other plants.
The causes mentioned above are the most common causes of mealybugs. There are certainly others that occur sporadically. Do you have many plants together, for example, in a greenhouse or on your windowsill? And do you see a lot of ants crawling around the pots? Then you might also want to check for mealybugs. Ants love the sweet substance that mealybugs secrete. They protect the mealybugs from predators. They often do this by grouping them together for easier access. This is also how the mealybugs move from one plant to another.
Should I inspect my plants every day and how do I recognize them?
Because of the above, it might seem impossible to keep mealybugs out. In practice, it's often quite manageable. I certainly wouldn't start frantically inspecting your plant every day. You can do this every few weeks. It's more important to know where to look and what they look like. Mealybugs are small, oval-shaped creatures, measuring 1-5 mm in size. Young mealybugs don't have wool yet, but older adult females do, and the wool is white. Mealybugs like to settle in places you can't immediately see. They're almost always found in the same places on your cactus or succulent. We've listed them below:
- In succulent plants with leaves, they are usually found on the underside of the leaf or in the leaf axil (this is the part where the leaf attaches to the plant).
- In cacti, they are found between the spines at the top of the plant or often between the ribs. This is where young mealybugs, in particular, can hide.
- Always check 1-2 cm from the area where your cactus or succulent will be planted. They can hide here easily, and this is a part of the plant where they can easily extract sap.
- Spent cactus flowers. For some reason, they have a preference for these, especially the larger flowers. Once these have finished blooming, they can remain on the plant for a while. Once they're dry, you can often remove them. If you want seeds and are waiting until the seed pod has ripened sufficiently, you can check this carefully.
- Some species, such as Aeonium and carrion flowers like Huernia and Orbea, are particularly susceptible to mealybugs. Given a choice, they'll always choose these plants. Therefore, check these species more often.
- Some cactus and succulent species have external characteristics that closely resemble mealybugs in shape and color. Think of the spots on an Astrophytum, or the white areoles of various Mammilaria or Opuntia species. Also, the scale-like leaves of an Avonia. These plants are not more susceptible to mealybugs, but you should monitor them closely because they can easily hide there.
- Pay extra attention to plants with low resistance. Plants that aren't doing well are more susceptible to mealybug infestation.
The above points are especially helpful in detecting an incipient mealybug outbreak. This makes it quick and easy to treat. As the outbreak grows, you'll naturally see them in various locations across the plant. But initially, when there are just one or a few of them, they almost always choose to nest in one of the locations mentioned above.
What can I do about mealybugs?
Fortunately, there are many things you can do to combat mealybugs. Have you found a plant with mealybugs? We recommend isolating it from the rest of your plants for a while. This will prevent further spread. Control methods depend on the severity of the infestation. Below, we describe a few home remedies, including natural predators and a biological pesticide we've personally used. We won't discuss chemical pesticides, as they are often harmful to the environment and to many other living organisms besides mealybugs. The decision to use these products remains yours; we don't advocate for them.
If you find one or more mealybugs on your plant, you can dab them with a brush or cotton swab dipped in alcohol. Mealybugs can't tolerate this.
If there are several, or you're unsure whether you've missed any, you can also spray the plant with a mixture of water, liquid green soap, and methylated spirits. The ratio: 500ml water, 10ml green soap, and 10ml methylated spirits. Especially with waxy succulents, test on a single leaf first to ensure it doesn't cause discoloration, which could damage the protective wax layer.
These home and kitchen treatments work well. Monitor the plants for two weeks for new mealybugs hatching from the eggs, and re-treat if necessary. Under ideal conditions, mealybugs hatch after 6-8 days. In colder weather, this can take a little longer. For this reason, we recommend a 14-day period. This ensures you've also caught the later hatched aphids.
An organic product we've had good experiences with and still use is Organifer's Leaf Insects. We started using it because we wanted to get rid of chemical pesticides. A major advantage of this product is that it can be used both preventatively, against mealybugs found, and as a systematic treatment. A significant drawback is that it smells quite strongly of garlic, so we recommend not using it indoors but taking the plants outside and treating them there.
Organifer's Leaf Insect product penetrates the plant and gives the sap a foul taste. If you use it preventatively, new mealybugs will be less likely to settle on your plants. If you use it curatively, the mealybugs already on the plant will starve. You can apply this product to the plants by spraying it on with a plant sprayer. We recommend spraying the plant thoroughly so that it covers all of your cactus or succulent. You can do this once a week for 2-3 weeks. You will see the mealybugs decrease during this time. Sometimes they remain on the plant but are already dead and fall off easily when touched. If you spray the product on, we recommend not misting or spraying the plants with water during this period. This dilutes the product and makes it less effective.
You can also apply the product while watering. This way, it works systematically and reaches the pests at the roots. If you do this, we recommend maintaining the same watering frequency as usual. Watering more often increases the risk of rot. We recommend watering from above only if your pot is sealed. Otherwise, all the water will run off and the product will be less effective. If you don't have a sealed pot, you can place it in a saucer.
Interested in Organifer Leaf Insects? Links to the product can be found here and at the bottom of this blog post. Mixing ratios can be found with the product information.
A third and effective method of control is the use of natural enemies. This has the advantage of being biological and certainly effective, because the natural enemies know where to look and thus find the well-hidden mealybugs. It also has disadvantages, however: you have to be aware of suddenly having a whole new group of creatures in your home. Natural mealybugs also eat a lot, so if you have a few aphids, the natural mealybugs will quickly starve to death, often before any new eggs have hatched.
There are also minimum and maximum temperatures. While mealybugs aren't particularly affected by these, their various natural enemies are. This usually isn't a problem indoors, but if your plants are in a greenhouse, it's something you need to keep in mind during cold or warm spells in winter and summer. It's best to check the temperatures at which each species is active.
These days, you can easily order natural enemies of mealybugs online, and they'll be delivered to your door. Two examples you can use for this are listed below.
- The green lacewing, Chrysoperla carnea
- Crypto larva, Cryptolaemus montrouzieri predatory beetles
- What else can I do preventatively?
Besides monitoring, you can also help strengthen your plant's resistance. Mealybugs often choose plants with poor resistance. This doesn't guarantee they'll avoid healthy plants, but it can make your plants more resilient. Good resistance often goes hand in hand with the right location for sunlight and warmth. You can feed once a month during the growing season, and if your plant has been in the same soil for many years, you can repot it and add new soil. Both help boost your plant's resistance.
Another thing to watch out for is drafts. Is your plant in a draft in your home? Then there's a greater chance that mealybugs will end up on your plants in this airflow.
We hope you can get started protecting your plants against mealybugs. Did you enjoy reading the blog? Or is there any information you need? Let us know!
