Mealybugs are every succulent grower’s nemesis and are pretty much inevitable when you grow succulents as mealybugs really love feeding on this group of plants. What makes mealies such a monumental pain in the backside is their ability to survive, hide from plain sight until the infestation becomes quite bad and spread quickly. In this article, we will share all we know about mealybugs (as a working nursery we have had our fair share of encounters with the little buggers), their life cycle, how to identify mealybugs, how to prevent & control them, their relationship with ants and which succulents are particularly prone. We will also put some of the control methods to the test. For those of you who do not feel like going through the whole article, I have compiled a quick mealybug FAQ.
No, mealybugs are not dangerous to humans. Squashing one may cause mild skin irritation, though this is unlikely. Mealybugs also carry bacteria, but there is no known crossover to humans.
No, mealybugs are not known to be harmful to dogs, cats or any other pets.
Although the answer is, eventually yes, mealybugs can survive underwater for a long time, and we would not recommend trying to drown them as a means to destroy them. Mealybugs should be killed either by squashing or chemically.
Yes, mealybugs can most certainly infest a house. They can get inside in contaminated potting mix, other plants, fruit, veg or flowers. Young mealies are fast crawlers and can even get in through gaps in the window as they are tiny.
Yes, mealybugs can live in the soil. Ground mealybugs are subterranean and feed on plants roots. They can also hide and lay eggs in bigger chunks of the potting mix (pine bark fines etc.)
No, ants do not eat mealybugs. Ants protect and farm mealybugs for their sweet excrement called honeydew. Ants collect and feed on this honeydew. They will also fend off any mealybug predator and move mealybugs to desirable plants. If there are ants near or on succulents this usually means there are either mealybugs or aphids present.
Although Neem Oil is listed as an effective and green solution to controlling mealybugs and ants, as a working nursery, we did not have much luck with it (although this is only our experience). Neem Oil may help with young mealies, but it will probably not kill them all. We will conduct a video experiment on some infected plants using Neem oil further down. You can comment below the article to share your experience with Neem Oil and mealybugs.
No, mealybugs are crawling insects, though adult male mealybugs can fly. The older mealybugs get, the less mobile they seem to be. A young nymph can crawl fairly fast and travel from one pot to another and can crossover to other parts of the garden.
Ants farm mealybugs for their honeydew sap (similar to humans milking a cow) and will spread and protect these pests from predators. Ants can bite with their mandibles and mouths, and some can also sting. Ants use this to warn off mealybug predators. Research shows that mealybugs would be much more vulnerable to predators if it weren’t for ants.
Mealybugs can crawl from plant to plant, and young nymphs seem to able to travel faster and further than older mealybugs. Ants will also carry mealybugs to new hosts as will (without knowing) humans that may be giving mealybugs a hitch on themselves or on gardening tools. Male mealybugs can fly too.
Mealybugs can start in your garden by crawling from another host nearby, though they can also start by ants, humans, contaminated potting mix, on shovels/ other gardening equipment, by buying a new contaminated plant and even by air currents.
A spray of isopropyl alcohol is usually safe, but it can cause dark burn marks on some sensitive plants, especially on new growth or if there is a wound on the foliage. A 70% solution of isopropyl alcohol (70% alcohol + 30% water) is more gentle than 100% alcohol. To avoid/ minimize the marks only spray on a cool day and in the evening so the plant is not exposed to sun, which can make the marks worse.
Mealybugs leave small clues on plants such as white marks/ streaks on stems and leaves and can often have a white, cotton-like sack protecting them. Curling leaf growth is also a dead giveaway of mealybug presence. They may, however, be very hard to spot on some plants as they can hide deep between the leaves, in dead leaves and also in roots, only becoming visible when there is a serious infestation.
Male mealybug looks like a tiny fly with a long waxy tail. They have wings, and their purpose is to fertilize the female who will then lay eggs. Male mealybugs will feed when still young, but once they mature the wings develop, they find their female and die shortly after.
There are a few mealybug predators out there. Insects such as ladybugs, lacewings, parasitic wasps, spiders and the mealybug destroyer (Cryptolaemus) all eat mealybugs. It is important that ants are not allowed near mealybugs as they will protect them from these predators.
No succulent is safe, and we have found mealybugs on a great range of plants (even the ones mentioned here), though they definitely do have favourites. Some plants very rarely get attacked. They include Ceropegias, Haworthias, some Sedums (Green Mound, Gold Mound, Acre), Echeveria Elegans, Echeveria Violet Queen, Senecio Rowleyanus, Senecio Radicans, Cotyledons, Euphorbias, Kalanchoes.
Mealybugs love succulents that are chunky and have a tight spot for them to hide in, usually where leaves meet the stalk. Their favourites include but are not limited to Graptoverias, Graptopetalums, majority of Echeverias, Graptosedums, Pachyverias, Aeonium, Crassula, Senecio Serpens, Sedeveria, chunky Sedums (Rubrotinctum, Pachyphyllum, Clavatum)
If mealybugs are not caught in time, yes they will spread. Once an egg is laid, the crawlers will look for plants to feed on and will disperse. One female can lay over 200 eggs. That is a lot of potential mealy bugs set loose among your plants.
Mealybugs are soft-bodied, scale insects that live in warm and humid habitats. They are covered in a white waxy substance and have a rubbery coating. The shape can vary from species to species and can be globular, oval or flat. Unlike other scale insects, mealybugs retain their legs and can move in adulthood. Mealybugs usually appear during the warmer months and in greater numbers if it is raining consistently. Mealybugs are considered a pest as they feed on plants juices and are also vectors for plant diseases. In a greenhouse, these pests can live all year round.
A complete lifecycle of a mealybug can range from just over a month to two months. Mealybugs start their life as an egg, although some species can lay live young. A female mealybug can lay over 200 eggs in a white, cottony sack which protects the eggs until they hatch. The female mealybug will die shortly after laying the eggs. Mealybugs emerge after 7-10 days as crawlers and are quite small and much faster than adults. They will usually disperse to find a host plant in which they will hide and feed on. Female mealybugs feed on plants all their lives, but male mealybugs will eventually grow wings and stop feeding in adulthood. They will then spend the rest of their very short life looking for a mate and die soon after they fertilize the female.
In our opinion mealybugs are pretty much inevitable if you grow succulents, even more so if you live in a country with mild winters. You would have to be extremely lucky to never encounter a mealybug on your succulents. To try and prevent mealybugs from spreading is the key to not have much trouble with these little pests.
Any new plants brought home should be inspected for mealybugs. Check between the leaves, on the newest growth and under the rim of the pot. Existing plants should also be checked every other week from spring to autumn.
We would also highly recommend re-potting plants yearly so roots can be looked at for mealies that feed in the soil.
Shrivelled up dry leaves should be cleaned off the plants regularly as this is a favourite spot for females to lay eggs.
Females also lay eggs on surfaces, under the table, under the rim of the pot, at the bottom of the pot, under the water tray or in ornaments close to plants. It is a very good idea to keep areas around plants clean as mealybugs like mess, fallen leaves that provide a great egg-laying place and clutter around pots. We often clean our tables, sweep fallen leaves or spilt dirt and spray alcohol solutions under the table and in trays. Keeping your plant area clean and tidy will minimze the chance of mealybugs laying their eggs in the first place.
If there are lots of ants in the area, make sure that they are not anywhere near succulents. Ants on succulents is never a good sign. Even if you have mealybugs chances are there will be predators in the area looking for their next meal. Ants will, however, make sure mealybugs are safe from these predators so they can keep collecting the honeydew.
If you grow many succulents, it could help to mix them up a bit. Plants that usually do not get attacked can be put between those that are mealybug favourites. This may confuse the mealybugs, and if they do attack, they will stay on the one favourite plant making it easier to kill them, rather than spread all over the place. If you have many of their favourites all together chances are the crawlers will infest each and every one of the plants as they are close.
In the nursery, we also like to put random herbs and smelly plants such marigolds on tables with succulents in hope their scent may confuse mealybugs. Although there is no scientific evidence out there proving this works, there are other benefits. When herbs are allowed to go to flower mealybug predators are likely to move in as they like herb blooms. There is also some limited evidence suggesting ants do not like mint, so we have large pots of mint around too.
Mealybugs are notoriously hard to control especially once there is a serious infestation with a side of a healthy army of ants acting as mealybug bodyguards.
The first thing to do to control mealybugs on your plants is to isolate any plant with mealybugs on them. It needs to go as far from other plants as possible. You just never know how many mealybugs there are and if any crawlers are present. Crawlers are hard to spot when freshly hatched because they are tiny.
Second is to kill any visible mealies with a toothpick or just squash between fingers. Killing them manually like this will ensure that they are well and truly exterminated. If there are too many of them and in tight spots a spray with 70% isopropyl alcohol should kill a few. We have a video coming soon of an experiment with alcohol, neem and a homemade solution. Neem Oil, Insecticidal Soaps and some home remedies may help a little with a mealybug infestation, though it is unlikely all mealies will be killed. In our experience harsh insecticides do not work very well either as the waxy coating repels anything that comes into contact with mealybugs. Isopropyl alcohol seems to have some effect in getting through the wax, but we have noticed that not all mealybugs are always killed after application. Harsh insecticides are also extremely bad news for beneficial insects as they usually kill them and so we do not recommend using insecticides at all.
The third thing to do when mealybugs are found is to prevent ants from accessing plants. Without ants present, natural predators should take care of many mealies.
Four, clean the area, check the pots and any crevices that may provide a safe egg-laying or hiding spot.
If you have a greenhouse or grow many plants, it may be worthwhile to purchase the mealybug destroyer (Cryptolaemus Montrouzieri). These mealybug eating insects can be purchased and released in your garden/ greenhouse, though do make sure ants can’t attack them.
Continually check other plants for signs of mealybugs and kill any as soon as they are spotted.
Do not feed your plants nitrogen-rich fertilizers during an infestation as this will cause tender new growth which mealies love to feed on.
If you have a favourite mealybug fighting technique, you can share with us in the comments below.