This in my opinion is one of the worst bugs in Bonsai. It can be hard to find, hard to kill and usually only attacks trees that are already sick or stressed in some way. Mealy bugs tend to hide in the leaf axils, roots or any cool dark place where they can suck the life juices from your prize trees undisturbed. If you move aside dense foliage or twigs on a plant that is showing a lack of vigor you can usually find them. They can be identified by their white waxy meal that gives them their name.
Mealy bug in nest notice sooty mould around the infected area
They can be identified by their white waxy meal that gives them their name. They are mobile oval shaped bugs about the size of the top of a click in button on a bic pen (about 1mm in diameter). You may have to poke around in the waxy substance and the associated sooty mould to find a live one. If you have an infestation on the foliage of your tree and you are using manual methods to remove them it may also pay to check the roots they are also quite at home in the soil.
Mealy bugs on roots
Notice how this plant is quite root bound this will be contributing to the plants stress and making it the ideal cantidade for infestation
Mealy bugs are most abundant in the warmer periods especially late summer and autumn. Some of the species practice parthenogenesis, which is the worrying technique of having babies without the input of the male. Eggs or sometimes live nymphs are deposited in nests of the waxy material some times several generations in one season.
The problem with Mealy Bugs is they have developed a great protection from spray by coating themselves with a water proof wax. This means that contact sprays will have little to no effect on the bug population, the only way to get them is using systemic sprays such as Orthene or Confidor. These sprays are taken up by the plant so you are in effect poisoning their food supply. It is also advisable to add a little organic spraying oil to the mix, this helps break down the waxy substance. Always check that your plant can handle this type of cocktail before spraying your prize tree. A lot of plants do not like oil and some plants don’t like systemic sprays (Chinese Elm for one). If you want to go organic on it the best idea would be the oil on its own, again check your plant can handle it before you spray. You will have to repeat any sprays several times especially if you are using just oil. If you would like to be even more hands on and hunt these little tree suckers down, you can dip a small brush in mentholated spirits and dab it on each bug. This causes them sever harm. The young bugs are however very small and difficult to see, if you only have a small tree and are prepared to keep at it this method can be successful.
The Ladybird just love Mealy Bugs
There are a few bugs that will help you in your quest to destroy mealy one of them is the ladybird. The steal blue coloured bug will hunt down and eat both scale and mealy bugs. The orange with black spots ladybird is a real mealy killer. It lives solely on mealy bugs. The larvae of this bug will hunt the mealy and even go so far as to covering themselves with the waxy secretions as camouflage so the can sneak up behind their pray and jump them. There is also a little parasitic wasp that feeds on mealy. These natural control agents may be enough to reduce numbers sufficiently on a garden plant but any mealy on a bonsai is too many so you may have to step in and help. Once you have them under control check you plants physical condition, you will usually find it is under some sort of stress. It may need a repot, different soil condition more or less watering etc. Mealy are also quite common on plants that have been kept indoors for too long. The elements, wind, rain and sun also help to keep populations down.