What scale insects attack orchids?
Whatever species they are, mealybugs are biting-sucking insects that attach themselves to the tender parts of a plant, such as leaves, young stems, etc. to feed on it. To do this, they prick the area where they are installed to extract the sap and cells, which causes damage to the plant.
Orchids can be attacked by three different species scale insects which differ in their physical characteristics and their method of laying eggs, but have the same way of life and the means of combating them are identical.
Mealybug
This is the most widespread species of cochineal. It is easily recognizable and visible due to the presence of a white waxy layer that covers the body of female mealybugs, giving it a cottony appearance, hence its name mealybug. As adults, female scale insects do not have wings and do not move although they have tiny legs. Unlike females, males have wings and move to fertilize females.
They resemble, neither more nor less, like midges. Finally, the larvae resulting from eggs laid in ovisacs are brown, then beige and mobile, which means that they can leave the plant where they were born to settle on another nearby. This explains why, if one of your orchids is contaminated, others may be too. As they evolve, they will darken and move less and less.
The shelled cochineal
Less widespread, the shelled cochineal takes its name from gray or brown shell which covers it and which gives the impression of small dark bumps on the plant. If you scratch these little bumps with your fingernail, they will come off. The eggs of this species of mealybug are laid under the shell.
The boisduval cochineal
Known under the scientific name Diaspis boisduvalii, this mealybug appeared a few years ago and is now becoming a real pest in greenhouses. It is comparable to the shelled cochineal, but this shell is white and translucent.
The development stages of mealybugs
Having a brief overview of how mealybugs develop will help you understand why it is important to act quickly. You should first know that mealybugs develop in warm and humid environments, which explains why they often settle on greenhouse or veranda plants, but also on indoor plants, such as orchids between many others.
Where the problem lies is that when climatic conditions are favorable, they reproduce and lay a multitude of eggs and the following cycle will take place over a few weeks:
- After laying, the female dies, but the hatching of the eggs gives birth to as many yellow-brown nymphs, which as we have seen, are very mobile and move from one plant to another.
- In the second larval stage, the female larvae take on a darker color and will settle permanently on a leaf and secrete wax. For their part, the male larvae will then metamorphose and the wings will emerge. The lifespan of males is only a few days, because they do not have a mandible for feeding. They then look for a female to fertilize.
- In the third stage, the scale insects will molt until complete metamorphosis and wait to be fertilized.
This larval development only lasts 1 to 2 months, which means that without human intervention, there can be several generations of mealybugs over a year.
Damage caused by mealybugs
The damage caused by mealybugs, whatever they may be, is multiple:
- Mealybugs feed by biting the leaves, stems and aerial roots of your orchid to suck out the sap, they will weaken it.
- In addition, mealybugs secrete a sticky substance called “honeydew” which the presence favors the development of black microfungi, such as sooty mold, which block photosynthesis. This reduction in photosynthesis harms the health of the plant and its aesthetics.
Identify the presence of mealybugs on your orchid
Only careful observation of your orchid can allow you to quickly spot the presence of mealybugs. Here are some of the signs that should alert you:
- If you notice white clumps on a stem, leaf or aerial root, you can be sure that your plant is infested with mealybugs. Likewise, if you spot some kind of small yellow-orange or brown bumps that you can peel off with a fingernail, this is a sign that shelled or boisduval scale insects have taken up residence on your plant.
- If you notice that leaves are turning yellow and then falling, or a deformation of your plant, you are faced with other signs indicating the probable presence of mealybugs.
- The presence of a sticky substance on your orchid also requires special attention. It could be honeydew.
- Finally, if you notice a kind of black powder on the leavesit may be sooty mold.
Prevent the appearance of mealybugs
Mealybugs grow quickly and, once present, are difficult to dislodge. This is why it is recommended to adopt some preventive actions:
- Before buying an orchid, inspect it from every angle to ensure that you are not going to bring mealybugs into your home. If the orchid was a gift to you, it is a good idea to keep it away from your other plants for a few days. This will avoid cross-contamination.
- Get into the habit to regularly examine take a close look at each of your plants to spot the first signs of the presence of mealybugs.
- When you use tools, whether to water or maintain your orchid or change its pot, it is necessary to disinfect everything well to avoid any cross contamination.
- Ventilate the room regularly where your orchid(s) are located and control watering.
- Also make sure that your plants are not not too stuck together to allow each plant to benefit from better ventilation.
Fight against mealybugs
As soon as you notice the presence of mealybugs, it is important to treat the plant quickly until these pests have completely disappeared. To do this :
- Using your shower head, wash your plant under a powerful jet. Be sure to get under the leaves and pseudobulbs. This will allow you to remove a good number of mealybugs, eggs and larvae, about 80%, from where they are hiding. Don’t hesitate to use a toothbrush to get into the nooks and crannies.
- In a sprayer, prepare a mixture of water, black soap and olive oil. You can also add a few drops of lemongrass essential oil, for example. Once all the ingredients are well mixed, spray the entire plant, making sure to get it on the underside of the leaves, the stems and aerial roots, as well as on the surface of the substrate. Repeat the operation as many times as necessary.
- If your plant is covered in honeydew or sooty mold, it is recommended to clean the leaves with a cloth soaked in this mixture.
- If you are faced with shelled caterpillars or boisduval caterpillars, It is recommended to use alcohol at 70°C to remove them.
- If any parts are too damaged, cut them off.
- If there are a lot of mealybugs on your orchid, change its substrate.