Scale are sap sucking pests that attach themselves to the twigs, branches, leaves and fruit of host plants. Common on backyard trees, ornamental shrubs, greenhouse plants and house plants. There are over 1,000 species of scale insects that exist in North America.
They’re oddly shaped and immobile pests that often resemble shell-like bumps rather than insects. In most cases, heavy infestations build up unnoticed before plants begin to show damage. Large populations may result in poor growth, reduced vigor and yellow leaves. If left unchecked, an infested host may become so weak that it dies.
Scale insects can be divided into 2 groups:
Armored (Hard): They secrete hard protective covering about 1/8” long over themselves, which is not attached to the body. The hard scale lives and feeds under this spherical armor and doesn’t move about the plant. They also do not secrete honeydew.
Soft: They do secrete a waxy film up to ½” long that is part of the body. In most cases, they’re able to move short distances (but rarely do) and produce copious amounts of honeydew. Soft scale varies in shape from flat to almost spherical.
Adult females lay eggs underneath their protective covering and move about the plant until a suitable feeding site is found. Young nymphs insert their piercing mouth parts into the plant and begin to feed, gradually developing their own armor as they transform into immobile adults. They don’t populate and may have several overlapping generations per year, especially in greenhouses.
Males of many species develop wings as adults and appear as tiny gnat-like insects. They’re rarely seen and don’t feed on plants. The females do feed on the plants, and are capable of reproducing without mating.
To gain control of a scale infestation its best to consult a professional, but if you want to try a home remedy you can try the following:
- Prune and dispose of infested branches, twigs and leaves.
- When in low numbers they can be picked off by hand.
- If the infestation is light dab the pests with an alcohol-soaked cotton swab.
- Using lady bugs as a natural predator.
- Using an insecticide soap can be used to kill the larvae. Because of its little persistence to the environment, several applications during the egg hatching will be required for effective control.
- Azamax can be sprayed to make the pests resistance impossible to develop.
- Using horticultural oils will smother insects and will control all pest stages.