While those unfamiliar with their tyrannical reign may just see small bumps on the trunk of a shrub or tree, gardeners see the life-sucking insects infesting their poor plants. Scales are tiny insects with shells that attach to a host plant, like parasites. Left unattended, these armored nightmares can cause serious damage to a plant.
What Are Scale Insects?
Scales are tiny, armored pests that can be easily overlooked. While the various species differ in appearance, the majority of scales are oval or circular, wingless, and lack any distinct body parts, such as a head or legs. Ranging in size from less than 1/8 of an inch to ½ an inch, they come in a variety of colors, including black, brown, grey, and green.
The main victims of scales are trees and shrubs, but these pests will sink their mouth parts into most perennials. They feed off the sap of branches, attaching to fruits and leaves as well. Where there is one, there are generally many, many more covering an area. When feeding, the pests can cause major damage, up to branch dieback and eventual death of the plant.
It is important when treating for scales to identify the type that is attacking your plants, especially since there are scale look-alikes. Take a picture and search online for a matching description to know which species is the culprit.
How to identify Scale Insects
Finding the exact type of scale can be hard with over 7,000 species of scale. Different scales will feed on different plants, so include the plant when trying to identify the scale. The best ways to search for them is based on an outward description, which can be divided into two types:
Armored scales have flat, plate-like covers over their bodies and reach 1/8 inch in diameter. Removing their covering will not remove the insect itself, but rather just exposes the parasite’s body to the environment. Most armored scales lack appendages and once settled on a plant will remain there feeding for the rest of their life.
Soft scales, on the other hand, can group up to ½ inch long and have a smooth, waxy surface covering. Unlike armored scales, their coverings are attached to their actual body, meaning that removal of the surface removes the pest as well. After settling, they are able to move slowly to new areas.
Some scales will secrete honeydew, a sticky fluid that other bugs will feed off of, especially ants. Another sign of scale infestation is the appearance of sooty black mold on leaves, a direct effect of honeydew drippings.
Scales hatch from eggs over 1-3 weeks and experience two growth stages before reaching maturity. The larvae, called nymphs, will insert their mouthparts into the plant and feed throughout the rest of youth and adulthood. They usually overwinter as eggs and produce several generations in a year. When it comes to prevention, the best time to control populations and damage is early spring.
How to Get Rid of Scale Insects – Control Methods for Scale
If scales haven’t completely overtaken a garden or plant, it is possible to hand pick the pests off. Try rubbing the insects off with a scrub brush or similarly rough surface that won’t hurt the plant to remove them.
One of the few nice things about scales is that they make excellent fodder for other bugs. Introduce lacewings, lady beetles and other predatory insects to your garden to help control populations. Parasitic wasps can kill off adult scales by laying eggs in or on the pests, causing the shells to become puffy or dark.
Pruning back the infested areas of a plant is an excellent way to remove the scales without chemicals or spending hours picking at tiny shells. Cutting back to open up canopies in the summer can also reduce some scale populations due to the heat exposure. Remember to use proper pruning techniques to avoid permanent damage.
Use neem oil on light infestations to reduce feeding and repel new scales. Neem oil is found in seeds of the neem tree, is non-toxic, and can help control scales by dabbing with a cotton swab. It can also affect the scale’s hormones, making it harder to lay eggs or for nymphs to mature.
Horticultural oils can be used if the infestation becomes uncontrollable. These work by covering the area and suffocating the pests caught in the spray. These don’t harm mammals but will kill any beneficial bugs caught in the crossfire. While they do not cause harm to the host plant, it is always important to double-check the labels for the most environmentally friendly ones.
How to Prevent Scale Insects
In early spring, wrap double-sided tape around the branches and twigs of high-scale areas. The nymphs will crawl across the tape and get stuck, unable to move or latch onto the tree. Change out the tape wrappings throughout the spring, noting the number of little orange/ yellow specks (the nymphs). When the specks drop in number, you can remove all tape traps as the majority of scales have settled or been caught.
Use water-sensitive paper to determine the presence of honeydew droppings from scales. Regularly check the papers set up beneath the plants to determine how detrimental the infestation is and what the best treatment will be going forward.
If you have ants around the scale-affected area, treat them too. Ants are drawn to honeydew and will attack beneficial insects that prey on scales. Treat the ants and/or deny them access to the plant using sticky traps around the bases.
If you find yourself with a scale infestation, take action as soon as possible and follow up with preventative measures in the future. While they may appear to be innocent little bumps, scale infestation can cause real problems and nightmares for a gardener. With proper identification, prevention and control, you can keep your plants scale-free and healthy all year long.
Learn More about Scale Insects in the Garden
My hibiscus plants have been being attacked by I believe spider mites and aphids. I’ve treated them with both neem and horticultural spray however the infestation remains. I kept them in my basement over winter and found the bugs once again attacking new leaf growth and the top branches. Now the plants are outside however look like they have gone dormant or are dying. I cut the branches back that were dead and noticed the bark slid off the branch thats still alive showing sticky black stuff underneath. Now even the base of the plants bark is beginning to show wrinkles on the bark. Is it too late to save them? Now to top it all off my seedlings in my basement are also being attacked, even though it was almost 3 wks later after the hibiscus was brought outside before I sowed them and put them downstairs. What pest can last with no host in a warm dry atmosphere with no food? Any help is greatly appreciated.