Different in appearance from other damaging insects, scale have no apparent head or segmented body parts. Heavy infestations are sometimes present before symptoms of damage appear. Scale usually looks like a bump or blob on limbs, stems and leaves and sucks the juices from the plant to which it is attached. Shell-like lumps about 1/8 to 1/4 inch in diameter are most likely scale.

Different Types of Scale

Brown scale

Brown scale insect protected by scale

Black scales

Adult and Nymph Black Scales

There are soft scales and armored scales, both secrete a substance that covers the body and protects them. Most are circular to oval. Some change shapes as they grow. Some scales have both male and female, others have no males and females reproduce without mating. Armored scales, oak pit scales, and sycamore scales do not secrete the honeydew substance, but some soft scales do and as a result ants appear to feed and protect the insect.

Armored scales include cycad scale, euonymus scale, oystershell scale, and San Jose scale, according to CA Davis IPM. Soft scale varieities are black scale, brown soft scale, Kuno scale, lecanium scales, and tuliptree scale.

Scale Look-Alikes

And there are scale look-alikes. “Various other organisms resemble scales but have different biology and management. These include California laurel aphid (Euthoracaphis umbellulariae), coconut mealybug (Nipaecoccus nipae), cypress bark mealybug(Ehrhornia cupressi), palm aphid (Cerataphis brasiliensis), whitefly nymphs, and psyllids, such as lemongum lerp psyllid (Cryptoneossa triangula) and redgum lerp psyllid (Glycaspis brimblecombei). Diamond “scale,” which infests palms, is actually the fruiting bodies of a blackish fungus (Phaeochoropsis neowashingtoniae),” according to the CA IPM site.

Scale may be soft or hard bodied and appears as blotches on trees, shrubs and perennial plants. Scale is particularly bothersome on fruit trees and ornamental shrubs. It affects houseplants that have been outside. Sometimes overlooked because of their unusual appearance, some scales do little damage while others reduce growth and vigor of plants. Yellowing leaves are sometimes a symptom of scale. It may also cause wilting.

Controlling Scale

Scale is often controlled by natural predators, if they are not prevented from doing so by the ants. An indirect means of controlling scale without the use of chemicals is to grow some plants that attract beneficial insects and reduce the ant population with baits. A few ants in the garden are not usually a problem, but large infestations enable the multiplication of many pests, including scale. “Place enclosed pesticide baits (insecticide mixed with an attractant) near nests or on ant trails beneath plants.”

While natural enemies may be purchased and released into the problem spots, it is more sustainable to create an atmosphere that attracts them, such as providing shelter, food and water.

The plants sweet alyssum, parsley, dill, and Queen Anne’s lace attract beneficial insects such as lacewings and hover flies. Aphytis, Coccophagus, Encarsia, and Metaphycus species of parasitic wasps are particularly important for controlling scale. Many other flowers and herbs encourage these wasps and other beneficials to come and take up residence. In early spring, plant a few well-placed seeds and seedlings of herbs like yarrow, lavender, tansy, and coriander. A healthy plant is the best defense against mealybug and other pests. Start by planting a healthy, high quality tree or shrub from the trusted professionals at Paradise Nursery. Keep it healthy by following the care instructions we provide. If questions arise, feel free to contact us. Our experienced staff is available to consult, design, install, and manage your landscape and home orchard.