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Past Articles Library | Organic Pest Control | Soft Brown Scale

SOFT BROWN SCALE
(Coccus hesperidum)

Attacks a wide variety of field, ornamental, houseplants, and greenhouse plants; a world-wide problem.

DESCRIPTION

Adult Females are wingless bumps that are oval or round, soft, and legless, 1/10 to 1/5 inch (2.5-5 mm) in size. Adult males are very small, almost minute, with yellow wings. Early-stage larvae are called "crawers" and look like miniture mealybugs; as they grow older, they become immobile.

LIFE CYCLE

Females of some species lay as many as 2,000 eggs; other species can give birth to several nymphs each day. Nymphs are mobile for a short time and then they settle down and the females molt into an immobile form. They can have 1 or 2 generations per year outdoors, and up to 6 generations on indoor plants.

PLANTS MOST AFFECTED

Citrus, many fruits and houseplants, various ornamental trees and shrubs.

DAMAGE

This is a piercing-sucking insect that sucks plant sap at all stages of its development, causing leaves to yellow and die. In severe infestations, plants will die. Soft brown scale secrete a sticky clear substance known as "honeydew" which provides the ideal environment to a fungus called "sooty mold" which can be more damaging than the scale itself. Sooty mold blackens the leaf, decreases photosynthesis activity, decreases vigor, and often causes disfigurement of the host plant. When the sooty mold occurs on fruit, it often becomes unmarketable or of a lower grade, as the fungus is difficult to wash off.

MEANS OF CONTROL

Adult scales are protected from insecticides or sprays by waxy coverings, so spray control measures should be aimed at unprotected immatures (crawlers). Spot treatments should be applied when scales are present. Applications of insecticidal soap or horticultural oil will kill scales, but at least three treatments are needed to control an infestation. Repeat every six to seven days until scales have been eradicated. Dead scales do not fall from plants, so you'll have to examine plants to determine whether the scales are dead or alive. Crush the scale - if it's dry, the scale is dead; if the body is juicy or leaves a streak when smeared on a piece of paper it was alive.