White Cotton Spots & Worms on Leaves

Cottony Cushion Scale

• The cottony cushion scale (Icerya purchasi) is characterized by a white cotton egg sac attached to its body. The adult female crawls across leaves and twigs with its orange, yellow or brown body. Between 600 and 800 red eggs are held in the white cotton egg sac that typically extends two to three times longer than the body of the cottony scale itself. A small insect, the total length of the scale and the egg sac combined is approximately 1/2 inch.

Skin and Cocoons

• More cotton spots and worms on leaves begin to display when the eggs of this scale hatch and larvae begin to feed on the foliage. These immature, red crawlers with black legs and antennae secrete a white cottony substance, then shed their skin, leaving behind what appears to be a collection of white cotton balls on the leaves. In addition, white cottony cocoons house the male cottony cushion scale. These structures are usually found on the ground or are well hidden within nooks and crannies of the tree.

Mealybug

• Mealybugs look like white cotton balls on the leaves of a plant. They are covered by a waxy collection of white strands and powder. The mealybugs themselves measure approximately 1/4 inch in length while the white filaments that grow from their body typically jut outward more than 1/2 inch, giving the oval body of the mealybug a distinct, fluffy appearance. The insect remains in one spot on the leaf for the entirety of its 4- to 10-week lifespan.

Mealybug Control

• The mealybug feeds on the plant by sucking sap from the leaves, often damaging the specimen to the point that it dies. Plants that are only lightly infested will suffer a yellowing of the leaves and loss of vigor while the black fungus called sooty mold also develops, a result of the honeydew excrement left behind, courtesy of the mealybugs. Picking off the mealybug and eggs sacs will minimize the population on small plants while insecticides are available for use on trees.