Cottony cushion scale inspires a certain measure of fascination. One look at these intricate insects, and you’re sure to want to learn more.
Cottony cushion scale (Icerya purchasi) are soft scale insects. Like other scale insects, their lifecycle touches on the bizarre. But before we get started, take a look at this photo and see if you can figure out what, exactly, is insect and what might be something else.
Cottony cushion scale lifecycle
Cottony cushion scale insects start out as eggs. The eggs hatch out into crawlers. First stage (instar) crawlers are red, with black legs and antennae. These newlings make their way to nearby leaf veins, where they will begin producing their telltale white, cottony secretion. As they grow, these tiny pests will shed their outgrown skins (molt) and grow a bigger protective coating. Second instar crawlers make their way to twigs and leaves. Third instars prefer branches. Adults are usually found on branches and tree trunks.
Nearly every cottony cushion scale insect you see will be female, and they tend to form colonies. The males have red wings, but are really too small to see. Females can produce young with or without the help of a male. She will lay 600 to 800 eggs. Before she does, she will carry them around in a white, fluted sac that can be 2 or 3 times the length of her body. Most people mistake this egg sac for the insect’s body. Did you?
Damage caused by cottony cushion scale
Scale insects feed by inserting tiny, straw-like structures into bark, leaves, or fruit. One attached, they will suck the sugary juices out of fruit, or mainline sap directly from the xylem. This high sugar diet results in the insects pooping out honeydew, an equally sweet, high nutrient discharge that ants and fungi just love. Heavy infestations can lead to overall stress and loss of vigor, branch dieback, and defoliation of affected areas. Very often, it is the presence of sooty mold and heavy ant traffic that will first cue you to the presence of scale insects.
How to control cottony cushion scale
Natural predators do a much better job of controlling these pests than we do. Specifically, the vedalia beetle (Rodolia cardinalis) and the parasitic fly (Cryptochaetum iceryae) feed only on this particular pest and nothing else. Normally, these two beneficial insects are all that is needed to control a cottony cushion scale infestation. Unfortunately, dust, ants, and insecticides can interrupt that assistance.
'Ants will actively protect and farm scale insects. You can remove that protection by attaching sticky barriers around the trunks of trees. Chemical controls are not generally effective against cottony cushion scale insects (regardless of what they say on the label).
Take a look at your trees on a regular basis to see if cottony cushion or other scale insects have set up shop in your garden or foodscape.
You can grow a surprising amount of food in your own yard. Ask me how!