Mealybugs and Scales

Marijuana Horticulture

by Jorge Cervantes

Identify Mealybugs

Somewhat common indoors, these 0.08-0.2 inch oblong, waxy white insects move very little, mature slowly, and live in colonies that are usually located at stem joints. Like aphids, mealybugs excrete sticky honeydew.

Identify Scales

As common indoors as mealybugs, scale looks and acts similar to mealybugs but is usually more round than oblong. Scales may be white, yellow, brown, gray, or black. Their hard protective shell is 0.08-0.15 inch across. Mealybugs rarely or never move. Check for them around stem joints where they live in colonies. Scales sometimes excrete sticky honeydew.

Damage

These pests suck sap from plants which causes growth to slow. They also exude sticky honeydew as a by-product of their diet of plant sap which encourages sooty mold and draws ants that eat the honeydew.

Controls

These pests present little problem to indoor growers. The easiest and most efficient control is listed under Cultural and physical below.

Cultural and physical control

Manual removal is somewhat tedious but very effective. Wet a Q-tip in rubbing alcohol and wash scale away. A small knife, fingernails, or tweezers may also be necessary to scrape and pluck the tightly affixed mealybugs and scales after they are Q-tipped with alcohol.

Biological

There are numerous species of mealybugs and scales. Each has natural predators including species of ladybeetles (ladybugs) and parasitic and predatory wasps. There are so many species of each that it would be exhaustive to lit them here.

Sprays

Homemade sprays that contain rubbing alcohol, nicotine, and saps all kill these pests. Insecticidal soap, pyrethrum, and neem oil are all recommended.