A brown oval barely a quarter of an inch long, tucked against the centre vein on the topside of a leaf: that is soft scale (Coccidae) feeding on the sap of a ZZ plant (Zamioculcas zamiifolia). An infestation is fatal if left alone, but caught early a swab of alcohol or a soap-and-oil spray clears it.
Scale insects feed by sticking their sharp mouthpieces into a leaf vein.
Younger scale insects that are still in their initial stages of life aren’t yet very powerful. They tend to feed around the rims of the leaves and in the space between larger veins. They’re also much smaller and harder to see than adults.
Adults, especially females, usually secure a spot near the center leaf vein. They settle down on the topside of leaves where the fold provides some protection.
Females secrete a waxy cover under which they lay eggs that hatch after two to three weeks. This cover looks like a brown oval about a fourth of an inch (5 mm) long.
These scale insects will also infect other ZZ plant cultivars, like the black zamioculcas raven and the cute Zenzi ZZ plant.
Which treatment for which level of infestation
The right answer depends on how far the scale has gone. Count the brown ovals on your ZZ plant, then pick the matching line below.
Which treatment for which level of infestation
Level of infestation
Treatment
How to apply
A few, caught early
Alcohol on a cotton bud
Swab each scale to dissolve its waxy cover, then rinse or wipe
Scattered over several stems
Water, dish soap, oil and alcohol spray
Spray the mix daily for 3 to 4 days
Plant overrun
Hosing down with water, then the spray
One stem at a time, pot wrapped in a plastic bag
Whichever line fits, act quickly: a single female can start a whole new generation.
How to treat against scale insects
Spray against scale insects
The best recipe is to mix following ingredients:
1 quart (1 liter) of water
1 teaspoon dish soap
1 teaspoon vegetable oil (using neem oil will increase the pest-killing effect)
First, get rid of most of the pests by hosing the plant down with water using a showerhead or low-pressure powerwasher.
Wrap the pot in a plastic bag to protect the root ball and lower stems. Tie a string or rubber band around the stems to close it.
Place this in your bathtub, shower area, or outside in a place that can wet.
Hose the plant down one stem at a time to remove most of the scales with water pressure.
After that, apply the spray as described above.
If the pests are few and sparse
The female’s waxy cover: a brown oval, 5 mm long
Usually, you’ll catch the invasion early on. It’s great to act fast, since a single scale insect can lay hundreds of eggs, and do so multiple times…
Scrutinize your plant with a cotton bud or wad of cotton dipped in high-content alcohol (vodka, gin, or rubbing alcohol work fine). Every time you see a scale insect, swab it over and remove it. The alcohol dissolves its waxy protection.
It’s best to rinse or wipe after applying alcohol to keep the plant healthiest, but usually the quantity is small enough that the plant won’t suffer.
Don’t spill alcohol on the plant. Too much of it, especially if it gets to the roots, would kill the plant!
Written by Gaspard Lorthiois | Loves helping out, especially when it comes to growing things. Worked in herbal medicine, runs a farm, and dabbles in tech. Master's degree and engineer.
