There are all sorts of strange things we discover while caring for houseplants. One of the most perplexing is the appearance of white sticky stuff on plant leaves.
Spotting this unusual yuk might spark curiosity, but it warrants immediate action.
If not treated immediately, the sticky stuff is a sign of a significant problem. It can lead to more health risks for your plants.
Other conditions can create a clear sticky substance or leave a powdery white residue.
When the substance is both white and sticky, it means you have a particularly nasty infestation on your hands.
What Plant Bugs Cause The White Sticky Stuff on Plants?
The white sticky spots on plants is actually a case of sap-feeding insects in action.
The white, fuzzy, or lumpy part is a type of common scale known as mealybugs. They have a close relative, cottony cushion scale (which can be treated in the same way as mealybugs).
Plant scale comes in a range of colors. Mealybugs are white and tend to look like tiny bits of cotton.
The mealybugs produce a protective waxy coating lending to some of the stickiness, rendering the adults immobile.
When mealybugs pierce the plant to drink its fluids, some of this sap, along with mealybug excrement, is left on the surface. This clear, sugary goo is known as honeydew.
What Damage Does It Cause To Infected Plants?
Mealybugs feed off of plant sap, which is your houseplant’s equivalent of blood.
Their mouthparts are designed to pierce the plant’s outer surface into the pressurized veins. This often causes some of the plant juices to spurt out or even pass through the mealybug’s body without a chance to digest it.
This contributes to the sticky plant leaves and the amount of honeydew left on the plant surface.
The feeding process removes vital chlorophyll from the leaves and stems of plants. This causes those parts to turn yellow, then brown, and become brittle.
A single mealybug will have no effect on one plant. But, their habit of hiding on the undersides of leaves, in joints and crevasses, means a colony can spring up fast before you spot the first one.
Honeydew, is a prime breeding ground for fungal infections and a catalyst for sooty mold.
It attracts other pests, such as ants, who use honeydew for food.
On outdoor plants, the honeydew distracts bees, which will make honey using the honeydew instead of pollen. This causes the colony to suffer from malnutrition and reduce plant pollination.
Related: Fuzzy White Aphid Bugs
Pest Control Methods For Mealybug Infestations
There are several natural methods of control to get rid of mealybugs, and they all have the same initial steps.
The moment you spot an infestation of mealybugs on one of your plants, isolate it and any nearby plants.
This can be difficult or impossible for outdoor plants. Stronger treatment methods at more frequent intervals may be needed.
Use sterile tools. Keep a container of isopropyl alcohol on-hand to clean the pruning tools frequently.
Carefully isolate each infected leaf and trim it off. Place it immediately in a sealable plastic bag.
In the case of a recently infected plant, this will often get rid of most of a light infestation.
If a plant has a severe infestation start treating with neem oil or horticultural oil.
Be sure to wash your hands after any contact with an infected plant.
Dipping a cotton swab in rubbing alcohol is a good way to kill individual mealybugs.
The alcohol destroys their wax shell on contact. The alcohol cotton ball method is not for heavy infestations.
Bathing Your Plant
One of the simplest treatment methods is to bathe your plant.
Mix mild dish soap or insecticidal soap with water. Fill a sprayer with the mixture and soak every part of the plant. Take extra care to get under the leaves and any joints.
The spray will dislodge the mealybugs and even kill them and insecticidal soap won’t leave a residue. Repeat the process several times over a week to ensure any hatched eggs have been killed.
Horticultural and Neem Oil
Organic Neem pesticide is one of the best natural options for pest control. Wipe your plant down with it or use in a sprayer.
Coat the entire plant. This not only kills the mealybugs and other pests but will keep your indoor plants shiny and healthy.
When dealing with outdoor infestation of scale on plants, use neem oil’s big brother, horticultural oil.
Safe and natural, horticultural oil is easier to use on trees and large shrubs while providing the same benefits as neem oil.
Be aware, both of these options can affect beneficial and predator insects. Try to avoid coating any blooms when treating outdoor flowering plants.
Pesticides & Insecticides
When dealing with a larger plant or outdoor infestations, a pesticide or insecticide may be necessary.
Choose a product labeled to kill mealybugs on contact and follow the directions carefully.
These products often require more than one application before the infestation is eliminated.
Be aware that insecticidal treatments will often affect honeybees. It’s best to avoid using them on blooming outdoor plants.
Bonus Tip: Mealybugs and Soil
Mealybugs are able to survive in soil, leading to the single most common cause of repeat infestations. There are many different ways to solve this problem, such as replacing the top few inches of soil and drenching soil with neem oil.