As hairy as your African violet leaves are, they don't have dandruff! If you notice white cotton-like specks on them, they are most likely infested with leaf mealy bugs. In addition to leaf mealy bugs, which feed on the leaves, you should also check frequently for soil mealy bugs that feed on the roots of your Saintpaulis.
At the first sign of infestation by either type of mealy bug, it is very important to quarantine infested plants. Although soil mealy bugs don't spread as quickly as leaf mealy bugs do, plants that share a common watering tray are susceptible to infestation by both.
How to kill leaf mealy bugs
Leaf mealy bugs are also known as foliar mealy bugs or cottony mealy bugs. They are tiny- typically measuring 1/16 to 1/4 inch in length. Most commonly seen on the undersides of the leaves, they also infest the axils of the leaf and the crown of the plant.
Before you spot the leaf mealy bug, you might first see a change in the leaves of your African violet. Stickiness, wilt, color fading, and sooty mold (which shows up as dark specks on the tops of the leaves) may all be signs of leaf mealy bug infestation.
Although light infestations of leaf mealy bugs can be curtailed by swabbing the leaves with a cotton swab doused with Isopropyl rubbing alcohol (70%), for heavier infestations, you need to apply Acephate or Malathion.
How to kill soil mealy bugs
Soil mealy bugs, also called "blind", "Pritchard", and "root" mealy bugs, are full grown at just 1/16 inch and look like small grains of rice that cling to the roots of your Saintpaulis. It's typical for them to feed at the top of the root ball on the newest feeder roots of your plants.
Because they attack the roots of your African violet, soil mealy bugs inhibit your plant's ability to absorb the nutrients and moisture it needs for growth, resulting in the main symptom of infestation, slow growth of your African violet. In heavy infestations, you may see soil mealy bugs clustered about the main stem of your plant above the soil.
Traditional treatment for soil mealy bug infestation is application of Acephate or Malathion. Treatment should be daily and may take four or five days.
An ounce of prevention…
The best way to guard against mealy bug attacks is to isolate any new plants you bring into your home until you are positive there is no infestation. Afterwards, be sure to examine leaves and stems every time you water your African violets.
Mixing your African violet potting soil with a teaspoon of diatomaceous earth (DE) per liter of mix is also a good preventative and combatant against soil mealy bug infestations. DE is the skeletal remains of single celled plants (diatoms) that lived in prehistoric oceans. An effective natural insecticide, there is no chemical hazard in using DE. On the contrary, full of trace minerals, DE is beneficial to the soil.
Although our domestic cultivars don't tower to 300 feet like their wild relatives, the African violet with its many hybrids, bright colors, and cheerful disposition tops the list of many indoor container gardeners. Given a good start, a single Saintpaulis adds to indoor container gardening enjoyment with years of continuous bloom and dozens of new easily propagated plants.
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