African violets (Saintpaulia ionantha) are popular flowering houseplants in America, prized for their ease of growth and long blooming period. However, like many houseplants, they are susceptible to various pests, including mealybugs. Mealybugs are common pests of houseplants.
If you see what look like small bits of cotton on African violets, the plant has mealybugs, sucking insect pests, not a disease. This article will guide you through identifying and treating mealybugs on your African violets, ensuring your plants remain healthy and vibrant.
Mealybugs on houseplants (Source: extension.umd.edu)
Identifying Mealybugs
Several kinds of mealybugs are pests on African violets, including the citrus mealybug (Planococcus citri) and the Comstock mealybug (Pseudococcus comstocki). Mealybugs are small soft-bodied insects that are 1/20 to 1/5 inch in size.
Here are the key characteristics to look for:
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- Appearance: They have soft bodies and are covered with a white waxy material that makes them look cottony.
- Location: Mealybugs are found on leaves, stems, and leaf crotches. They damage plants by sucking out their sap. Root mealybugs may not be noticed unless you look directly at the root ball.
- Signs of Infestation: Sometimes there are obvious signs of an infestation, such as stunted or distorted leaves. But often the plant just doesn't look healthy.
Mealybugs are sometimes confused with other pests that also produce waxy coatings such as scale, aphids, and whiteflies.
Types of Mealybugs
- Citrus Mealybug (Planococcus citri): The most common species found on plant foliage.
- Longtailed Mealybug (P. longispinus): Named for the tail filaments that develop on this species. The longtailed mealybug does not lay eggs but produces live young, similar to aphids.
- Ground Mealybug (Rhizoecus falcifer): The most common soil mealybug, occurring on the roots of many house plants, especially African violets.
Mealybug damage on plant (Source: www.planetnatural.com)
Symptoms of Mealybug Infestation
Mealybugs feed by extracting sap from plants, causing damage to plant tissue.
Common symptoms include:
- Stunted or distorted leaves
- Yellow or wilted leaves
- Deformed growth
- Loss of flower buds
- Defoliation
- Chlorosis
Their feeding causes stunted and distorted leaves. Heavy infestation can cause leaf and plant death. Citrus mealybugs inject a toxin while feeding that causes plant malformation.
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Additionally, mealybug excretions can lead to sooty mold, interfering with photosynthesis.
Causes and Prevention
Mealybugs are most often introduced from infested greenhouse-grown plants purchased at a nursery or garden center. They may also be found in potting soil or on grocery store produce.
Prevention is key to managing mealybugs. Here are some tips:
- Carefully inspect all new houseplants before introducing them to your home, and keep them separate from other plants for a week or so if possible.
- Check under leaves, in new leaf folds, and around the growing tips for signs of infestation.
- Maintain a clean greenhouse and growing area free of debris and old plant material.
- Avoid nitrogen-rich fertilizer and overwatering as nitrogen stimulates tender new growth that mealybugs prefer, and may lead to increased egg production.
Treatment Methods
Mealybugs are difficult to get rid of because immatures typically wedge themselves in stem crotches, leaf folds, or other tight locations where washing or pesticides cannot reach them.
Here are several methods to control mealybugs on your African violets:
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Non-Chemical Treatments
- Washing Plants: A moderately strong spray of warm water will dislodge most of the mealybugs.
- Rubbing Alcohol: Wipe the insects and egg masses off the plants with a cotton swab or cloth dipped in rubbing alcohol. This is most effective on large-leaved plants. Test first on a small area to make sure the alcohol won’t damage the plant; it may take a day or two for symptoms to show.
- Pruning: Prune out heavily infested plant parts when such pruning won’t damage the appearance of the plant. Dispose of plant cuttings immediately, since mealybugs can survive on detached plant parts for as long as those parts have moisture.
- Diatomaceous Earth (DE): Add diatomaceous earth (DE) to the fresh soil. Please note, DE may help with an early infestation, they do not completely kill off the adult Soil Mealy Bugs, they may kill off a nymph.
Chemical Treatments
- Insecticidal Soap: Less toxic alternatives such as insecticidal soap or horticultural oils can be effective, but must be applied to the hard-to-reach places the mealybugs inhabit to kill the insects. These may require several applications to achieve control.
- Horticultural Oil: Neem oil is a natural remedy derived from the neem tree. The oil will coat and suffocate eggs, nymphs and adults. Repeat treatment as needed.
- Registered Insecticides: There are several registered insecticides available at garden centers that will control mealybugs.
Biological Control
A number of natural enemies, including several parasitic wasps and predators, are known to attack mealybugs. The mealybug destroyer, Cryptolaemus montrouzieri, is a small lady beetle that is a very effective predator, especially when mealybug numbers are high and many egg masses are present.
Table 1. Examples of Brands and Products for Mealybug Control
| Active Ingredient | Example Brands/Products |
|---|---|
| Insecticidal Soap | Safer's Insecticidal Soap |
| Neem Oil | Neem Oil products |
| Acetamiprid | Houseplant insect sprays with acetamiprid |
| Cyfluthrin | Houseplant insect sprays with cyfluthrin |
| Imidacloprid | Soil-applied insecticide granules containing imidacloprid |
Additional Tips for African Violet Care
Maintaining healthy African violets involves more than just pest control. Here are some essential care tips:
- Lighting: Bright light is needed, but it cannot be direct sunlight. African violets like a north, northwest, or northeast-facing window. Place the plant a good three feet away from a south-facing window.
- Watering: Water your African violet when just the top of the soil is dry, but before it becomes hard and crusty or the plant wilts. Avoid getting the leaves wet during watering. If water remains in the bottom saucer an hour after watering, you should drain this off.
- Fertilizing: African violets require fertilizing on a regular basis. Use a fertilizer that is specially formulated for African violets, as it will provide the proper balance of nutrients.
- Humidity: Proper humidity can make a difference in the health of your plants. If your home has dry heat, a small humidifier near the plants may be helpful. Setting a tray of pebbles and water nearby can raise the humidity.
African violet in bloom again. Staying on top of mealy bugs!
By following these guidelines, you can effectively identify, treat, and prevent mealybug infestations, ensuring your African violets thrive and continue to bring beauty to your home.
