Quick Guide: African Violet Diseases and Insect Pests
Affected Plants: African violet (Saintpaulia spp.)
Primary Disease Types: Crown and root rot, Botrytis blight
Primary Insect Pests: Cyclamen mites (Steneotarsonemus pallidus), mealybugs (Planococcus citri, Pseudococcus comstocki)
Primary Causes: Excessive watering, poor drainage, high humidity, contaminated potting media, pest infestations
Most Important Prevention Strategy: Maintain proper watering practices, use sterile potting media, and provide good sanitation.
Chemical Control: Insecticidal soaps, neem oil, pyrethrins, sulfur products, cyfluthrin, imidacloprid, and labeled miticides.
African violets are one of the most popular flowering houseplants in America. Their popularity stems from their ease of growth and their ability to bloom for 10 to 12 months of the year.
The most common African violet diseases and insect pests can usually be prevented through proper cultural care and sanitation. For more information about growing African violets, visit African Violet (HGIC 1550).
African Violet Diseases: Crown and Root Rot on African Violet
Crown and root rot is one of the most serious fungal problems affecting African violets.
Cause
Crown and root rot is caused by several soilborne water molds, primarily Pythium spp and Phytophthora spp, especially when plants are:
- Watered excessively
- Have poor drainage
- planted too deeply
Symptoms
- Crown turns soft and mushy
- Roots turn soft and mushy
- Older leaves droop
- Younger leaves in the center of the plant appear stunted
- Young leaves turn black and die
Prevention & Control
Cultural Controls
- Always use sterilized potting soil mixes when planting
- Use clean containers when planting
- Do not plant African violets too deeply
- Discard severely affected plants
When reusing containers from infected plants:
- Scrub pots thoroughly
- Soak reused pots for 30 minutes in a 1 part household bleach to 9 parts water solution
Resistant Varieties
None available
Biological Control
None available
Chemical Control
None available
African Violet Diseases: Botrytis Blight on African Violet
Botrytis blight is a fungal disease that can affect leaves, stems, and flowers of African violets.
Cause
Botrytis blight is caused by the fungus Botrytis cinerea.
Symptoms
Botrytis blight often first appears as small, water-soaked lesions on the underside of the leaf. Symptoms may include:
- Small water-soaked lesions on the underside of leaves
- Blighted leaves
- Blighted stems
- Blighted flowers
- Dark brown to gray discoloration
- Fuzzy coating on affected plant parts
Prevention & Control
Cultural Controls
- Collect and discard all dead and dying plant material.
- Provide better air circulation.
- Avoid getting the flowers and foliage wet.
Botrytis often follows mite injury, so controlling mites helps control this disease.
Resistant Varieties
None available
Biological Control
None available
Chemical Control
None available
African Violet Insect Pests: Cyclamen Mites on African Violet
Cyclamen mites are one of the most serious pests affecting African violets.
Cause
Cyclamen mites (Steneotarsonemus pallidus) are extremely small mites (approximately 1/100 inch long) that feed on new growth (i.e., leaves in the center of the plant).
During feeding, they inject a toxic chemical that disrupts normal growth patterns.
Cyclamen mites develop most rapidly with high humidity (80 to 90 percent) and cool temperatures at or near 60°F.
To avoid light, they favor the plant crown or leaf folds where the petiole (stalk that attaches the leaf to the stem) joins the stem. As such, damage is usually first seen there.
Symptoms
Damage to plants is often the first indication of a cyclamen mite infestation. Symptoms may include:
- Severe stunting of leaves in the center of the plant
- Leaf curling
- New leaves that are very hairy and appear grayish
- Stunted flower buds
- Misshapen flowers even fail to open
- Flower buds that fail to open
- Death of leaf buds
- Death of flower buds
- Death of the center of the plant
- Death of the entire plant in severe infestations
Even after infestations are controlled, some symptoms may remain. A return to normal appearance requires time and gradual pruning of distorted leaves.
Prevention & Control
Cultural Controls
- Space plants so that they do not touch
- Avoid touching infested plants before working with non-infested plants
- Isolate infested plants
- Discard badly infested plants
For pots from discarded plants:
- Thoroughly scrub the pots clean
- Soak pots for 30 minutes in a solution of 1 part household bleach to 9 parts water
Resistant Varieties
None available
Biological Control
None available
Chemical Control
For valuable plants, spray with a miticide that is labeled for use on houseplants. Take the plant outside during mild temperatures and spray with:
- Insecticidal soap
- Sulfur products
- Tau-fluvalinate products
Two or three sprays at three-day intervals may be required for mite control.
See Table 1 for examples of brands and products. Follow label directions for use and safety of all products.
African Violet Insect Pests: Mealybugs on African Violet
Several species of mealybugs can feed on African violets, causing distorted growth and plant decline.
Cause
Several kinds of mealybugs are pests on African violets, including:
- Citrus mealybug (Planococcus citri)
- Comstock mealybug (Pseudococcus comstocki)
Mealybugs are about ¼ inch long and have soft bodies covered with a white, waxy material that gives them a cottony appearance.
They are found on leaves, stems, and leaf crotches, where they feed by sucking plant sap.
Symptoms
Mealybug feeding may cause:
- White, cottony masses on leaves, stems, and leaf crotches
- Stunted leaves
- Distorted leaves
- Sticky leaves coated with honeydew
- Leaf death during heavy infestations
- Plant death during heavy infestations
As they feed, they excrete honeydew, a sugary material that can coat the leaves and make them sticky.
Prevention & Control
Cultural Controls
- Inspect new plants carefully before bringing them indoors
- Check the bottom of the pot for mealybug eggs
- Remove light infestations with a cotton swab dipped in rubbing (isopropyl) alcohol
- Repeat alcohol treatments as needed
Resistant Varieties
None available
Biological Control
None available
Chemical Control
Heavy infestations are more difficult to control because the waxy covering protects adult mealybugs from insecticides. The immature nymphs are susceptible to treatment.
Houseplant insect sprays that may be used include:
- Insecticidal soap (naturally-derived)
- Pyrethrins (naturally-derived)
- Acetamiprid (synthetic)
- Cyfluthrin (synthetic)
- Imidacloprid (synthetic)
For spray applications:
- Take the plant outside during mild temperatures before spraying.
- Two or three sprays at three-day intervals may be required.
Alternatively, soil-applied insecticide granules containing imidacloprid may be used.
See Table 1 for examples of brands and products containing these active ingredients. Follow label directions for use and safety of all pesticides.
Other Problems on African Violet: Failure to Flower
Failure to flower on African violet is commonly associated with unfavorable environmental conditions.
Cause
African violet flower buds may fail to open, turn brown, and fall off. Unfavorable environmental conditions such as low temperatures, poor soil aeration, wet soil, or excessively dry air contribute to flower failure.
Blossoms will drop if there is the slightest presence of cooking gas.
Symptoms
- Flower buds fail to open
- Flower buds turn brown
- Flower buds fall off
- Blossoms drop prematurely
Prevention & Treatment
Cultural Controls
Avoid environmental conditions that contribute to flower failure, including:
- Low temperatures
- Poor soil aeration
- Wet soil
- Excessively dry air
- Exposure to cooking gas
Chemical Control
None available
Other Problems on African Violet: Petiole Rot on African Violet
Petiole rot in African violets is a physiological disorder, not a disease.
Cause
A rust-colored spot may appear where the leaf stem touches the pot. This problem is not a disease; it occurs when fertilizer salts accumulate on the rim of the pot and the soil surface.
Symptoms
- Rust-colored spot where the leaf stem touches the pot
Prevention & Treatment
Cultural Controls
- Avoid over-fertilization
- Use a salt-free water source, such as rainwater
- Place tape or foil on the rim of the pot
- Flush the container with plenty of freshwater to leach salts from the soil
Chemical Control
None available
Other Problems on African Violet: Water Spots on African Violet
Water spots on African violet are caused by contact with cold water.
Cause
Yellow or white ring and line patterns on African violet leaves are caused by contact with cold water.
Symptoms
- Yellow ring patterns on leaves
- White ring patterns on leaves
- Yellow line patterns on leaves
- White line patterns on leaves
Prevention & Treatment
Cultural Controls
- Keep leaves dry when watering
Table 1: Insecticides and Miticides for African Violet Pests
The following insecticides and miticides are listed in the source document for management of cyclamen mites, mealybugs, aphids, whiteflies, and other pests that may occur on African violets. Always read and follow all label directions before using any pesticide.
Natural and Less-Toxic Insecticides & Miticides
Active Ingredient |
Example Product Names |
Pests Controlled |
| Insecticidal Soap | Bonide Insecticidal Soap Multi-purpose Insect Control Ready to Use Garden Safe Brand Insecticidal Soap Insect Killer Miracle-Gro Nature’s Care Insecticidal Soap Natria Insecticidal Soap Ready-to-Use Natural Guard by ferti-lome Insecticidal Soap Concentrate Safer Brand Insect Killing Soap Concentrate II Whitney Farms Insecticidal Soap 1 |
Mites, mealybugs, aphids, whiteflies |
| Neem Oil | Bonide Captain Jack’s Neem Oil Concentrate Bonide Captain Jack’s Neem Oil Ready to Use Bonide Rose Rx 3-in-1 Concentrate Bonide Rose Rx 3-in-1 Ready to Use Garden Safe Fungicide 3 Garden Safe Fungicide 3 Concentrate Garden Safe Neem Oil Extract Concentrate Monterey 70% Neem Oil Fungicide/Insecticide/Miticide Natria Neem Oil Concentrate Natria Neem Oil Ready-to-Use Natural Guard Brand by ferti-lome Neem Safer Brand Neem Oil Concentrate Fungicide/Miticide/Insecticide Safer Brand Neem Oil RTU Fungicide/Miticide/Insecticide Southern Ag Triple Action Neem Oil |
Mealybugs, aphids, whiteflies, mites |
| Pyrethrins & Neem Oil | Ferti-lome Triple Action Monterey Fruit Tree Spray Plus Monterey Rose & Flower Spray Plus |
Mites, mealybugs, aphids, whiteflies |
| Pyrethrins Neem Oil Insecticidal Soap | Safer Brand EndALL Insect Killer | Mealybugs, aphids, mites, whiteflies |
| Pyrethrins & Sulfur | Bonide Captain Jack’s Orchard Spray Concentrate Bonide Captain Jack’s Orchard Spray Ready to Spray Bonide Captain Jack’s Tomato & Vegetable Ready to Use Natria Insect, Disease & Mite Control Ready-to-Spray Natria Insect, Disease & Mite Control Ready-to-Use Natria Rose & Flower Ready-to-Use Insect, Disease, & Mite Control Ortho Insect, Mite & Disease 3-in-1 Ready to Use Whitney Farms 3-in-1 Rose & Flower Care |
Mites, mealybugs, aphids, whiteflies |
| Pyrethrins & Canola Oil | Monterey Take Down Garden Spray | Mealybugs, aphids, whiteflies, mites and thrips on foliage |
| Cottonseed Oil
Clove Oil Garlic oil |
Bonide Mite-X Ready to Use | Mites, aphids, thrips |
| Rosemary Oil,
Clove Oil, & Cottonseed Oil |
Monterey All Natural Mite & Insect Control RTU | Spider mites, whiteflies, aphids, scale crawlers, mealybugs |
| Pyrethrins | Bonide Bon-Neem II Fungicide/Miticide/Insecticide Ready to Use Bonide Japanese Beetle Killer Ready to Use Ferti-lome Fruit Tree Spray With Neem Py Garden Safe Brand Multi-purpose Garden Insect Killer Garden Safe Brand Rose & Flower Insect Killer Garden Safe Houseplant & Garden Insect Killer Ortho Tree & Shrub Fruit Tree Spray ConcentrateSouthern Ag Natural Pyrethrin A Botanical Concentrate |
Mealybugs, aphids, whiteflies (only lasts for a few hours) |
| Rubbing Alcohol (70% isopropyl
alcohol) |
Multiple brands (applied with cotton swabs, such as Q-Tips) | Mealybugs, aphids, whiteflies, scale crawlers |
Contact & Systemic Insecticides
Active Ingredient |
Example Product Names |
Pests Controlled |
| Cyfluthrin | BioAdvanced Science-Based Solutions Rose & Flower Insect Killer Ready-to-Use | Scale crawlers, aphids, mealybugs, whiteflies, beetles and caterpillars |
| Imidacloprid | Bonide Systemic Houseplant Insect Control Granules Hi Yield Systemic Insect Granules |
Mealybugs, aphids, whiteflies, leaf miners, thrips, beetles, scale crawlers, mites |
RTU = Ready to Use (a small, pre-mixed spray bottle)
Note: Spraying houseplants is safest outdoors, in the shade, during mild temperatures. Once plants are dry, they may be brought back indoors.
Granular products are sprinkled on the soil surface and watered in.
Pesticides are updated annually.
Frequently Asked Questions About African Violet Diseases and Insect Pests
Why are my African violet leaves turning black?
Blackened young leaves may be a symptom of crown and root rot.
Why are my African violet flower buds not opening?
Low temperatures, wet soil, poor aeration, and excessively dry air may cause flower buds to fail to open.
What causes sticky leaves on African violet?
Mealybugs excrete honeydew, which can coat leaves and make them sticky.
The last updates were made on 06/26 by N. Jordan Franklin.
Originally published 05/99
