The African milk plant (Euphorbia trigona) is a popular houseplant known for its unique tree-like shape and milky sap. While these succulents are relatively low maintenance, they can still fall victim to some common plant diseases that impact their health. As a grower, it’s important to learn how to identify and properly treat diseases to keep your African milk plant thriving.
Powdery Mildew
Powdery mildew is a fungal disease that presents as a white, powdery growth on leaves, stems, and flowers. It thrives in warm, humid environments with poor air circulation. On African milk plants, powdery mildew often first appears on older leaves as circular white spots that eventually coat the entire leaf surface.
Identifying Powdery Mildew
Look for these signs to confirm powdery mildew:
- White powdery coating over leaves and stems
- Leaf yellowing and eventual leaf drop
- Stunted growth
- Distorted, curled leaves
Treating Powdery Mildew
- Improve air flow around plants
- Remove and destroy severely infected plant parts
- Apply fungicidal soap sprays to control spore spread
- Apply neem oil as a preventative
- Increase sunlight exposure
Catching powdery mildew early and improving growing conditions are key to effective treatment
Root Rot
Root rot is a common African milk plant disease caused by overwatering. Several fungi can cause root rot but all excess moisture. Symptoms include wilting yellowing leaves, and slowed growth as damaged roots struggle to take up water and nutrients.
Identifying Root Rot
- Wilting, drooping leaves
- Leaves turn yellow and drop
- Slowed or stunted growth
- Roots appear brown, mushy, or slimy
Treating Root Rot
- Reduce watering frequency
- Repot plants in fresh, well-draining soil
- Apply fungicide drench to infected roots
- Remove damaged roots before repotting
- Improve drainage and air circulation
Discard any plants with severe root rot. Mild cases can recover with prompt treatment.
Mealybugs
Mealybugs are common sap-sucking pests that feed on African milk plants. They look like small white cottony masses on stems and leaves. Heavy infestations cause yellowing, stunting, and leaf drop. Ants often farm mealybugs for their sugary honeydew secretions.
Identifying Mealybugs
Look for:
- White cotton-like masses on leaves and stems
- Sticky honeydew on plants
- Sooty mold growing on honeydew
- Ants present around plants
Treating Mealybugs
- Remove bugs manually with alcohol swabs
- Apply insecticidal soap sprays directly on bugs
- Release natural predators like ladybugs and lacewings
- Use neem oil to disrupt mealybug growth
- Apply systemic insecticides for heavy infestations
Early detection and using multiple methods lead to the best results against stubborn mealybugs.
Fungal Leaf Spot Diseases
Leaf spots can be caused by different fungal pathogens. Small, circular spots or lesions start on older leaves. Common examples are anthracnose, cercospora leaf spot, and alternaria leaf spot. As spots enlarge, they turn brown or black and leaves yellow and fall off.
Identifying Leaf Spot Diseases
- Small, circular leaf spots in shades of black, brown, gray
- Spots enlarge and turn brown or black
- Yellowing leaves that eventually drop
- Defoliation from bottom up
Treating Leaf Spot Diseases
- Remove and destroy infected leaves
- Apply fungicidal sprays as prevention and treatment
- Avoid overhead watering to reduce spore spread
- Space plants properly to encourage airflow
- Sanitize tools and prune away infected branches
Botrytis Blight
Botrytis blight is a fungal disease that attacks African milk plant flowers and stems. Infected parts develop fuzzy gray mold and collapse into rotted masses. Cool, damp weather promotes outbreaks.
Identifying Botrytis Blight
Look for:
- Gray, fuzzy mold on flowers, stems, and leaves
- Water-soaked spots that enlarge
- Wilted, rotten plant parts
Treating Botrytis Blight
- Remove and discard severely infected parts
- Apply fungicide sprays as both treatment and prevention
- Improve air circulation between plants
- Avoid wetting foliage
- Increase sunlight exposure
Prompt removal of blighted tissue prevents spread to healthy plant parts.
Prevention Is Ideal
While African milk plants can contract certain diseases, the best approach is prevention through proper care:
- Provide optimal sunlight, airflow, watering, and humidity
- Sterilize pots and tools
- Isolate new plants before introducing
- Inspect regularly for early signs of disease
- Address diseases immediately upon detection
Taking these proactive measures reduces the need for intensive treatments down the road. When issues do occur, nontoxic organic solutions are ideal for plant health. With quick identification and treatment, many African milk plant diseases can be successfully managed.
African Milk Tree Care
Caring for an African milk tree is easy, and is similar to caring for the typical cactus. The main issues are overwatering.
Soil: Loose, well-draining soil that is moderately fertile.
Temperature: Can withstand temperatures down to frost (= 32 degrees) for a short period of time.
Water: Occasional, deep watering. Allow the soil to completely dry out between waterings. Either use a moisture meter or stick your finger through the soil to gauge the moisture level. It’s better to err on the side of underwatering than overwatering.
Sun: Full sun in temperate regions. Partial shade in the Palm Springs area.
Euphorbia trigona Rubra, also named Euphorbia trigona Royal Red’ for sale at the nursery
African Milk Tree Appearance
Up close look at African Milk Tree
Very distinct shape. Stems are formed of three sides (hence the name trigona), have unusual, small leaves shaped like teardrops growing from the sides, and many small, sharp spines.
Although commonly seen as a small to medium-sized container plant with a handful of stems, eventually, numerous stems will grow into a dense thicket. This growing pattern is perhaps why its called a tree, although its a succulent. A main woody “tree trunk” will develop as it matures. Stems have a vertically growing habit.
African milk trees can grow to 10 feet tall given favorable conditions. Indoors, it often grows to 6 feet or so.
The stems and branches are dark green which becomes brighter with more light. Euphorbia trigona Rubra, also named Euphorbia trigona Royal Red, is a variety that features both the green and magenta-purple hues. Beautiful, vibrant color on both varieties.
Leaves drop during the dormant season and regrow at the start of the growing season. In conditions in which the light intensity and temperature do not fluctuate much, leaves may stay on for longer than a year.
Identifying and Treating Common Plant Diseases
FAQ
What is the disease in the African Milk Tree?
What are the pests of the African Milk Tree?
How do you treat African Milk Tree sap on skin?
How do you care for African milk tree?
African Milk Tree is relatively hardy and resistant to disease and pests as long as it is well cared for. You can also use a paper towel and rubbing alcohol to remove bugs or spray off the bugs with water from a garden hose. Avoid waterlogging the soil and provide the plant with good sunlight and air circulation.
Can African milk tree rot?
If left untreated, root rot on your African milk tree (Euphorbia trigona) can be fatal. For this reason, if the symptoms appear, we highly advise that you adhere to our recommendations to keep your plant alive: Blackened and softened roots. Why does my African milk tree have gray mold spots?
Do African milk trees have pests?
Pests that can affect an African Milk Tree include spider mites, mealybugs, whiteflies, or scale. If you notice any of these pests on your plant, treat them immediately with a pesticide or insecticidal soap. If you notice any of the following signs on your African Milk Tree, the tree likely has pests:
Why is my African milk tree dying?
Incorrect watering tends to be the most common reasons for dying african milk trees. It’s easy to get the watering frequency and volume wrong as how much water a african milk tree needs will be different per season. Generally speaking, african milk trees need to be watered once a week.