Calathea is a genus of tropical flowering plants known for their striking foliage and vibrant patterns. While these plants are prized for their ornamental qualities, they are not immune to pests and diseases. Proper care and maintenance are essential to keep your Calathea plants healthy and thriving. Here are some common pests and diseases that can affect Calathea plants:
Spider Mites: Spider mites are tiny arachnids that feed on plant sap, causing stippling, discoloration, and webbing on the leaves. Calathea plants are susceptible to spider mite infestations, especially in dry indoor conditions. Regularly misting your plants and keeping the humidity levels up can help deter spider mites. Refer to a previous discussion of how we here at Sunshine Horticulture manage these little pests.
Mealybugs: Mealybugs are soft-bodied insects that can cluster on the undersides of Calathea leaves and in the leaf axils. They feed on plant juices and excrete a sticky, sugary substance called honeydew. This can lead to the growth of sooty mold on the leaves.
Aphids: Aphids are small, soft-bodied insects that often congregate on new growth, such as the tender leaves of Calathea plants. They can deform leaves, cause yellowing, and transmit viruses.
Scale Insects: Scale insects are another common pest of Calathea plants. They form hard, protective shells that make them appear like small, immobile bumps on the stems and leaves. Scale insects feed on plant sap and can weaken the plant over time.
Fungal Leaf Spot: Often caused by species of the Colletotrichum or Cercospora fungi, Fungal Leaf Spot can appear as dark or brownish spots with a yellow halo on the leaves of Calathea plants. These spots can grow in size and lead to leaf damage. Avoid overwatering, ensure good air circulation, and promptly remove affected leaves to prevent the spread of the fungus.
Root Rot: Root rot is a common problem for Calathea plants when their roots are constantly exposed to excessive moisture. This condition is usually caused by overwatering or poorly draining soil. To prevent root rot, make sure your Calathea is potted in well-draining soil and allow the top inch of the soil to dry out before watering again.
Bacterial Leaf Spot: Bacterial Leaf Spot, caused by various bacteria, can result in water-soaked lesions on the leaves. These lesions can eventually become necrotic and lead to leaf death. Avoid overhead watering and remove infected leaves to prevent the spread of bacteria.
Powdery Mildew: Powdery mildew is a fungal disease that can affect Calathea plants, resulting in a white, powdery coating on the leaves. This disease is favored by high humidity and poor air circulation. Reducing humidity and ensuring proper ventilation can help prevent powdery mildew.
To maintain healthy Calathea plants, it's essential to inspect them regularly for signs of pests and diseases. If any issues are identified, take appropriate action promptly, such as isolating affected plants, treating with insecticidal soap or neem oil for pests, and removing and disposing of severely infected plant parts for diseases. Additionally, maintaining optimal growing conditions, including adequate humidity and proper watering practices, can go a long way in preventing these issues.