Why Does My Croton Plant Look Unhealthy?

Do the stems have swollen, tumor-like growths on them?

Do the leaves have spots or blotches?

Are the leaves covered with white powder?

Are the leaves stippled with yellow and the foliage is webbed?

Do the leaves and stems have white, cottony clusters on them?

Are the leaves covered with small bumps?

Did the leaves become distorted due to excess moisture in the soil?

Bacterial disease Crown gall causes wartlike swellings on stems of Mandevilla. Gall bacteria are introduced into plants that are vulnerable due to wounds. If the plant is only slightly infected, prune off diseased growth. Destroy severely infected plants and avoid replanting Mandevilla or any susceptible plant species in the same spot.

Your plants are suffering from fungal leaf spot. These can come from several fungus diseases, causing spots to occur on foliage. Spots may enlarge rapidly, especially in wet weather. Destroy infected leaves or plants. Spray plants with sulfur to prevent the disease from spreading, especially if the weather is wet. Spray between rains. Prevent problems by thinning plants to provide good air circulation.

White, powdery patches on the leaves are caused by a fungal disease Powdery mildew. Powdery mildew usually appears in damp places. Encourage good air circulation around the affected plants by thining them and any surrounding plants. Water plants from bellow to keep foliage dry. Any affected leaves should be cut off and removed. The appropriate fungicidal spray will protect your plant from further infections.

Leaves stippled with yellow and webbed foliage is caused by spider mites. These tiny, spider-like pests feed by sucking sap from the underside of the plants leaves causing yellow flecking on the upper leaf surfaces. You can control spider mites by spraying plants thoroughly with water 2-3 times a day for several days. For severe infestations, spray plants with insecticidal soap, or pyrethrin as a last resort.

White, cottony clusters on leaves and stems are caused by mealybugs. These tiny insects are covered with a fluffy white coating. They feed by sucking plants sap. They produce sticky substance honeydew which makes leaves sticky. You can control them by washing them off the plant with water spray. Insecticidal soap should be used with severe infestations.

Leaves covered by small bumps are caused by scales. These tiny, shelled insects often feed on the undersides of the leaves, causing an unhealthy appearance with yellowish blotches on the upper leaf surfaces. Scrape off minor infestations with your fingernail. Prune out badly infested growth, or use a soft brush and soapy water to gently scrub the scales off the stems. Control scales by spraying insecticidal oil during the growing season.

If a plant has absorbed more water than it needs, it can cause the plant’s cells to expand and stress. Often, these cells are filled to the point of rupturing. Burst cell damage is called edema. You can check for signs of edema by noticing any blisters or lesions on the plant. Eventually, these lesions will turn to dark or even white scar tissue. Another sign of edema is indentations on the top of leaves.

Croton caterpillars, Achaea janata, eat the leaves of crotons, leaving behind only the stems and veins of the leaf. Regular applications of neem oil have been effective at reducing leaf consumption, but if the caterpillars persist, Bt (Bacillus thuringiensis) can be sprayed onto the plants as well.