What Is Wrong With My Mahonia?

Are the stems, leaves, buds, flowers, or fruit covered with gray mold, leaves may be blotched or discolored?

Are the leaves pale on their upper side and are there any dusty blisters on the undersides?

Are the leaves spotted or blotched?

Are there large or small holes in leaves, leaves may have been skeletonized?

Are the leaves covered in coarse stippling and may appear silvery?

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

Are the leaves covered with small bumps?

Gray mold on stems, leaves, buds, flowers, or fruit is probably caused by fungal disease - Botrytis blight. You can prevent Botrytis blight disease by planting in areas with good air circulation. Water plants sparsely. Severely infected plants should be removed. Spray weekly with a copper fungicide until the disease is under control.

Likely cause for these symptoms is a fungal disease - Rust. Provide good air circulation around plants by thining them. Avoid making leaves wet when watering. All infected leaves should be removed. Spray leaves with sulfur early in the season to prevent rust or to treat mild infections.

Your plants might be suffering from fungal leaf spots. Spots may enlarge rapidly, especially in wet weather. Prune off all infected leaves. Spray plants with sulfur to prevent the disease from spreading, especially if the weather is wet. Prevent problems by thinning plants to provide good air circulation.

Barberry looper is a white-striped, dark gray caterpillar of a small, grayish-brown moth. Looper populations are usually held in check by natural enemies, but if they do become problematic larvae can be hand-picked from the plants. The application of BTK (Bacillus thurengiensis) will effectively kill younger larvae.

These symptoms may indicate thrips. Thrips are tiny, yellow to black flying insects. Severely infected plant parts should be removed and destroyed. Control thrips by introducing lady beetles or lacewings, their natural predators. Insecticidal soap helps in severe infestations.

White, cottony clusters on leaves and stems are caused by mealybugs. These tiny insects are covered with a fluffy white coating. 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.

Drought and too much water both curl and brown mahonia foliage. Without an adjustment to the watering schedule, the shrubs may drop their leaves. Leaf scorch threatens mahonias in too much sun or wind, blemishing the leaves with the greatest exposure with irregular yellow or brown areas. The scorched foliage may wither and drop.