What Is Wrong With My Spirea?

Are the leaves curled and yellow?

Does your spirea have leaves rolled into tubes?

Does the whole plant look stunted, leaves have been discolored?

Are the leaves and branches covered with small bumps?

Have the leaves and twigs died back?

Are the leaves covered with white powder?

Are the leaves blotched?

Distorted, curled leaves are caused by aphids. These tiny insects can vary in color, green, pink, black, gray to completely white. They cluster under leaves and on growing tips where they feed on plant sap. Leaves, stems, and buds get distorted, and later leaves and flowers drop from the plant. You can control them by washing them off the plant with water spray. Insecticidal soap should be used with severe infestations.

Rolled leaves are caused by leafrollers. These green caterpillars with brown heads feed on the enclosed leaves and buds. If the infestation isn't severe, handpick the rolled leaves with caterpillars. Spray more heavily infested shrubs with light horticultural oil according to the directions of the label to smother the insects and any eggs.

If the whole plant looks stunted, and the roots have tiny galls on them the culprits are Root-knot nematodes. Prevent root-knot nematodes by applying chitin or introducing parasitic nematodes to the soil before planting. Solarizing the soil also helps in preventing root-knot nematodes. Adding lots of compost to the soil will encourage fungi that attack nematodes.

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.

Fire blight is a fungal disease that causes new shoots to wilt suddenly, turn dark and die back. The disease eventually spreads, killing the whole plant. Prune out diseased tissue, cutting back at least 6 inches below the discolored area. Destroy or dispose of prunings. Disinfect pruners after each cut in a 10 percent bleach solution. Spray copper or Bordeaux mix the following spring during flowering.

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. Any commercial fungicidal spray will protect your plant from further infections.

Your plants might be suffering from fungal leaf spots. 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. Prevent problems by thinning plants to provide good air circulation.

If the lower foliage is burned, the problem may be dog urine. Dog urine is mildly toxic to most ornamental plants, as well as lawns. It may discolor spirea foliage and even kill lower branches that dogs visit repeatedly. Spray vulnerable foliage with an anti-transpirant spray to provide some ground-level protection. Also try screening the plants or spraying foliage with a repellent spray.