My Perennial Aster Flowers Are Affected by Some Disease Or Pest. How Can I Found Out What Is Wrong With Them?

Are the leaves, stems, and buds on your aster distorted, sticky with clusters of small insects on them?

Do the leaves and flowers of your aster have holes on them?

Are the leaves of your aster covered with white powder?

Are the flowers of your aster deformed and yellowish with small tarlike spots on undersides?

Do the leaves have pale areas on upper surfaces and "downy" patches underneath?

Distorted leaves, stems and buds 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 latter leaves and flowers drop from the plant. You can control them by washing them off the plant with water spray. Introducing their natural predators will keep their number low. Insecticidal soap should be used only with severe infestations.

Holes in leaves and flowers in aster are caused by Japanese beetles. Adults of these insects devour leaves, stalks, and flowers of nearly 300 plant species. Their larvae feed on the roots of the plants. Handpick adult beetles into a can of soapy water but make sure to wear gloves as Japanese beetles are blister beetles. Apply parasitic nematodes to the soil to limit beetle grub populations. Use pyrethrin powder or neem oil as a last resort.

White, powdery patches on the leaves are caused by a fungus Powdery mildew. Powdery mildew usually appears in damp places. Encourage good air circulation around the affected plants by thining 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.

Deformed and yellowish flowers with small tarlike spots on undersides are caused by lace bugs. Remove debris in springtime and in fall to deter overwintering of these small insects. If the infestations are severe you can control them by spraying pyrethrin, insecticidal soap or superior oil on your asters.

Pale areas on upper surfaces of the leaves and "downy" patches underneath are caused by Downy mildew. This fungus spreads quickly during cool, wet nights and warm, humid days. Leaves will wilt and die. Remove and destroy all affected plant parts and encourage good air circulation around asters by thining surrounding plants. water asters early in the morning to make

Environmental issues might have caused your asters sickly look. These daisylike flowers love lots of water, so keep them well watered and the soil evenly moist. They do best in a sunny location. Divide them in spring every 2-3 years to prevent overcrowding.