What Is Wrong With My Forsythia?

Are the upper surfaces of lower leaves stippled with small yellow or red dots; leaves, stalks, and stems may be distorted or webbed?

Are the leaves yellow, branches, and leaves are covered with small bumps?

Have the edges of the leaves been eaten, some leaves may have been skeletonized?

Does the whole plant looks stunted, leaves are yellow and spotted, roots have tiny galls?

Does the trunk or stems have tumor-like swellings?

Are the flowers and twigs shriveled?

Does the leaves have sunken or brown spots?

Have the roots and base of the stems been gnawed?

If your plant shows these symptoms, check for mites on the lowest leaves of forsythias. You can control 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.

Yellow 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.

Weevils feed on the edges of forsythia leaves during the day. They sometimes devour the whole leaf except for the midribs and large veins. The application of a sticky substance on the lower stems should prevent adults from climbing up the plants. Introduce parasitic nematodes into the soil to control the larvae. Spray leaves several times with pyrethrin for severe infestations of adults.

If the whole plant looks stunted, the leaves are yellow and spotted 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.

Phomopsis gall is a fungal disease that causes these symptoms. To prevent this disease, do not plant any forsythia shrub that has suspicious visible galls on the stems. Destroy any heavily infected plants. If only a few galls are present, cut off and destroy the affected stems. Sterilize pruning tools afterward in a solution of household bleach and hot water to avoid spreading the disease.

Twig blight is a disease that is known to cause problems for forsythia shrubs. Prune off affected parts back to live wood. Spray plants with copper fungicide or lime sulfur fungicide when symptoms first appear and then every 10 days in wet seasons. Avoid overhead watering.

Leaf spot diseases like Anthracnose caused by various fungi sometimes attack forsythia. 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 to provide good air circulation.

Small rodents sometimes nest in winter mulch near forsythia stems and gnaw at plant tissues. Do not pile mulch against stems. Wait until the ground freezes before spreading winter mulch so that mice, voles, and other rodents are forced to find other nesting areas.

If the tips of forsythia's arching branches that touch the soil take root, that is a normal thing for forsythia. Either prune branch tips to prevent this or clip off the rooted sections from the branches and encourage them to develop as new shrubs that can be transplanted elsewhere.