A Barberry Shrub In My Garden Is Looking Sickly. Are There Any Pests And Diseases That Might Have Affected It?

Have the leaves and shoots of your barberry blackened and do the leaves have moist or brown sunken spots on them?

Are the leaves of your barberry shrub wrinkled and discolored?

Have the leaves been chewed and do the branch tips have webbing on them?

Have the leaves shriveled and turned brown?

Do the leaves have notched leaf margins?

Are the twigs of your barberry shrub covered in small reddish-brown bumps?

These symptoms often indicate a fungal disease - Antrachnose. This disease is causing problems mostly in cool and wet springs. In severe cases, twigs can die back and defoliation can occur. All diseased leaves and shoots should be pruned off, gathered and disposed of. Cut affected branches several inches below the damaged area. Early in the season, spray with lime-sulfur.

Wrinkled and discolored leaves on barberry usually indicate 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 become distorted and later 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 or neem oil should be used with severe infestations.

Webbing on branch tips and chewed leaves are most likely caused by Barberry webworms. These caterpillars are 1.5 inches long and black. They form a web nest in midsummer by tying leaves and twigs together. If the infestation isn't too serious, handpick the caterpillars and destroy them. Large infestations can be controlled by BTK spray. Spray the plants three times, with one week between every application.

The cause for shriveled and browned leaves is a fungal disease - Barberry wilt. This soilborne fungus attacks water-conducting tissue, causing leaves to wilt and eventually killing the entire plant. Remove the whole affected plant and its surrounding soil and replace it with fresh soil.

Leaves with notched leaf margins on barberry are most likely caused by insects - Japanese weevils. Adult Japanese weevils feed on foliage, but the larvae attack roots exclusively. 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.

Redish brown bumps on barberry twigs are caused by the Barberry scale. Severe infestations sometimes cause yellow foliage and stunted growth. They are most active in June and July. In early spring spray twigs with dormant oil. Superior oil or several applications of insecticidal soap helps in controlling them during the ongoing season.

If the whole plant looks stunted and generally lacks vigor the most likely cause is Nematodes. Nematodes are microscopic, wormlike creatures that attack the roots of the plants. A clear sign of the nematodes infestation are knotlike galls on the roots which can be seen if you dig up the plant. To prevent nematodes mulch regularly with compost to ensure that soil organic matter levels remain high. Heavily infested plants can only be removed and replaced with some other plant species.