Tips on how to use this section
The symptoms of the most common problems are in the left column of the chart. In the right column are the probably causes of those symptoms. For those problems for which there is detailed information in a different part of Yardener’s Helper, the name of the problem is linked to a detailed file. For those problems for which there are no additional files, the discussion is found in the paragraphs below the chart.
|Solving Barberry Problems|
|Plant Dies During Summer||Moisture Stress|
|Foliage Curls; Turns Yellow||Aphids|
|Leaves Discolored; Covered with Small Bumps||Scale|
|Webbing Binds Leaves and Twigs Together||Webworms|
|Holes in Leaves||Weevils|
|Sunken Spots on Leaves||Anthracnose|
|Leaves Turn Brown or Reddish; Fall Prematurely||Wilt|
Plant Dies During Summer Due To Moisture Stress.
Entire mature shrubs, or sections of some shrubs may die very suddenly in the summer. This results from damage to the roots from severely fluctuating moisture (repeated drying out and getting waterlogged). Spread 2 to 4 inches of organic mulch on the soil over the roots to avoid this problem. Be sure and plant barberries in soil that has sufficient organic matter in it that it drains well, yet retains moisture.
Webbing Binding Leaves and Twigs Signals Webworms
Barberry webworm caterpillars are blackish with white spots, and are nearly 1-1/2 inches long when full grown. They bind together leaves and twigs, forming nests within which they feed. This webbing usually starts after midsummer, and the nests remain on the bushes during the winter. The webworm is prevalent in the southwestern United States. It attacks both common and Japanese barberry. Handpick or prune out as many nests as possible. To effectively control large infestations, spray foliage with a product containing Bt (Bacillus thuringeinsis) as soon as small worms are visible. Follow label instructions for use and storage carefully. For more information see the file on Controlling Caterpillars
Holes In Leaves Are Due to Weevils.
Weevils sometimes chew the edges of Japanese barberry leaves, devouring the whole leaf except for its midrib and veins. They are about 1/4 inch long, varying from light to dark brown, with fine, parallel impressed lines on their wing covers. They are sometimes called snout beetles because their heads are elongated into long, slender downward-curved snouts, terminating in their mouthparts. Weevils commonly live under tree bark or in other plant tissues. Their grubs (larvae) often attack roots, which may endanger the life of the shrub. Coat barberry stems with Tanglefoot ä to prevent the adult weevils from climbing up and eating the leaves. Introduce predatory nematodes into the soil according to label instructions around the Japanese barberry to attack the grubs feeding on the roots. For more information see the file on Controlling Weevils
Sunken Spots on Leaves Indicate Anthracnose.
This fungal disease forms distinct lesions on barberry leaves, which appear as moist, sunken spots with fruiting bodies in the center. Leaf spots may run together, resembling a blotch or blight. The dead areas follow the veins or are bounded by larger veins. Sometimes terminal shoots on the barberry die back to several inches below the buds. Pustules containing pinkish spores appear. A severe attack causes dieback and defoliation. Gather and destroy fallen leaves. Prune away diseased branches. Maintain shrub vigor by feeding and watering well, especially during droughts. To prevent the spread of the disease, spray unaffected foliage with a general garden fungicide listed on the label as effective against anthracnose. Use as directed. For more information see file on Dealing with Fungal Disease.
Leaves Turn Brown or Reddish and Fall Prematurely from Wilt
A soil-dwelling fungus sometimes infects the water-conducting tissues of barberries, causing a wilt disease. The leaves become brown or reddish, shrivel and finally fall. Entire plants may eventually die. Remove and discard infected plants and the soil immediately surrounding them. Disinfect tools by dipping them in a solution of hot water and household bleach. Replant the area with some other shrub that is labeled resistant to wilt.
Foliage Burned by Dog Urine.
Since barberries are often planted along walks and at corners of the property they tend to be visited by passing male dogs. Dog urine can discolor Japanese barberry foliage and even kill low branches. Coating foliage with an anti-transpirant spray gives it some protection. Screen vulnerable shrubs with a low fence or spray them with a repellent spray listed on the label for use with pets. Use as directed. For more information see the file Dealing With Dogs and Cats.