Caragana arborescens is a deciduous shrub or small tree native to Siberia. It has bright-green foliage and a columnar or rounded form and reaches heights up to 20 feet. Several different diseases infect caragana shrubs.
A variety of different fungi cause leaf spot infections in caragana shrubs. Fungi and bacteria both cause branch cankers, while different fungal infections result in stem decay.
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Caragana shrubs that are infected with leaf spot develop circular spots with dark edges on the foliage. Shrubs may lose their leaves during wet weather. Branch cankers are sunken areas of diseased bark that form on caragana branches. Infected branches lose their leaves. Severe infections result in branch dieback or shrub death. Stem decay fungi break down the cell walls inside the wood, causing wood rot. Mushrooms or bracket-like growths called conks from on the outside of the plant.
Chemical controls are rarely necessary for leaf spot. The University of Minnesota Extension website recommends watering shrubs less often if leaf spot appears, and then only watering the plants near the base. You can control branch cankers by pruning out the canker as well as the surrounding plant material. Be sure to disinfect your tools between cuts to prevent spreading the fungus to other plants. Watering and fertilizing shrubs to keep them in good vigor helps to prevent stem decay.