North America is rich in native shrub species. From flowering to fruiting and evergreen to herbaceous, these natives include boxwoods, roses, blueberries, raspberries and forsythias there is a shrub to fit your landscape needs. While these bushes range in growth rates, colors and overall appearance, their susceptibility to fungal diseases is quite similar.
Fungus on your bushes is a sign of infection. The infection can be caused by a variety of fungal diseases. The most common shrub diseases include powdery mildew, stem blight, anthracnose and verticillium wilt. While many fungal diseases cause cosmetic damages to bushes that can eventually be corrected, fungal diseases such as verticillium wilt can be fatal to many shrubs.
Fungal diseases are caused by the development of fungal spores. These detrimental spores lie dormant during the winter months and multiply during the spring and summer. The fungal spores are commonly found in bushes that are already infected with fungal disease, as well as in decomposing debris that lies around your bushes. Fungal spores are most active during the cool, wet seasons of spring where they are swept into the bush by wind and rain.
When the windy, rainy season comes to an end, fungal spores that have settled onto the surfaces of a bush begin the course of infection. Bushes that have been infected will display symptoms that include foliage wilting, drooping, discoloration, fungal spots, decay, dieback and growth stunt. While some symptoms may appear rapidly, other symptoms appear gradually, and even over the course of several seasons.
Careful and timely pruning is an effective method of controlling and preventing fungal infections in bushes. Bushes are naturally densely foliated. This heavy foliage reduces penetration of light and air to the shrub's interior. This reduced flow slows the bush's reproduction and increases the growth rate of infectious fungal spores. Thinning interior branches increases the light penetration and air circulation throughout the interior, which reduces the bush's susceptibility to fungal diseases. Fallen leaves and other debris should be removed from around infected shubs and destroyed as spores overwinter in debris and can reinfect the plant, according to the University of Connecticut's Integrated Pest Management Program.
Verticillium wilt is a fungal disease fatal to hundreds of bush and tree species. This soil-borne disease infects the bush through its root system, according to University of Minnesota Extension. Once it enters the root system, it attacks the bush's vascular system and gradually restricts the system from providing nutrients and water to the rest of the bush. Symptoms of verticillium wilt are quite similar to other fungal infections and often result in the misdiagnosis of the bush. Verticillium wilt infections can be confirmed by inspecting a cross section of the trunk. The heartwood of the trunk will appear discolored and outlined with red streaks.
There is no chemical treatment available for verticillium wilt. However, fungicidal treatments can be used to effectively control and prevent many fungal infections. Timely application is essential. Most chemical treatments are ineffective on severe fungal infections. It is important to treat infections early.