Bacterial, Fungal, and Viral Infections in Trees and Shrubs

Infectious, disease-causing pathogens that may be particularly harmful to plants during wet seasons. With proper pruning, care and treatments we can help your plants defend themselves and recover from these infections.

What are Bacterial, Fungal, and Viral Infections in Trees and Shrubs?

In addition to being attacked by insects, trees and shrubs can be infected by a wide range of pathogens. These typically fall within three categories – bacterial,viral and fungal.

Bacterial

Bacteria are microscopic, single celled organisms that can reproduce rapidly in ideal weather and host conditions. Bacteria enter and infect a plant by an opening in tissue. Wounds, pruning cuts, environmental stress and damage can provide entry points for pathogens. Infection can be spread throughout the plant once inside the plant tissues. Bacterial diseases are generally categorized as vascular wilt, necrosis, soft rot, and tumors. Bacterial diseases often thrive in wet conditions.  

Some examples of bacterial tree diseases are fire blight, bacterial spots, and cankers. In Vermont, bacterial infections are especially common in fruit trees. 

Fungal

Fungi use plants as a food source. Most fungi reproduce through spores and they have a few different ways of infecting a host plant.  Some penetrate plant tissue, while others require openings in the plant, such as stomata in leaves, lenticels in fruit, flowers, or wounds.

Fungi can overwinter in host plants and also remain present on dried leaves, limbs and other debris on the ground. Some can lie dormant in soil for years until ideal conditions arise. Fungal spores will spread in rain and wind, infecting the plant tissues. Some examples of fungal tree diseases include apple scab, tar spot, powdery mildew, cedar apple rust, and black knot. 

Viral

Viruses are submicroscopic parasitic particles that enter living cells. The plant host cells do not recognize the virus as an invader and will use valuable energy to help the viruses replicate. Viral infections can spread in a number of ways. The most common vectors are through other organisms (such as insects). Viral infections can also be spread in plant pollen, seeds from infected flowering plants, through vegetative plant propagation and pruning, through natural root grafting, and by nematodes. Examples of viral plant infections include mosaic virus, apple chlorotic leaf spot virus, apple stem pitting virus, ringspot virus, and cherry leaf roll virus.

How can an infection be treated?

Proper routine and reactive pruning in addition to fertilization may be necessary to keep your trees healthy and also prevent spread of a bacterial, fungal or viral infection. In some cases, a pesticide treatment may be necessary to get the infection under control. Contact us to set up a consultation. We can help you by assessing the overall current health of your tree(s), making a diagnosis, and determining your management options. We’re here to help you make the best choice for your trees!