Blight on Bushes

What is Blight?

• There are many different diseases that can attack a plant, so it is important to understand exactly what blight is to be able to identify it correctly. Blight disease can be caused by a bacteria, fungus or virus that will infect the canes, fruit, foliage or flowers of a plant. Indication that blight has infected your bush can be withering of stems, flowers and foliage, growth stoppage and death of parts of the bush, especially tender new growth.

Bacterial

• The two common bacterial blight diseases that infect woody bushes are Pseudomonas bacterial blight (bacterial canker) and Erwinia fire blight. Members of the Rosaceae plant family, such as apple, pear, rose and cotoneaster, are susceptible to fire blight. Bacterial canker disease can attack any number of bushes, but lilac bushes and members of the Prunus plant family, like flowering cherry, are particularly sensitive. Signs of bacterial blight are black spots, streaks or entire black areas on the leaves and flowers. Treatment with a copper-based spray in the spring will kill or stop the bacterial blight from spreading. All infected growth on the bush must be pruned off and destroyed. Pruners should be disinfected after pruning to avoid spreading the disease further. As temperatures increase and cool spring rains cease, bacterial blight generally dies out, though it can remain dormant in the soil and on bark until next season.

Fungal

• Many fungal diseases can attack bushes, but roses and blueberry bushes are most frequently plagued. Botrytis blight, sometimes called grey mold, is one of the most common fungus blights that flourishes after a cool, damp period, or in high humidity. It attacks all parts of the bush: buds, stems, leaves, roots and particularly young, tender new growth. Infected areas will appear water-soaked and brown, followed by a grayish fuzz appearing while the underside of the plant slowly rots. Good air circulation around your bushes and keeping water off the foliage are preventive measures, along with routinely spraying your bushes with fungicide. Once your bush has been infected with botrytis blight, or any fugal disease, the infected parts must be pruned off and discarded to save the remaining bush.

Viral

• Viral blights are less damaging and threatening to bushes than bacterial or fungal blights. Viral blights generally are restricted to a single bush or plant and do not spread to surrounding plants. It is more difficult to determine if your bush is infected with a viral blight because many times the virus appears similar to a nutrient deficiency. Unhealthy or stressed bushes are more susceptible to viral blights than healthy strong plants. Prune off infected areas and take a sample to the local university cooperative extension office to verify if your bush has a viral blight or is lacking a particular nutrient and the appropriate treatment.