The term “canker” refers to a lesion on a twig, branch or stem, usually caused by a bacterial or fungal pathogen. The appearance of cankers varies, depending on the host and the pathogen. Often, the bark of the affected stem or trunk is sunken and discolored. Fluids may ooze from a canker or fungal fruiting structures may appear on the bark covering or surrounding the lesion. In some cases, lesions remain small and isolated, causing no major problems for the host plant. In other cases, the canker spreads widely, causing death of twigs, branches or even the main trunks of trees. The best known example of the destructive potential of a canker disease is chestnut blight, caused by the fungus Endothia parasitica, which caused the virtual extinction of the American chestnut within 40 years of its accidental introduction to the United States in about 1900.

If you have paid attention to the news media over the past few years, you probably know honey bees are having problems. One of the most widely publicized is a phenomenon known as colony collapse disorder, or CCD. This problem, which causes entire colonies of bees to die suddenly and mysteriously, was first recognized in the U.S. in 2006. But CCD is just one of a series of new problems to affect U.S. honey bees over the last 30 years.

As an arborist, I work with a lot of people who care deeply about their trees and shrubs. Almost once a week, I will get a call from someone who is alarmed that something new they’ve noticed on their tree might be a major problem. Sometimes it is a problem that needs help, but often it is something that looks bad, but isn’t. Here are some of the common issues that arise.

Rose gardeners throughout the country need to be vigilant in watching for the symptoms of an increasingly common problem known as rose rosette disease.

They don’t have their photos hanging on the post office walls, but these garden pests are notorious. Here are the ‘Most Wanted’ of the Midwest garden, their rap sheets and how to bring them to justice ...

What’s that spot on the leaves? Or that fuzzy stuff? Why are the leaves falling off? Here’s how to tell whether your woody plants are really sick or just have a little case of fungus.

Galls are the enlargement of plant tissue caused by injury or irritation by parasitic organisms such as insects, mites, nematodes, fungi and bacteria. They are also interesting looking — knotty, lumpy and sometimes colorful. Learn which ones are common in your garden.