Sick Plant Symptoms

This time of year, a lot of plants look a little sick. Deciduous trees have lost their leaves, and look barren, or maybe even dead. Evergreen broadleaf trees still have their leaves, but most look pretty battle scarred. Leaves exhibit spots, necrotic tissue, or even missing sections. Some of this is residual from the previous season, and may be less apparent with spring growth. Often these symptoms are unsightly, but do not pose a risk for the plant; they simply indicate current or past environmental conditions. Sometimes the symptoms do indicate a more serious problem that should be treated, or the plant removed.

When you start diagnosing a sick looking plant, take some time to check it and its surrounding site for symptoms and clues:

• Look at the leaves for spots, mold, sun burn, yellowing, and necrotic patterns. But don’t just look at individual leaves; look for patterns in the plant or tree canopy. Is one leaf having the problem, a group of leaves, or all the leaves?
• Do some branches look dead? If so, is it just one branch, a scattering of branches, or a whole section of the canopy?
• Is the bark intact? Are there cankers high on the trunk, or low near the soil line? Does the trunk flare and visible root structure look healthy?
• Did the symptoms occur all of a sudden, or did they occur gradually over a period of time? Are they related to seasons?
• What is happening in the area around the plant? Are nearby plants experiencing the same thing? If so, are they plants of the same species, or of different species?
• What site events have occurred in the last several years – construction, landscaping, broken irrigation system, fertilization mishap, flooding, extreme weather (freezing or drought)? Symptoms for some problems manifest several seasons or years later.

Flagging (dead branches) may indicate blockage in the vascular system.	Black Spot of Rose is very common in roses, especially late in the season.
Cankers low on the trunk may indicate environmental damage, or below-ground diseases.	Conks feed on dead wood, indicating this tree is dying, and may become a hazard.

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Try to identify the plant by its scientific name. Many plant diseases are very specific to a particular species, so knowing the plant name can help you research the specific disease. It is also useful to be familiar with some of the diseases common in the San Francisco Bay Area; for example: powdery mildew, downy mildew, rust, anthracnose, black spot of rose, peach leaf curl, wilt, water molds, and sudden oak death are very common in the area. Armed with your site research, scientific plant name, and basic awareness of symptoms in your area, you may be able to identify the plant disease or environmental condition that produced the symptoms you are seeing.