How to Identify Brown Spots or Bumps on Leaves
- 1). Inspect the entire plant or tree. Looking closely at the type of brown spots can help you figure out the plant's condition, and can also help you decide what to do.
For instance, little brown spots on the leaves of trees that tend to get spots around the same time every year--typically late summer--indicate fungal infestation. Depending on the fungus, and the plant, they can be flattened areas of necrotic tissue, or little raised scab-like bumps. In some cases there won't be any tissue at all --just holes.
In other cases, the spots may be found only on one side of the tree or plant, indicating that perhaps that side is exposed to something the other is not. This can be true for street trees, and plants that grow near busy, high traffic areas. - 2). Inspect the spots. Different causes can lead to different kinds of spots. If leaves have seasonal necrosis, or circular spots of dead tissue, it's likely to be a fungus. Sometimes the tissue can be raised and scab-like, or will drop out altogether, leaving a hole.
In other situations, the damage may turn the leaves slimy or mushy, and the plant will have a specific odor. This is likely to be bacterial leaf spot, which is similar to fungal leaf spot, but invades through areas of damage on the leaves.
Sometimes spots are caused by sunburn, which typically affects the leaves that are most exposed. Sunburn typically starts at the leaf edges, curling them inward. - 3). Inspect the surroundings. The environment and atmosphere surrounding the plant can provide abundant evidence about the origin of any spots. If there is poor air circulation or sun penetration, high humidity, dew, fog, or rain, the spots probably indicate fungus or bacteria, which thrive under those conditions. Conversely, heat and dryness are likely to indicate spots caused by sun damage.
The location of the plants--near busy streets, sources of air pollution, or certain industries--may be a factor in chemical damage. Such damage could come from acid rain, road building activity, or nearby herbicide use.
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