To correctly diagnose the problem, a careful examination of the situation must be taken. Accurately identify the plant. Some insects and diseases are plant-specific, so this will help narrow the possibilities.
- Look for a pattern of abnormality. Compare the affected plant with those on site, especially of the same species. Differences in color or growth may present clues as to the source of the problem. Nonuniform damage patterns usually indicate insects or disease. Uniform damage over large areas usually indicates other factors, such as physical injury, poor drainage, or weather.
- Carefully examine the landscape. History of property and adjacent land may reveal any problems. The number of species affected may help distinguish between infectious pathogens that are more plant-specific as compared to chemical or environmental factors.
- Examine the roots. Brown or black roots may be a sign of problem. Brown roots may indicate dry soil or the presence of toxic chemicals. Black roots may be the result of overly wet soil or the presence of root-rotting organisms.
- Check the trunk and branches. Examine for wounds because they can provide entrances for pathogens and wood-rotting organisms.
- Note the position and appearance of affected leaves. Dead leaves at the top of a tree normally indicate environmental or mechanical root stress. Twisted or curled leaves may be the result of viral infection, insect feeding, or exposure to herbicides. The size and colour of the foliage may also tell a lot about the condition of the plant.
The treatment method will depend on the species involved, the extent of the problem, and a variety of other factors specific to the situation and local regulations. If you are unsure of the nature of the problem or the proper treatment, consult a professional.