Diagnosing plant problems can be a difficult task. To diagnose plant problems, you need to know how a healthy plant grows and have some knowledge of the stresses that affect plant health. You need an understanding of the plant’s normal appearance before you can begin to monitor for signs and symptoms of a problem.
Plant problems can be grouped into four major categories:
Cultural – problems that arise from the care of the landscape, such as fertilizing, use of herbicides and pesticides, improper pruning, inadequate or over watering, improper planting, over mulching, etc
Environmental – problems often out of our control, caused by nature, such as droughts, hail, lightning, high or low temperatures, floods, etc
Diseases – plant problems that are brought about by infectious agents such as bacteria, fungi, nematodes and viruses. Common diseases include leaf spots, vascular wilts, cankers, and root rots
Insects – plant problems caused when insects chew leaves, suck sap (plant food) from leaves and twigs, or borer into the stems. The vast majority of insects in our landscapes are not harmful to our plants and some are beneficial because they prey on harmful insects
When we first see a plant problem (e.g. chewed or distorted leaf), often our first impulse is to apply a pesticide without even knowing what caused the injury. We are usually wasting time and money, and sometimes causing more harm than actually solving the problem. Proper diagnosis of the problem is critical and takes knowledge of the plant and the pest. Often you might need some help from a landscape professional or have to bring a plant sample into your local Penn State Cooperative Extension Office.
The following websites will help you gain knowledge about diagnosing plant problems in your landscape.