What’s Killing Your Landscape Plants?

Posted: August 4, 2012

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...

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.  

For some online help diagnosing tree and shrub disorders, visit  and click on Caring for Trees. 

Vincent Cotrone, Urban Forester with Penn State Cooperative Extension