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.

The Penn State University Landscape Pest Problem Solver is a great site with many links to Penn State Fact Sheets and publications as well as USDA Forest Service Pest Alert Fact Sheets

Penn State University Plant Disease Fact Sheets

Penn State University Entomology Fact Sheets

Penn State University Woody Ornamental Insect, Mite and Disease Managment Guide

DCNR Forest Pest Fact Sheets

USDA Forest Service Pest Alert Sheets

USDA Forest Service Tree & Forest Health Publications

USDA Forest Service Forest Insect and Disease Leaflets

Penn State Publication Perserving Trees duing Development

Penn State Intergrated Pest Management Website

Penn State University Pesticide Education Website