Phytotoxicity

Phytotoxicity refers to the damage caused by the misapplication of chemicals to plants.


Obviously, herbicides are supposed to be toxic to plants, but sometimes beneficial treatments can have a negative affect.

Photo of phytotoxicity by University of Maryland Extension

Signs of phytotoxicity

Plants affected by phytotoxicity may show any of these symptoms:

• Chlorosis (yellowing) of tips, margins or entire leaves
• Leaf spotting
• Stunted growth of parts or the entire plant
• Abnormal growth 
• Leaf curling, cupping or crinkling
• Defoliation (leaf loss)

What causes phytotoxicity?

Phytotoxicity can occur using old chemicals in new ways, new chemicals in the wrong way, or the right chemical on the wrong day. Some plant species are sensitive to certain chemicals, and some life stages are vulnerable to any type of treatment. Water stressed plants are more vulnerable to phytotoxicity. Phytotoxicity is frequently caused by the following:

• Applying horticultural oils on days that reach or exceed 90 degrees
• Chemicals that are carried on breezes to nearby plants
• Excessive fertilizer
• Herbicide residues that remain in the soil for months
• Spraying a plant with a treatment from the wrong distance

Even the most benign treatment can become phytotoxic if too much is used. This is why it is important to learn about individual plants and read labels thoroughly before products are applied. This is especially true for treatments that contain emulsifiers and solvents. Do your plants a favor and follow the directions.

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Plants affected by phytotoxicity will generally recover, but not always. Provide phytotoxic plants with a little TLC, an extra drink of water, and be sure to remove the cause whenever possible.

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