Information on Pesticide Usage

Pesticides are often useful in the management of plant diseases when used properly. Pesticides are also frequently used when they shouldn’t be or for the wrong disease. The following is helpful to keep in mind when considering the use of a fungicide:

  • Submitting samples to a plant diagnostic clinic can help ensure that a product for control is going to be effective, and is applied appropriately for best control.
  • The correct fungicide applied at the right time is very important to achieve maximum control of the problem.
  • Many Pesticides work as a protectant on the plant surface, therefore the fungicide must be in place before the pathogen infects the plant for best results.
  • Often doing nothing is as effective as spraying the wrong chemical for the disease, applying at the wrong time, obtaining poor coverage, or applying an insufficient amount.
  • Although a chemical may be labeled for a particular disease it may not be labeled for the plant use or site use. Therefore it is extremely important to consult the label for exact use. Always read and follow label directions. Labels are federal law.

Four leaf spots are shown below, caused by four types of diseases. We recommend that NONE of these be controlled with Pesticides. Only the anthracnose on ash is caused by a fungus and fungicide applications are not generally recommended for control of this disease on established trees in Missouri.

Bacterial leaf spot and insect damage on hydrangeaBacterial leaf spot and insect damage on hydrangea
Eriophyid mite injury on Bradford pearEriophyid mite injury on Bradford pear
Impatiens Necrotic Spot Virus on impatiensImpatiens Necrotic Spot Virus on impatiens
Anthracnose on ashAnthracnose on ash