City Of Greeley

Pesticides & Fertilization

It is always our suggestion to avoid using pesticides whenever possible, however, if you are having problems with either insect or weed pests in your landscape, pesticides may be the only way to control the problem. Mother Nature has a unique way of combating pest issues all on her own. Sometimes when pesticides are used, you will also be destroying beneficial insects as well.

Fertilization, if not provided for correctly, can seriously injure or destroy your vegetation. Fertilization should begin during the spring season close to leaf out and should slow towards August. Avoid feeding a plant when it should be getting ready for dormancy!

Pest Control

1. Trees, like other plants, are subject to insect infestations, which may endanger their well-being. If insects are at damaging levels, properly-timed spraying or soil injected pesticides are needed to control these infestations.

2. The decision to use pesticides should be made only after careful consideration. In many cases, undesirable insects are already being controlled by natural enemies or weather conditions and/or the health of the tree is not being affected.

3. Some situations may require pest control but before this is done, have a proper diagnosis of the problem. Know the pest name, plant name and the product recommended for best control. Blanket spraying of entire yards is a poor practice. Also, non-chemical methods of control should be considered first.

4. A pesticide used for insects in trees and shrubs must be labeled for the target pest and/or the tree it’s on. Read the label completely before using any pesticide.

5. Use only competent pesticide application companies licensed by the Colorado Department of Agriculture. They have the equipment to insure an adequate dosage, application and coverage.


1. Trees do not, as a rule, require fertilizer. In most cases adequate nutrients are available from the existing soil and lawn fertilization that regularly occurs.

2. If there is a nutrient deficiency and supplemental fertilization is recommended, the ideal time to fertilize trees is after they leaf out in the spring.

3. A common nutrient problem in Colorado is the availability of iron, manganese and other micro-nutrients to trees because of high pH soils, (pH is an index of acidity-alkalinity). A lack of micro-nutrients can cause a yellowing or chlorosis of the leaves, especially in some Oaks, Silver Maples, and Cottonwoods.

4. Always consult with a professional arborist or Colorado State University Cooperative Extension office to get an accurate diagnosis of the problem.