Fertilizers and Pesticides

Many chemicals are used in lawns and gardens by homeowners. These are mainly fertilizers and pesticides (herbicides, insecticides and fungicides). These chemicals are very effective when used in the proper place, using the labeled directions. Modern agriculture could not feed us without them.

Before using any chemical it is important to ask yourself some questions: Do I have a clear indication that this product is needed? Is it the proper time to use it? Do I have the equipment and skills for proper application?

To prevent problems, one must always read and follow the labeled directions. This label is a legally binding document between the seller and the user. Avoid the "more is better" approach with these products. This is true with all of them, but especially true with fertilizers which are often applied in excessive amounts in hopes of coaxing a better performance from plants. This is counterproductive and ends up causing toxicity to plants and polluting the environment.


All plants need 17 mineral elements for normal growth. Of these, three are most in demand by plants and may need replacement. These three—nitrogen, phosphorus and potassium (N-P-K)—are what is found in most commercial brands of fertilizers. Fertilizers are classified as either organic, produced by nature, or inorganic, manufactured commercially. Both types supply the exact same nutrients; the plants cannot tell the difference. There are advantages and disadvantages to both.


Herbicides are chemicals used to kill undesirable plants. There are many types, but there are three main categories based on the mode of action.

          Preemergent Herbicides: These are chemicals applied to the soil to prevent new weed growth. They must be in place before weeds germinate, although some will kill weeds immediately after germination. Generally they are applied in spring to prevent summer weeds such as crabgrass and fall to prevent winter weeds such as henbit.

          Postemergent Herbicides: Most of these herbicides are used for killing broadleaved weeds. Some are specific for other weeds such as grasses and sedges. Generally these chemicals are most effective on weeds which are growing rapidly in spring and fall. They tend to be much less effective on weeds which have reached maturity and are forming flowers and seeds.


          Non-Selective Herbicides: Of these herbicides, glyphosate, the chemical found in Roundup and many others, is far and away used the most. In fact, it is the most commonly used herbicide in the world. Glyphosate is a systemic herbicide capable of killing most plants which are green and which have an active metabolism. Glyphosate has a very low toxicity and is inactivated as soon as it comes in contact with soil.

Insecticides:  These are pesticides which kill insects and spiders. There are hundreds of different insecticides with an even larger number of commercial brands of these chemicals. They are constantly undergoing an evolution with pressure to restrict usage of the more toxic ones.

Insecticides are classified by their mode of action—systemic or contact—or how they are produced—natural, inorganic or organic. Current trends emphasize the use of  organic insecticides which have less undesirable effects on the environment and beneficial insects. Insect growth regulators are also being used more commonly. They are insect specific pesticides and have low toxicity to mammals.

There is a huge decline in honey bee population which has many contributing factors, insecticides being one of them. Always select an insecticide with low impact on good insects such as honey bees and only use them early in the morning or late in the evening when bees are not present.


There are a number of fungicides available. These chemicals are like antibiotics, they have a specific fungi which are sensitive to them, while others are resistant. This is an important fact when selecting one. Many of the effective fungicides are only available to commercial applicators and they all tend to be expensive.

When considering a fungicide, one of the most important facts to be aware of, is that no fungicide will ever make an existing fungal infection clear up. The only thing one can ever hope to achieve, is to prevent spread of new infections. Sanitation, removing infected plant material from the garden, is always important and is an effective companion strategy.

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