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Using Chemicals Correctly

Dundee Fact Sheets

Using Chemicals Correctly                  

Print This SheetChemicals

When you discover an ailing plant in your yard or garden, study it carefully. Look for insects or symptoms of disease. Bring a sample of the problem to the Garden Center to have our professional staff advise you. Sometimes the problem is caused by cultural difficulties and cannot be cured by chemicals. Sometimes the best course of action is to do nothing! Guessing when you buy a pesticide, using whatever is in the garage, or using one needlessly can be costly, time-wasting, and/or possibly dangerous.

Always read the label entirely before buying and using a chemical. The labels have a great deal of useful information, especially about precautions and rates of application. Look for warnings about varieties of plants the product should not be used on. Use the chemical only for its intended purpose and only as directed. Look for information about what temperatures it’s okay to use the chemical in. Some chemicals will harm plants if it’s too hot or too cold. DO NOT apply the chemical at a stronger rate than recommended. Not only can that be dangerous, but it may also make the product ineffective. For example, if a weed killer is mixed too strongly, it may just burn off the tops of the weeds, not killing the roots, and the weeds will reappear in a few weeks.

Here are some terms that will help you understand what type of chemical you need:

INSECTICIDE...Controls insects and spiders. Not all insecticides control all

MITICIDE...Controls mites such as red spider mites.

FUNGICIDE...Controls fungus diseases. Has no effect on insects. In general, fungicides are good at preventing disease, but not as good at fixing an existing problem.

HERBICIDE...Controls weeds but may also damage desirable plants. Some weed killers are selective (kill only certain types of weeds); others are non-selective (will kill all plants).

RODENTICIDE...Controls rodents such as mice.

REPELLENT...Keeps pests away, but won’t kill them.

PRE-EMERGENT WEED KILLER...Use before weeds sprout. Keeps annual weeds such as crabgrass from growing. Has no effect on plants once they have germinated. Has no effect on perennial weeds such as dandelions.

CONTACT KILLER...Kills by coming into direct contact with the pest.

SYSTEMIC KILLER...Makes the plant poisonous to the insect feeding on it.

Measure chemicals accurately when mixing. Some common measurements include:

16 oz. = 1 lb.
1 fluid oz. - 2 tablespoons
16 fluid oz. = 1 pint
2 pints = 1 quart
8 pints = 4 quarts = 1 gallon
3 teaspoons = 1 tablespoon
1 cup = 16 tablespoons
2 cups = 1 pint


Don’t forget that there are many fine organic measures to consider.


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