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Chicago Urban Gardening

The day to day experiences of a University of Illinois Extension Urban Horticulture Educator in Chicago, Illinois

Pesticides in the Garden

Posted by Ron Wolford -

Hand-in-hand with the gardening season come attacks by pests, said a University of Illinois Extension horticulture educator.

"The question often becomes 'to spray or not to spray,'" said Martha Smith. "You should ask yourself that question before grabbing a bottle of pesticide. Should you spray or is there an alternative?

"Most pest problems start out small. Perhaps an infested branch can be removed. Or, you could simply handpick the critters off a plant. This can save time, energy, money, and chemicals."

But unless you monitor your garden, you might not see the pest until it has consumed a major portion of your investment. At this time, chemical control may be the only choice, she added.

"Pests are sure to attack. Monitoring and considering control options are the signs of a responsible gardener," she said. "Remember, a pesticide is any product that is used to control a pest and a pest is anything harming your plant. A fungus, insect, bacteria, and rabbit could all be considered pests."

If the chemical option is selected, Smith recommended some tips to follow.

First, read the label. Understand what the product is intended to do and the timing of application. When during the lifespan of the pest is it best to apply? Correct timing will give the best control with the least amount of chemical.

"Correctly identify the pest," she said. "Caterpillars resemble sawfly larvae but the products to control them are different. Also, is that caterpillar a true pest? If you choose caterpillar control, don't question the absence of butterflies later in the season.

"Caterpillars can be voracious eaters but the majority will turn into colorful butterflies. Consider the 'pest factor' before spraying."

Mix material as directed. Don't think that if one teaspoon is recommended, two teaspoons will be better. Effectiveness will not be increased by doubling the amount of chemical. In fact, higher concentrations can harm plants.

"Follow all personal safety instructions on the label," she noted. "A sleeveless tank top and flip-flop sandals are probably not the recommended protective clothing. Consider long-sleeved shirt, pants, eye protection, socks, closed toe shoes and gloves if not already instructed on the label."

Use measuring utensils--don't guess at amounts. Have a set of measuring utensils specifically designed for chemicals. Write on them "chemicals only." Don't use utensils that are also used in food production.

"Spray on target," she said. "Don't apply a chemical across a 20-foot border when only two to three square feet require attention--it may not be necessary. Read the label to find out if the entire plant needs to be sprayed. Spray to the point of runoff and stop."

Application equipment should be in good working order. Leaks can lead to damage on non-target plants. Use equipment that is recommended on the label.

"Spray when the weather is calm," Smith said. "Pesticide drift occurs when spray is carried off target by the wind. Drift can also be minimized by spraying at a lower pressure and using the largest nozzle opening that will still allow you to complete the task.

"Watch the weather and avoid the heat of the day. Some pesticides will burn plant material if applied when temperatures are too hot. High temperatures can also cause some pesticides to evaporate and decompose quickly. Spray in the morning."

Spraying before rain or overhead irrigation should also be avoided. Spraying under these conditions not only reduces the effectiveness of the chemical by washing it off the plant, it can lead to groundwater contamination.

"Keep these spray guidelines in mind when selecting a pest control for your landscape," said Smith. "Monitor and identify the pest early. Consider your control options.

"Remember, your control selection may not be what your neighbor would choose. Be a responsible gardener and ask yourself 'to spray or not to spray?"

Smith added that it is important to read the label of chemical pest controls to note the necessary steps for bee protection. "Avoid spraying insecticides when bees are active," she said.

Source: Martha A. Smith, Extension Educator, Horticulture,

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