Get It Growing: Use Insecticides Only When Necessary

Daniel Gill, Merrill, Thomas A.  |  2/27/2007 4:15:59 AM


Get It Growing News For 03/09/07

By Dan Gill
LSU AgCenter Horticulturist

Pest problems will become more common as we move into the warmer summer moths.

Although some gardeners still feel they should immediately get an insecticide and begin spraying when they see insects or apparent insect damage in their gardens, just seeing an insect or insect damage is not reason enough to spray.

By doing so you may end up killing beneficial predatory insects that are eating pests on your plants, and this actually can cause pest problems to develop or become worse. In such a case, you will have wasted time and effort and destroyed a friend rather than a pest.

The insects you see may not be harmful, or they may not cause enough damage to warrant the use of an insecticide. Or if the damage you see is old, then the pest that caused it has already come and gone, so spraying won’t do any good.

Even if using an insecticide is the right course of action, it is very important to use it the right way.

The initial step in deciding how to control a pest is to correctly identify the insect causing the damage and to determine if those insects are active now or if the damage is old. Then decide if the amount of potential damage warrants control and see if there is a way of controlling the pest without the use of pesticides.

Integrated pest management or IPM (also known as least toxic pest management) is the most practical approach for most gardeners. This "middle-of-the-road" method relies on the regular monitoring of pest populations to determine if and when to take action. Nontoxic strategies for control are used first, including physical, mechanical, cultural and biological methods. When all else fails, pesticides with the least toxicity and environmental impact are selectively applied.

When using an insecticide it is very important to identify the insect causing the damage. Otherwise, you may use the wrong material. No single insecticide will control all insect pests.

The pesticides we use in our home gardens generally are short-lived – to reduce the chance of environmental problems from residues. Most insecticides break down in a matter of days after application and offer no protection after that.

Of course, that means you can’t spray once in the spring and expect your plants to be protected indefinitely. After controlling an insect infestation with an insecticide, don’t be surprised if you need to spray again later on in the season. Pest problems can, and often do, recur. It doesn’t mean what you originally used was not effective – you just need to do it again.

It is essential to read the entire label before purchasing a pesticide (and again before using it). This is the best way to be certain it will control the pest situation you are dealing with. If the label does not have specific information regarding the way you intend to use the pesticide, put it back and find a product that does.

Say, for instance, you’re told to control a lawn insect with acephate. If the container of acephate you first pick up has information on how to use it on ornamental plants and nothing about lawn applications, put it back and find a product containing acephate that does have information on how to apply it to the lawn.

The label also will tell you how much to use and how to mix and apply it safely. Pay careful attention to the safety precautions that must be taken – such as wearing protective clothing. Some pesticides have restrictions for use on certain plants and at certain temperatures. If you don’t follow those restrictions, you might cause the plants damage rather than helping them. You should read all of this before you purchase the pesticide!

Also, find out which effective pesticide is the safest and least toxic. Check the label of the pesticide container for one of three words. Caution denotes the least toxic category of pesticides. Warning appears on the label of the next most toxic category, and Danger is on the label of the most toxic category of pesticides.

When purchasing, always buy the smallest available container of a pesticide so that you will use it up faster. Pesticides lose potency over time and most of us have too many bottles of pesticides sitting on shelves already. If you are given a recommendation to use something you don’t have on hand, ask if one of the insecticides you already have would do the job. It’s best, whenever possible, to use up what you already have.

Keep in mind, too, that the control method must be directed toward the pest. If the insect lives and feeds on the underside of the foliage, your spray should be directed there. If it lives on the trunk and branches, a light spray on the foliage will not be effective. Only spray infested plants and those nearby of the same kind. Do not spray everything in your landscape just because a few plants are infested.

If you spray pesticides when they are not necessary, you needlessly introduce toxic substances into the environment. Before you start spraying, be sure the insect is properly identified and find out if there is an effective control method that does not use insecticides.

If you decide to use an insecticide, use the right one at the proper rate with the proper applicator. Apply the insecticide according to the label directions and in a manner that will give you the safest and most effective control.

Get It Growing is a weekly feature on home lawn and garden topics prepared by experts in the LSU AgCenter. For more information on such topics, contact your parish LSU AgCenter Extension office or visit our Web site at A wide range of publications and a variety of other resources are available.


Contact: Dan Gill at (225) 578-2222 or
Editor: Tom Merrill at (225) 578-2263 or

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