Many of our office visitors often want to know what landscape pesticide they can spray to kill a particular pest.  They also don't want the product to harm the plant they are protecting.  In many cases the University of Florida has recommendations for their situation.  But sometimes, the visitor goes away unsatisfied because there are no "silver bullets" that can legally accomplish what they are seeking. And because of recent legislation, many products used in the past are no longer labeled for their situation.

Today's column will discuss how some pesticides can selectively target certain pests without harming the protected plant, while others are "broad spectrum" pesticides used to manage a wide variety of pests.  The correct choice can spell the difference between proper pest management and environmental damage.

EFFECTIVE WEED KILLERS

Pesticide are useful tools that can save time and money when properly used.  A selective pesticide is one that will kill certain specific pests, but will not harm other non-target organisms.  A good example is one of the oldest weed killers still on the market today: 2,4-D.  When using this product according to the label on grassy-type plants (corn, sugarcane, or turfgrass), it will have few effects on grassy plants.  However, it will disrupt the growth of broadleaf plants (dollarweed, clover, or tomatoes) and is useful as a broad-leaved weed killer where the grassy plants are being grown.

Selectivity allows a pesticide it to be used where one plant fills an area, such as in a pasture or a lawn.  Allowing such products to drift into non-target areas may result in damage to unintended plants.  It is imperative that proper application methods as stated on the label are closely followed.  Pesticide selectivity also depends on the timing or the rate of application.  Here are some examples:

• The label for 2,4-D allows it to be used on turf only when temperatures are below 80 degrees F; it will burn the turf if used in summer temperatures.

• Atrazine can only be applied twice per year, and must be kept from the root zone of desirable ornamental plants.

Pesticides that can kill any pest are called broad-spectrum or nonselective pesticides.  A good example is glyphosate, the popular weed killer known as Roundup^TM.  It will damage or kill almost any weed plant when used according to the label.  To keep it from damaging desired plants, carefully apply it only to the weeds.

Many herbicides have been shown to provide selective control of certain weeds.  However, the companies that develop these products have to examine the potential profit if they develop a product for certain markets.  If costs outweigh the returns, or if there is a limited market for a pesticide, it will rarely be developed.

Here's why: the Food Quality Protection Act  now requires that risks of exposure for a particular pesticide must be evaluated.  If the EPA feels that the risks are too high, certain uses will not be allowed.  A company might choose to drop certain uses to reduce the potential exposure to that pesticide, especially if children or homeowner applicators are involved.  Risks to these populations are major reasons why companies have dropped some of their homeowner products.

While gardening enthusiasts may tire of hearing it - the label is the law.  Read and follow all instructions before buying and before using any pesticide. Know what the pest is that you are aiming to kill - and be convinced it is causing the problem you are dealing with. Be sure that the product says that it can be used where you intend to apply it.  I recently visited a home where a tree was killed - I suspect that the damage was due to the misuse of a product designed for fence row weed control was used in the root zone of the tree.

Consider hiring a pest management company to assist you.  Ask them to tell you what product they are using.  You may want to ask for a copy of the pesticide label to fully understand how the product is legally used.  If they can not give you a copy, ask our office how to obtain one.

If you need additional information on proper pesticide use, call or stop by our office at 458 Hwy 98 North. Our phone number is 763-6469, and you can email us at okeechobee@ifas.ufl.edu.