Are you prepared to lose your OP shield?

CHANGE best describes the turfgrass industry during the past 20 years, as well as what we can expect for it in the future. This is especially true as a result of the Food Quality Protection Act of 1996 (FQPA). FQPA requires the Environmental Protection Agency (EPA) to review all pesticides according to newer, more stringent standards than in the past. The expected result is the loss of many of the pesticides that turf and landscape managers have relied on for decades, especially from the organophosphate (OP) and carbamate classes.

To date, the FQPA has resulted in the phase-out of several organophosphate and carbamate insecticides, and more losses are expected. The EPA is currently reviewing data for methycarbamates (e.g., carbaryl), chloroacteamides (e.g., metolachlor), thiocarbamates (e.g., EPTC and pebulate) and triazine (e.g., simazine and PCNB) chemical groups.

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The FQPA and its implementation by the EPA have been controversial. Among other things, FQPA requires more stringent “default” margins of safety for chemicals unless manufacturers can prove that the stricter standards are not necessary — a sort of “guilty until proven innocent” approach. In some cases, the manufacturer simply opts to pull a product from the market because the additional testing required to demonstrate its safety costs more than the product will be able to recoup.

Further, the FQPA requires that EPA assess cumulative risk, which assumes that chemicals within a given class (OPs, for example) have a common mechanism of toxicity and should be evaluated together, almost as if they were the same chemical. The concept of cumulative risk is controversial. In addition, the EPA is struggling to create the science necessary to evaluate chemicals in this manner, so it's anyone's guess what the outcome will be.

Regardless, the FQPA is here to stay and it will undoubtedly force the removal of more pesticides from the market. Unfortunately, some of these products have been the foundation of consistent and reliable turfgrass pest management programs. As a result, turf and landscape managers must consider alternative control products that are effective, economical and pose minimal environmental risk.

Second best, or just best?

Though some of these chemicals are significant losses, circumstances are not as bleak as they may appear. Agricultural chemical companies continue to discover, develop and market products from new classes of chemistries. These newer chemicals are characterized by high target-specificity, lower application rates (thus, reduced chemical load) and reduced risk of adverse, unintended effects.

Regardless of the pest type (disease, insect or weed), understanding the biology (life-cycle, behavior, etc.) is the key to successful pest management, particularly with the newer products. With the relatively narrow spectrum of control they exhibit, sampling and monitoring as well as accurate identification of turf pests become even more important for effective control. (That is not to say that they aren't important now!)

Newer chemistries also provide control products designed to be effective with levels of active ingredient much lower than older chemistries contain. For example, many of the synthetic pyrethroids (e.g. bifenthrin, cyfluthrin, deltamethrin and lambda-cyhalothrin) are applied at the rate of 0.1 pounds active ingredient per acre. Compare this to the organophosphate chlorpyrifos (Dursban), which is applied at 1.0 pounds active ingredient per acre. This means that the overall chemical loading is reduced by 0.9 pound per acre while still achieving effective insect control.

In addition, many of the newer control products have considerably lower mammalian toxicity and less residual activity, which may reduce their environmental impact.

What control options are available and effective?

As control products continue to be removed from the market, it is inevitable that some will be irreplaceable. However, in most instances alternative products are available. One of the most important questions is: Are the alternatives effective? The answer, happily, is yes! In fact, in most cases, “replacement” chemistries have been shown to provide equivalent or even better performance.

For example, compare two preventive grub-control products, isofenphos (Oftanol — being phased out) and imidacloprid (Merit). Imidacloprid is a superior choice for preventive control for several reasons. First, imidacloprid is applied at a rate of 0.3 pound per acre, whereas isofenphos was applied at 2.0 pounds per acre. Second, imidacloprid has longer residual activity and a higher efficacy rate than isofenphos. Finally, imidacloprid has an oral LD50 of 2,591 and isofenphos has an oral LD50 of 32.

LD50 is a measure of toxicity and refers to the dose — measured in milligrams of toxin per kilogram of bodyweight — that will kill 50 percent of a population of lab animals. Thus, a lower LD50 value indicates a higher toxicity. The table at left shows the LD50 of several common substances as well as some pesticides. Not only does this comparison put pesticide toxicity in perspective, it also illustrates the axiom “the dose makes the poison.” For example, caffeine, consumed daily by millions in the form of coffee, is considerably more toxic than most pesticides for turf and landscape use; aspirin is slightly more toxic than malathion.

Several insecticides labeled for turf use that have been (or may be) removed from the commercial market (or at least certain uses will be eliminated) include acephate, bendiocarb, chlorpyrifos, diazinon and isofenphos. The table on page 16 contains a list of these and other older insecticides that have been or may be eliminated or restricted by the EPA, and newer products that are viable alternatives.

As professional turfgrass managers, to be successful you must stay abreast of any changes in product registration, replacement products, their chemical classes and mode of action (to minimize possible resistance), pest-control spectrum, effectiveness, cost per acre, environmental impact and well as tank-mix compatibility with other control products. As the choices of products continue to evolve, such information becomes even more important for successful pest management. To keep current with pesticide registration, labeling and efficacy information, contact your local county extension agent or state university specialist. Specific label and MSDS information can be obtained from manufacturers or product formulators as well as Internet websites such as www.cdms.net.

Dr. R. Chris Williamson is a turfgrass and ornamental specialist with the Department of Entomology, University of Wisconsin-Madison.

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