Farwell To An Old Friend

2000 proved to be an interesting year for pesticides in the regulatory arena. Whatever your opinions are and despite what science says or does not say, chlorpyrifos (Dursban) served us well as a staple within our industry for more than 25 years. Many of those who did not see the writing on the wall (or who were unwilling to accept the inevitable) have had to make some changes.

That the industry virtually lost another entire class of insecticides — organophosphates — is one of the most unfortunate aspects of losing the use of chlorpyrifos. Other organophosphates, such as diazinon and malathion, while still available (although they are under review by the Environmental Protection Agency), are not widely used in the industry because of their restrictive labeling. Within the past year, another class of insecticides, carbamates, virtually bit the dust with the "voluntary" cancellation of Ficam (bendiocarb) and the earlier limitations placed on the use of propoxur (Baygon).

RESISTANCE ISSUES. In the past, one of the key elements in managing cockroach resistance was to have several classes of insecticides available that allowed products in different classes and with different modes of action to be rotated periodically. For pest management companies that have relied on crack and crevice or baseboard spraying with liquids, this year’s loss of chlorpyrifos leaves them with pyrethroids and diazinon (historically an active ingredient with significant resistance problems).

To manage resistance effectively, spray companies must now consider shifting to baits when pyrethroids fail. Today, the baits are almost the only option when a change in insecticide class is warranted. A wide range of active ingredients, such as fipronil, hydra-methylnon, avermectin, boric acid, im-idacloprid and diazinon are used in baits; each has a unique mode of action. An additional benefit, when using baits, is that German cockroach resistance is rare.

Resistance in flies and mosquitoes typically is more problematic than in cockroaches because of their short life cycle (often less than 10 days) and thus, high reproductive potential. With regard to materials available for flies and mosquitoes, there are even fewer options and most of them are pyrethroids. While chlorpyrifos was not widely used in this market, it was an option.

TROUBLED TERMITES. Termites will be the pest management market hardest hit by the "voluntary" chlorpyrifos cancellation in July. Chlorpyrifos has been the termite industry workhorse since the "voluntary" cancellation of chlordane in 1988. Yes, Velsicol also "voluntarily" canceled chlordane and not surprisingly, the terms of the cancellation are similar to those in the chlorpyrifos agreement.

The July agreement between the registrants (Dow AgroSciences and six others) cancels the use of chlorpyrifos as a full barrier treatment in post-construction applications. Chlorpyrifos can be used as a spot and local treatment for termites until Dec. 31, 2002. Although production of products with this labeling will cease at the end of this month, the product will continue to be sold to PCOs until Dec. 31, 2001.

Pretreatment labeling for subterranean termites remains unchanged until Dec. 31, 2005. However, prior to this date the registrants have the opportunity to produce additional use and exposure data that supports this use. Ironically, Velsicol was offered a similar opportunity with chlordane. To no one’s surprise, the chlordane studies were never conducted; thus, the effective end-use date for chlordane was April 15, 1988, one year after Velsicol’s "voluntary" cancellation — although another five years passed until the registration was fully canceled.

There is no reason to expect a different outcome with chlorpyrifos. There are other products in the marketplace that, while having slightly different modes of action, are used as repellent barriers to deny termite access to wood within the structure.

ALTERNATIVES. There are two other soil-applied products that are becoming strong players in the termite market — and for good reason. Premise and Termidor are non-repellent materials that, although they have different modes of action when applied at a high enough concentration, kill termites; both have the potential to eradicate colonies. This is radical departure from traditional termiticides that might eradicate a colony only if there was a direct hit.

Both products are applied using a cloned label from repellent termiticides. Unlike repellent termiticides, these products do not immediately stop termites from foraging into the structure; therefore, some damage might continue to occur for a short period of time. However, Termidor and Premise typically work quicker than the baits.

The success of baiting is dependent upon the termites finding the monitor and/or bait and consuming enough to affect the colony. This takes time — time that typically is the major concern of pest management professionals and their customers. But baits offer several advantages over repellent and non-repellent termiticides. Their application is noninvasive and rarely requires any drilling and pesticide application inside a structure. Most products place the technician at the customer’s home at least four times a year, which increases the opportunities for add-on services. Baits have the potential for colony eradication.

GOODBYE. Chlorpyrifos was a good product that served us well. However, over the past few years, it became obvious that to use it was politically incorrect. EPA, in its "voluntary" cancellation agreement with Dursban registrants, has affirmed this political incorrectness, which will undoubtedly heighten consumer concern about past and future use of the product. Pest management professionals should think about their pesticide choices and do what is best for their company. There are a host of good alternatives if PCOs choose to take that option.

The author is technical director of American Pest Management, Takoma Park, Md. He can be reached at rkramer@pctonline.com or 301/891-2600.