Natural and Engineered Pest Management Agents - ACS Publications

Chapter 36

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Effect of Regulation of Pheromones as Chemical Pesticides on Their Viability in Insect Control Terry D. Spittler Cornell Analytical Laboratories, New York State Agricultural Experiment Station, Cornell University, Geneva, NY 14456-0462

Mating disruption of insect pests in agricultural production by application of insect sex pheromones from point source dispensers has the potential for supplanting many chemical pesticide applications, as do several other pheromone strategies. A large number of insect pheromones are being evaluated or proposed for registration as commercial pest control agents. But, each component, under current regulations, must be subjected to much the same testing and toxicity standards as potential chemical pesticide active ingredients; this threatens to price pheromone registration beyond economic reason. High species specificity, formulation complexity and low per hectare rates all limit the market viability of a given pheromone: if registration costs are also high the product is dead. Recent proposals to ease the pesticide registration requirements for "low-risk" biorational schemes are flawed in that the unequal enforcement provisions are unfair and probably illegal, plus they reinforce the pheromones/pesticide connection. Unless and until pheromones are removed from regulation as chemical pesticides, there will be no significant replacement of high-risk pest control chemicals by pheromones. It is always a little disheartening when one of the last speakers on a program is left with the task of assessing the survival odds of the programs objectives. It would be wonderful to be able to present in-summary remarks that the business endeavors and research interests of the participants had brought us to a new era of safe, effective agricultural pest control, one that would prosper in an age of informed consumers and enlightened regulators. Sorry. Things are not so bleak that insect control using pheromones is in danger of disappearing entirely — there will always be a few token studies (funded studies) and yet another business venture; but survival is a very subjective condition, varying from minimal existence to prosperity. We are selfish, we are primarily interested in prosperity, or at least in having a chance at prosperity by building an effective and vigorous pest control option at competitive, affordable

0097-6156/94/0551-0509$06.00/0 © 1994 American Chemical Society In Natural and Engineered Pest Management Agents; Hedin, P., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1993.

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costs per acre and with minimal adverse health and environmental effects. A return on investments would also be nice. Perhaps I should qualify the balance of my remarks by noting that I, personally, am probable not destined for prosperity in this industry; in fact, I have only an indirect interest in its growth through the professional exercise of developing residue analytical methods for pheromone components and as a participate in the IR-4 Minor-Use Pesticide Registration Program, a program active in both conventional chemical and biologically based pest control strategies. I point this out to define my position not as a pheromone entrepreneur or biocontrol activist, but only as an interested scientist and indirect participant. The Problem In Perspective I don't want to parrot any one of the numerous excellent historical reviews of pheromone identification, development and deployment; even more, I don't want to abstract several and burden the world with yet another. However, I do wish to comment that as a chemist, with little agricultural or pest control training, I found it difficult to establish and maintain perspective among the many reports of specific pheromone elucidation and uses over the years. Quite frequently, I was confused as to the scale, duration and registration status of reported uses. What this did illustrate for me was the magnitude of the regulation problem, the endless combinations of simple chemical components that might be incorporated into successful pheromone insect control strategies. Not only are there hundreds of known pheromone components, many of which are common to more than one insect species or group, but they may be formulated into an infinite number of mixtures in attempts to duplicate known pheromones, or at least to elicit the desired response from the target organisms with approximations of what the natural pheromones are believed to be. Clearly, one key to establishing a successful pheromone crop protection industry will have to be the flexibility to tailor commercial preparations for rapid response to changing selectivity demands and pest behavior (7,2). In the chemical pesticide arena, this situation is analogous to allowing carte blanche introduction of numerous chemical pesticide formulations composed of combinations of all known active ingredients or of compounds having similar functional groups and characteristics. Clearly, this latter would never be allowed, and for good reasons, however, for pheromones, there are few good reasons not to allow it — only policy. Overregulation is unnecessarily stifling biorational pest control well before registration for sale and use. Research and testing are delayed or made prohibitively expensive by EUP (Experimental Use Permit) requirements enacted for high-risk pesticide testing. Now they serve as de facto barriers to development of all materials except potentially high volume, high profit (high-risk?) chemical pesticides. Some token concessions have been made, but regulatory demands are still formidable, even in light of EPA's 1982 guideline establishing the tier testing scheme to limit data requirements to those on the first three tiers in the absence of adverse effects from tier one testing, and even with the provisions for waiver of data generation for information not deemed relevant for hazard evaluation of the subject product — assuming, of course, that sufficient acceptable data demonstrating the need for no data are presented to support the initial waiver request. A little more than this is needed. Reduced Risk Approach This talk had been in preparation only a short time when the EPA's July 14, 1992 proposal "Incentives for Development and Registration of Reduced Risk Pesticides" was released for public comment and, at first blush, took some of the urgency out of what I had intended to discuss (3). There is always a danger when preparing to

In Natural and Engineered Pest Management Agents; Hedin, P., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1993.


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discuss government policy that one's thoughts or points will be rendered obsolete by presentation time. Not that obsolete thoughts are forbidden (or even unusual) at these exercises, it's just that one hates to admit them at the outset. Here possibly was the answer to the registration obstacles in the path of pheromone insect control. Had a prescient answer (in the affirmative) been received to my title rhetorical question, "Will insect control using pheromones survive regulation?" Unfortunately, reflection on this document revealed provisions that would certainly elicit unfavorable responses from several quarters. These would make its adoption unlikely. Further reflection on this document revealed consequences to the pheromone industry (and other reduced risk endeavors), as well as to agricultural in general, that would be disastrous if it were implemented. The former are more obvious: 1) It would be blatantly unfair to rank pesticides according to perceived risk or environmental correctness and then selectively and preferentially apply the FIFRA mandates to their registration, reregistration or continued existence. All pest control chemicals, once they have qualified for the definition of "pesticide" are subject to and entitled to all the provisions of FIFRA as they pertain to their regulation. While it would certainly be reasonable and allowable to waive irrelevant and/or redundant data requirements, EPA is required to review all pesticides equitably. 2) Market manipulation by private firms, either individually or by collusion, to give products an unfair competitive advantage is rarely desirable and frequently cause for intervention by one or another regulatory agency. Market manipulation by a regulatory agency, by means quite outside its legislative mandate, to achieve ends that are based on highly subjective evaluations of relative safety, would be, regardless of the purity of intent, even more objectionable. 3) Identification of any pesticide as high-risk for the purpose of identifying areas or uses for which lower risk alternatives would receive prompt and preferential consideration would elicit activist demands for its immediate removal from commerce, regardless of its other merits, regardless of whether or not a suitable replacement had been introduced. In fact, zealous attempts to replace a compound might result in the forced substitution of ineffective materials causing devastating losses of income and markets. 4) It is improbable that we can ever completely replace chemical pesticides with biorational control strategies. In fact, knowledge that several old "high-risk" control options remained available for intermittent, emergency use could give growers the security to try more biological control strategies for a major portion of their needs. Of course, there would have to remain enough of a spot market to justify continuance of a label for these emergency uses. This might require some concessions or relief from high yearly maintenance fees, if enacted. Since effective IPM programs also require occasional surgical strikes, the loss of many "high-risk" materials would make inoperative many schemes relying upon them for crisis management or threshold response (4). In addition, control of resistance development depends heavily on the available of alternatives. These critical uses for our proven chemical pesticides must be preserved so that safer more biologically compatible materials can assume major (but never exclusive) roles in crop protection. Reducingriskassessment to simple terms,risk=


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'Xicity χ frequency, many of the targeted "highrisk"chemicals could be scored ery benevolently if only used when absolutely necessary, and then, of course, with the exercising of all due caution against worker exposure and environmental damage. In essence, our best interests lie not in eliminating the "high-risk" compounds, but in minimizing unnecessary application, in confining their use to those situations where a "low-risk" biorational scheme falls short. The second facet of EPA's "Incentives..." proposal, the one that I previously stated as being potentially disastrous for pheromone pest control efforts, is that by accepting a few minor concessions in the pesticide registration process, the agricultural community legitimizes the inclusion of pheromones as chemical pesticides. Under a fundamentalist interpretation of pheromones as chemical formulations applied in acreage known to be inhabited by food producing plants, they are entitled to the full benefits of attention by the EPA Office of Pesticide Programs, Registration Division. Unfortunately, this gives pheromones equal standing with aldicarb, benomyl, carbofuran and on and on. The inclusion of pheromones in this company is arbitrary, arbitrary because it automatically ascribes to pheromones all the toxicological and environmental detriments historically associated with classical chemical pesticides. In so doing it assigns an unreasonable registration burden to a group of potential pest control agents, having in addition to low toxicity and environmentally benign chemical characteristics, a spectrum of specificity and use strategies that sets them as far removed from chemical pesticides in eradication campaigns as phosdrin and fly swatters.

What Pheromones Are And Are Not What is not being acknowledged is that the behavior modification mode of pest protection, a classification into which pheromone schemes fit much more closely then they do that of chemical pesticides, does not impart the directed toxicological risk or non-target environmental effects that drive the chemical pesticide registration process. Consider for a moment some similarities and differences: 1) pheromones are not applied directly to any part of the horticultural product system as are chemical insecticides, fungicides and occasionally herbicides, but are introduced as minute quantities of volatiles via noncontacting dispensers strategically placed throughout the planting: more like rows of marigolds placed along garden borders and between rows to release numerous volatile compounds that seem to minimize insect infestation. 2) in fact, insect pheromone components are probably considerably less potentially detrimental than marigold components which actually repulse insects. Pheromones are simply the essence of a communications system unique to the pest(s) being controlled. There may be a few pheromone components that have objectionable properties or would be considered dangerous or undesirable if residues were significant, but a major point about lepodopterian insect sex pheromone compounds is that almost invariably they are long-chain fatty acids, alcohols, acetates, aldehydes, saturated and unsaturated, usually straight, but occasionally with branched or annular structure: in short, they are similar or identical to naturally occurring fats, waxes, flavors and odor causing compounds found and consumed throughout the plant and animal kingdoms (i.e. our food chain) at orders of magnitude higher concentrations than man-made pheromones would ever be employed in a mating disruption program.



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513

In our poster presentation earlier in this conference we reported finding dodecenyl alcohol and tetradecenyl alcohol in four varieties of untreated apples at concentrations ranging from 70-130 ppb. The natural occurrence of these compounds in apples had been reported in 1976, but not quantitated (5). The irony is that they are two of the five components in an experimental lepidopteran insect sex pheromone for which residue determinations were made of all components on treated apples. This full season application included 52 g/ha and 10 g/ha of dodecenyl alcohol and tetradecenyl alcohol, respectively. These were minor constituents, the major component was 106 g/ha of E,E-8,10-dodecadien-l-ol. No increased levels of the saturated alcohols were detected in fruit from treated orchards, and none of the latter, major component, was detectable above 10 ppb, our level of sensitivity (Spittler, T. D., Leichtweis, H. C. and Kirsch, P. Manuscript in preparation). The specifically of the selective-ion monitoring employed in our gas chromatographic/mass spectral analyses (GC/MSD/SIM) is such that primarily the programmed pheromone compounds are quantitated and confirmed as being present or absent (6,7). Other, similar chemicals that might also be present are not always detected and identified, so we do not know all other compounds similar to insect pheromone components the apples are producing. However, these data do encourage speculation that some plants might be producing disruptive levels of insect sex pheromones as a defense mechanism — presumably without EPA's authorization. Pheromones As Biological Buffers The strategy to minimize the use of high-risk chemical pesticides by encouraging their replacement with more benign compounds through the vehicle of easing the pesticide registration requirements of biological control systems, including behavior modifying insect pheromones, is only a hollow gesture that will do little to foster the successful use of pheromones for insect control. In fact, making concessions to pheromone registration as pesticides is perhaps committing a serious error in locking them into that classification: by entrenching the concept, it becomes more difficult to remove, as a class, for example, all non-lethal biological formulations composed of natural or natural-like compounds of demonstrably insignificant toxicity, from the definition of pesticide, and into an entirely separate classification called, for sake of illustration, "species specific buffers". Buffer would be, in fact, a much better term for a biological control strategy because the objective is rarely the active eradication of a pest species or spectrum by application of a toxic compound, but rather the intent is to cushion the impact of a biological proliferation, i.e. the target pest population, and tip it towards economically acceptable, or threshold levels. Neither pathogens, behavioral disruptions nor induced predators will bring about the eradication of a pest species. They only serve to keep populations at levels compatible with local horticultural practices. Does that make them pesticides? Yes, if we want to call them that. No, if we find it more advantageous not to. There is no absolute that establishes what is a pesticide — there is no absolute that establishes what is not. We currently live with definitions derived as a compromise between scientific evidence, political expediency and the interests of the consumer. All of these three factors are constantly being reweighted. So why should the pesticide definition remain insulated from evidence and influence?


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We Are Standing In Our Way We would like to think that the agencies responsibility for regulating many aspects of our lives, including our food supply and environment, have the foresight and latitude to respond to changing knowledge and changing needs. Certainly we cannot recommend a disregard for legislated standards, but we live in an era of fundamentalist interpretation of statutes. Note specifically the recent interpretation that the Delaney Clause, by virtue of being the letter of the law — anachronistic as that letter now is considering its far remove from its inception — will continue to proscribe the trace residues of benomyl, captan and several other important chemical pesticides in processed foods, this despite the interpretations of negligible risk repeatedly espoused by responsible agencies and designated advisor groups. It is precisely situations such as this that make me pessimistic that we will ever achieve real progress in biorational control as long as it is strictly regulated in concert with chemical controls. Of course, now and then a new pheromone or other biorational registration appears, but it is usually either one of the few high profile, heavily researched uses (e.g. grape berry moth pheromone) or it has been extensively subsidized by venture capital and/or public funds in yet another demonstration splash that hopes to propagate the wave of the future. I am sorry, but I see no future for insect control using pheromones ever supplanting conventional chemical controls as long as pheromone formulations are defined and regulated as pesticides. There are hundreds, perhaps thousands, of known pheromone components that occur naturally in an infinite combination of product and proportion. Not only does each insect species require a unique mixture of known and available materials, properly employed, to have its mating, aggregation or other cycles disrupted or diminished, but the flexibility to fine tune composition for maximum efficacy is also essential. What we have brought upon ourselves is a situation where the hypothetical protection of a commodity from an insect pest using pheromones requires that toxicological data packages for several materials be completed (average three compounds per pheromone) and that residue studies for all components in each formulation be conducted in significant growing areas of the commodity. By contrast, one broad spectrum N-methyl carbamate or versatile organophosphate material can obliterate dozens of insect species on our same hypothetically commodity for the price of one toxicology package for a parent and perhaps a metabolite and the same designated-site residue studies. Is there perhaps another price being paid here? Literature Cited 7. Nabholz, K. In Behaviour-Modifying Chemicals for Insect Management; Ridgway, R. L., Silverstein, R. M. and Inscoe, M. N., Eds.; Marcel Dekker Inc.: New York and Basel, 1990, pp 553-555. 2. Tinsworth, E. F. In Behaviour-Modifying Chemicals for Insect Management:; Ridgway, R. L., Silverstein, R. M. and Inscoe, M. N., Eds.; Marcel Dekker Inc.: New York and Basel, 1990, pp 569-601. 3. U. S. Environmental Protection Agency, 57 Fed. Reg. 32140, (July 20, 1992). 4. Shani, A. Role of Pheromones in Integrated Pest Management; 1992 (unpublished survey).


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5. Van Straten, S. Volatile Compounds in Food, 4th ed.; Central Institute for Nutrition and Food Research: Zeist, Netherlands, 1977. 6. Spittler, T. D., Leichtweis, H. C. and Dennehy, T. J. In Biotechnology for Crop Protection; Hedin, P., Menn, J. J. and Hollingworth, R., Eds.; ACS Symposium Series No. 379; 1988, pp 430-436. 7. Spittler, T. D., Leichtweis, H. C. and Kirsch, P. In Insect Pheromones and Other


Behaviour-Modifying Chemicals: Applications and Regulation; Ridgway, R. L.,

Inscoe, M. and Arn, H. Eds.; British Crop Protection Council; 1992, 51; pp 93108. RECEIVED August 19, 1993


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