Pesticide Residues and Food Safety - ACS Publications - American

Chapter 7

Pesticide-Free Tree Fruit Crops Can We Meet Consumer Demands? Patrick W. Weddle

Downloaded by COLUMBIA UNIV on September 19, 2017 | http://pubs.acs.org Publication Date: December 31, 1991 | doi: 10.1021/bk-1991-0446.ch007

Weddle, Hansen and Associates, Inc., P.O. Box 529, Placerville, CA 95667

The issue of "food safety" has, especially since the airing of the two "60 Minutes" episodes on Alar, contributed to a renewed and escalating interest in "Integrated Pest Management" (IPM). Once again, after a period of rhetorical dormancy as a regulatory and funding "buzzword", the agricultural community and other environmentally concerned groups are revisiting IPM as an alternative to extensive reliance on toxic pesticides. As a long time student and "front line" practitioner of IPM, I have found this renewed interest to be both curious and provocative. Once again, integrated pest management is being "rediscovered" as that which it was always intended to be, i.e. an ecological approach to crop protection which results in a reduced reliance on pesticides (1). As such, IPM offers the most realistic possibilities for reducing and/or eliminating residues of pesticides on food crops. IPM thus holds potential for contributing to food safety. It is the practical implementation of this possibility that is the subject of this paper. All responsible definitions of IPM refer to the use of pesticides as appropriate when those uses are judicious and selective (2). Indeed, field implementation of IPM in agriculture has led to significant reductions in the use of toxic pesticides, when compared to conventional spray programs, and mitigated many or most of the environmental and human health consequences of the associated pesticide use. In addition to the benefits of pesticide use reduction, yields either remained constant or increased in the crop systems studied (3). Thus, IPM implementation is a proven alternative to unilateral pesticide use and serves as a technological "surrogate" to those chemical use patterns that have resulted in actual or perceived environmental and human health problems. One of the side effects of a well-fed society is the freedom to ponder and critique the technologies that have allowed us to free ourselves from the toil of subsistence farming. The scrutiny of petrochemical technology as it is used in agriculture has led to, among other things, a growing perception that perhaps the residues of chemical pesticides on and in food

O097-6156/91/0446-O058$06.00/0 © 1991 American Chemical Society

Tweedy et al.; Pesticide Residues and Food Safety ACS Symposium Series; American Chemical Society: Washington, DC, 1991.

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products have rendered those products unsafe for human consumption. It is not within the scope of this paper to debate the food safety issues. It is appropriate, however, to illustrate how, assuming continued availability of an array of conventional pesticides, and through the implementation of multi-tactic IPM, the probability of pesticide residues can be either limited to below detectable levels or to no residues at all. To the extent that food safety can be equated to a reduction in pesticide residues on food, IPM offers a practical operational approach to advancing the safety of food.


How IPM Can Provide "Pesticide Free" Food In the current debate about food safety many equate safe, wholesome food with food that is "pesticide free". "Pesticide free" may mean organically produced to some (though "organic" pesticides are sometimes heavily used in organic farming) or free of detectable pesticide residues to others. The concept of "no detectable residues" has been adopted by some retailers with considerable marketing success and appears to be satisfying at least a segment of the consuming public's concerns about food safety. As our ability to detect ever smaller amounts of chemicals increases, the establishment of de minimus standards may be required to ensure meaning to "no detectable residue" as a marketing concept (4). The most current data from the pesticide residue monitoring program conducted by the California Department of Food and Agriculture (CDFA) showed that 78% of the 9,293 "Marketplace Surveillance" samples tested were free of detectable pesticide residues. Furthermore, residues less than 50% of tolerance were detected in 19% and illegal residues in 1% of the samples. (5). These marketplace data mirror results obtained from CDFA's "Priority Monitoring", preharvest monitoring and monitoring of residues on produce destined for processing. Though currently used CDFA screening methods are capable of detecting only 1/3 to 2/3 of the pesticides registered for food use (6), they, nonetheless, can be viewed as an indicator of the potential for petrochemical contamination in the California food supply. On the basis of these data, if farmers could target bio-intensive IPM efforts on the crops containing the 20% of the pesticide residues that are currently being detected, these residues could also be reduced to below detectable levels or eliminated altogether. To accomplish an operational program of reducing or eliminating the potential for detectable residues on fruit crops, our firm takes a 3 pronged approach. First, information on the degradation curves of the pesticides of potential use needs to be known. These data are not readily available. Consequently, we make assumptions based on what we know from pesticide residue monitoring data and from the chemical properties of the pesticides under consideration for use. This information allows us to make gross estimates of the field degradation time of a given pesticide.



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PESTICIDE RESIDUES AND FOOD SAFETY

Secondly, the intensive biological and environmental monitoring component of our IPM program allows us to use the selected pesticides in optimal amounts which often result in reduced applications compared to more preventative approaches. When pesticide intervention is determined to be necessary, selected chemicals can often be targeted to individual blocks within the orchard rather than spraying the entire orchard. Monitoring information also allows us to successfully utilize pesticides at reduced rates. Knowledge of residue potential motivates us to select pesticides and precise spray timing to manage low levels of pests, earlier in the season, with lower amounts of chemicals, far enough in advance of harvest to mitigate the possibility of a detectable residue. Finally, we are beginning to gather data on residue testing. By knowing what residues are being detected in CDFA monitoring and with residue data gathered on our client crops (for which we have valid pesticide use data), we can draw conclusions as to which chemical use strategies will mitigate detectable residues at harvest. With the new comprehensive pesticide use reporting regulations beginning in 1990 in California, the ability to tie residues to pesticide use patterns will be further enhanced. Guthion: An Operational Example. Guthion (azinphosmethyl), an organophosphate insecticide, has been the material of choice for codling moth control in most of our client orchards over the last 15 years. In spite of its broad spectrum biological activity and acutely neurotoxic properties, azinphosmethyl, when used in the context of our IPM programs, has allowed us to safely and effectively control codling moth while minimizing the secondary, pesticide induced pests that commonly require additional applications of broad spectrum pesticides. Guthion 50% wettable powder is typically packaged in 1 lb. dissolvable packets. Workers who load and mix Guthion drop these packets into partially filled sprayer tanks while wearing regulation safety equipment which includes respirator, eye protection and full body protective clothing. Risk exposure from mixing and loading of Guthion insecticide is virtually nonexistent where mixers—loaders have had the required training and use the required safety equipment. Furthermore, regulation requires the applicator to wear full safety equipment. Grower concerns for the health of their workers coupled with ever increasing monitoring of spray operations in California, further ensures worker safety. Improved monitoring of spray operations by California Agricultural Commissioners has forced compliance with regulations regarding off-site drift. Our grower clients and their applicators are very aware of the potential liabilities surrounding drift of pesticides into not-target areas and are making every effort to eliminate drift hazards. Within the orchard ecosystem there occurs a predatory mite which has developed a high level of resistance to Guthion. We routinely monitor for the presence of this predatory mite. We also monitor for the plant feeding mites that typically are the focus of chemical use in non-IPM orchards. We know that the predatory mites will usually maintain the pest mite species



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below levels that threaten economic loss when ratios exist of between 1 and 2 predators per 10 phytophagous mites. By not eliminating the phytophagous hosts completely with chemical miticides, by careful use of pesticides such as Guthion, by using reduced rates of selected pesticides, by reducing orchard drought stress through systematic soil moisture monitoring and irrigation management and by routinely monitoring the arthropod populations in the orchard environment, we have been able to maintain Phytophagous mites at non-pest status in most orchards, in most years. This has occurred without reliance on chemical miticides. The CDFA summary of 94 samples targeted to azinphosmethyl residues on pears and apples at harvest (Table I), showed that azinphosmethyl was not detected in 60% of the samples. The remaining 40% of the samples had residues of azinphosmethyl that were within tolerance (5). Through the selection of the most appropriate dosage rates and with careful timing of applications, we believe that our IPM program will increase the probability of no detectable azinphosmethyl at harvest. We can extend these strategies to the use of any pesticide in our IPM programs. Because of the bio-economics of codling moth and due to the lack of proven alternatives, we are currently relegated to almost exclusive reliance on petrochemicals, especially Guthion, for managing this difficult pest. Practical alternatives are currently not forthcoming for the control of codling moth and those that do show promise (e.g. mating disruption with pheromones) will probably not provide the levels of pest suppression expressed with chemical pesticides. Thus, in addition to exploring feasible alternatives to petrochemicals, fruit growers are interested in preserving azinphosmethyl and are becoming interested in eliminating the potential for detectable residues of this and any other pesticides on their produce. Other Operational Examples of IPM-Based Pesticide Use Reductions. Because IPM is an information based crop protection system, information developed becomes knowledge when properly interpreted. This knowledge, in addition to optimizing the use of pesticides, becomes a substitute for pesticide use further reducing the need for preventative pesticide applications and enhancing the possibility for a "no detectable pesticide residue". Table I. Results of the CDFA Focused Monitoring for Azinphosmethyl in Pears and Apples during 1988 Pears

Samples t a k e n Mo r e s i d u e s Residues i n Residues out Tolerance Range Avg. r e s i d u e Median r e s i d u e

59 38 21 0

Apples

JL

_JL 100 64 36 0 2. 00 ppm 0 -1 .00 ppm 0. 27 ppm 0. 30 ppm

35 20 15 0

-A 100 57 43 0 2. 00 ppm 0 -1 .70 ppm 0. 74 ppm 0. 37 ppm



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A recently completed 3 year study conducted under commercial pear production conditions showed that a pilot IPM approach, similar to the one described in the previous example, resulted in an average pesticide cost savings of $141.00 per acre compared to the standard pesticide intensive program which was routine for the cooperating grower (8). Avermectin, a miticidal byproduct of antibiotic production, has recently seen extensive use in California pear orchards. The label rates range between 10 and 20 ounces of formulated material per acre. Through monitoring of mite populations, we and others have documented ample mite control at 5 ounces per acre when used with oil. At $5.00 per ounce, this results in a substantial cost reduction to the grower as well as reduction in potential resistance development. Carzol SP (formetanate) is another miticide that is commonly used to prevent certain eriophyiid rust mites that cause a cosmetic russetting of Bartlett pears. This miticide, when used at label rates of 1-4 lbs. per acre, is very destructive to beneficial arthropods including predatory mites. Our fruit monitoring program allows us to predict a pending problem with rust mites. When monitoring indicates need, Carzol applied early, prior to the mites reaching damaging levels, can effectively control rust mites on pears with 1/4 lb. per acre. By using a rate of Carzol that is 75% below the low label rate, our growers-clients save approximately $20.00 per acre in materials, prevent economic loss, reduce worker exposure to a Category I toxin, reduce the potential of a toxic residue, reduce the potential for resistance development and minimize the destruction of bénéficiais. Pydrin 2.4 EC (fenvalerate) is a synthetic pyrethroid with broad spectrum insecticidal properties. It is very destructive to most beneficial arthropods in the orchard environment. It has been very effective in controlling one of the most destructive pear pests, pear psylla. When combined with spray oil in the dormant spray, we have been able to accomplish seasonal control of psylla in our IPM program with Pydrin at 6 ounces per acre. The label rates of Pydrin typically used are 11-21 ounces per acre. At about $1.00 per ounce the savings of $5.00-$15.00 are realized. More importantly, the lower label rate ensures very little disruption of beneficial species, reduced resistance potential and, when used exclusively in the dormant period, precludes any possibility of a fruit residue. These are but a few of the more simple examples of how we reduce or eliminate pesticide applications in our IPM programs. Constraints to Implementation of IPM and Food Safety As previously mentioned, IPM offers an operational approach to pesticide use reduction. Ironically, to accomplish this reduction efficiently requires the "appropriate" use of pesticides as an invaluable tactic (9, 10). As such, the ability of multi-tactic IPM to ensure food safety can be hampered by excessive constraints to pesticide use.



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Political and Regulatory Constraints. Recent studies conducted by the University of California Agricultural Issues Center have documented the conflicting policies as they relate to the role of chemicals in the food safety issue (11). Indeed, though consumer advocates, consumers, food processors, farmers, retailers, and environmentalists point to IPM as a desirable technology to reduce growers' dependency on pesticides, there exists little discussion of real-time, frontline implementation of IPM strategies as a component of an overall agricultural policy. Rather, the debate typically is single issue oriented and hinges upon worker safety and environmental concerns, toxicity and risk assessment, regulatory costs, economics, data gaps, research funding, etc. All participants in the debate affirm the value of food safety and the need to reduce reliance on pesticides. However, the goal of pesticide use reduction and a concurrent reduction in pesticide residues does not happen in a vacuum. Single issue legislative and regulatory efforts aimed at restricting the use of pesticides at the national and state levels have created vacuums that may actually be increasing the reliance on pesticides and other petrochemical inputs (4, 9). While the debate is waged, growers and their advisors continue to be faced with the daily realities of crop production and protection under an ever expanding umbrella of uncertainty. In California, regulatory policies of the CDFA and recent legislation have provided at least short term incentives for increasing pesticide use. Data requirements under SB 950, the Birth Defects Prevention Act, and constraints due to Proposition 65, the Clean Drinking Water Act, are resulting in the loss certain pesticide uses (potentially including organically acceptable pesticides). In the absence of practical alternatives, these losses concentrate the use of fewer and fewer pesticides on a limited gene pool of pest susceptibility. As pests become resistant to the few remaining materials and as the commercialization of pesticides becomes increasingly slower and more expensive, use of the fewer remaining pesticides will increase in the absence of alternatives. Regulations which enhance the potential for resistance to develop work counter to effective implementation of pesticide resistance management. Because resistance management is an important component of an IPM system, regulations which eliminate appropriate uses of pesticides may be counterproductive to the implementation of IPM. In the context of multi-tactic IPM, to reduce reliance on pesticides practitioners will, paradoxically, need the appropriate uses of a broad selection of pesticidal products (9, 12). There are numerous other examples of government policies which conflict with the efforts to reduce petrochemical inputs (10, 11). Technical Constraints. The dynamic nature of IPM systems requires a perpetual research and extension effort for farm level programs to succeed in each and every growing season. One of the biggest technical constraints to ongoing IPM implementation has been the fickle nature of public funding for research and extension of IPM on the farm. It is not clear where the



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future leadership for this funding will emerge or whether or not the critical momentum of past IPM research and extension programs can be maintained (13). Our firm was the dubious beneficiary of the entropy that occurs when extension efforts towards IPM implementation cease. During the 1970's, California pear growers were the recipients of a joint USDA/University of California research and extension IPM implementation project. This effort led to the publication of the nation's first comprehensive IPM field manual (14). One of the contributors and early implementors of this program was the U.C. Cooperative Extension agent in the Suisun Valley growing district. When he retired in the early 1980's, there was a dearth of IPM information from the extension office serving the area. A few growers had, during this period, retained our firm to provide commercial IPM advisory services. This was a particularly difficult economic period for Suisun Valley pear growers as manifested in orchard abandonments and area-wide reductions in cultural inputs including sprays for codling moth. As the 1985 pear harvest began, it became clear to growers that codling moth damage was exceeding economic levels. Virtually, the entire pear crop from the 4000 acres in the district was rejected by the canneries. In short, when IPM information ceased from the extension service, growers ceased monitoring for codling moth and received little information regarding orchard pest control. Consequently, most growers did not react to the then annually increasing moth populations. The result was an economic disaster for most of the district's pear growers. The exception to the above was our clients. During this period of dwindling inputs, our codling moth monitoring program indicated to us that our clients needed to increase their efforts at controlling this pest. In 1985, on the basis of our monitoring information, we strongly recommended that our clients apply an additional spray to suppress codling moth. Though our clients resisted this additional expense, the fact that they were among the few who had marketable crops that year proved the value of the added effort. Because our clients were so visibly successful in 1985, the next season found us in a much expanded cooperative role with the district's pear industry, the agricultural commissioner and the extension service. Since 1985, we have been conducting an areawide codling moth monitoring and IPM advisory program for all of the members of the local fruit growers' marketing cooperative. To regain control of codling moth required three seasons of heavy applications of pesticides and the elimination of abandoned orchards. Crop protection in general and IPM specifically does not occur in a vacuum! In addition to ongoing research into IPM strategies and tactics, to implement IPM at the farm level requires the development of site specific information (monitoring). Once that information is developed it must be interpreted and adequately communicated to the grower—decision maker. This requires an orientation and technical expertise that is in rare supply in



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most agricultural communities. Even where interest in IPM exists, farm advisors are often taxed for time and resources to implement IPM in depth to all their constituents. It is unreasonable to expectfieldpersons,employed by farm chemical suppliers, to be motivated or oriented towards the use of non-chemical crop protection alternatives. Indeed, they may often be reluctant to or incapable of conducting the intensive level of monitoring required to implement IPM alternatives. Thus, private consultants and "inhouse" pest managers should provide the best potential source of front line IPM implementation. However, their numbers are relatively few and there are very few programs to train and encourage this sector. Therefore, it is questionable as to who will actually provide the farmer with the information and experience necessary to conduct technically complex IPM at the farm level. We currently lack the personnel to implement IPM or any other technological alternative to synthetic pesticides. Any IPM funding program must take into consideration the need to perpetuate the IPM program at the farm level (72). The lack of aggressive development of pest specific pesticides, "biorational" pesticides, practical pest monitoring techniques, economic and action thresholds, computer software and other viable alternatives to unilateral reliance on pesticides are additional technical constraints to successful implementation of IPM. Current trends within the land grant universities, which de-emphasize applied agricultural research, further erode the potential to mitigate the above technical constraints. Summary and Conclusions. Integrated Pest Management is again being touted as an alternative to unilateral reliance on chemicals for crop protection. As such, IPM has the potential to mitigate many of the problems associated with pesticide use, including concerns related to food safety. Indeed where IPM programs are utilized, overall reductions in pesticide use have been demonstrated. Apples and pears are being produced free of detectable pesticide residues in California due, at least in part, to IPM efficiencies. However, there is little public, political, regulatory, producer, processor, retailer, consumer or environmentalist understanding of the complexity that IPM and its proper on-site implementation represents. Consequently, resources are simplistically directed towards limiting pesticide technology rather than utilizing the technology appropriately as a component of the broader, biologically based crop protection system known as IPM. A metaphorical comparison of the state of modern crop protection and plant health with modern medicine illustrates the problems faced by participants in the food safety debate. If medicine today were in the equivalent predicament found in the plant health industry, there would be ever increasing legislative and regulatory pressure to restrict and/or eliminate the pharmaceutical drugs used to prevent and cure disease. When disease organisms became resistant to an antibiotic, there would be few, if any, viable alternative medications. There would be little in the way of professional training, education and certification programs for physicians. Pharma-



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ceutical salespersons and pharmacists would be the dominant source of medical diagnoses and prescriptions for drugs. There would be few competent physicians to conduct delicate surgical procedures. This, unfortunately, is the condition in agriculture today. Pesticides are being severely restricted or eliminated. Commercialization of new, potentially safer pesticides is meager. Many key pests are rapidly developing resistance to the fewer remaining chemicals. TTiere is no agricultural equivalent to the American Medical Association. There are no formal programs to train plant health practitioners leading to the equivalent of an M.D. or D.D.S professional degree. Regulatory sanctions allow pesticide salespersons to prescribe the use of the petrochemical products which are the basis for their incomes. Indeed, the majority of licensed pest control advisors (PCA's) writing pesticide recommendations in California are employed by farm chemical suppliers. Few plant health practitioners, regardless of affiliation, are trained in alternatives to petrochemical inputs. Most critically, there is little awareness from any sector of the need to rectify or even debate these conditions. IPM currently has the ability to reduce pesticide residues in food. Indeed, many of the growers who are utilizing IPM intensively have been producing products free of detectable residues. With pears and apples we are capable of producing these fruits and bringing them to market with no detectable pesticide residues but are we "pesticide free"? We still must use pesticides and will continue to need pesticides into the foreseeable future. To accomplish goals of food safety perhaps we must first define the term. Is it possible that food is not totally safe and that we need to understand better whichriskswe are willing to accept? During 1979 for example, in El Dorado County, California, organic apple juice was condemned by the County's health department due to high concentrations of patulin mycotoxin. This extremely hazardous poison is produced by pénicillium mold which enters fruit infested by codling moth. As codling moth is usually the single most damaging pest of organic apples, the potential for patulin is high where, as is common practice, wormy fruit is pressed for juice. There are numerous other examples of naturally occurring plant toxins, rots, etc. Should de minimus standards be set for residue testing if the "no detectable residue" concept is desired by producers and retailers as a marketing tool? Should more efforts be directed, not to extermination of pesticide technology but towards utilizing that technology in an appropriate manner to ensure the benefits while minimizing the risks? Perhaps the delivery of pesticide technology should be reviewed as a means of determining whether or not the problems associated with pesticide use are inherent to the technology or a function of how that technology has been delivered to and used by the agricultural end user. The issue of food safety is complex but not insoluble. Production agriculture in the U.S. will continue to provide safe products if American farmers can maintain market competitiveness. To that end, IPM offers the single best system for ensuring an abundance of high quality, inexpensive, diverse and safe, often pesticide residue free food.


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Literature Cited

1. Metcalf, R. L.; Luckman, W. Introduction to Insect Pest Management; Wiley: New York, 1975; Chapter 1. 2. Metcalf, R. L. Ann. Rev. Entom. 1980, 25, 241. 3. Lacewell, R. D.; Masud, S. M. Economic and Environmental Implications of IPM; Frisbie, R. E.; Adkisson, P. L., Eds.; Integrated Pest Management of Major Agricultural Systems, 1985. 4. Regulating Chemicals: A Public Policy Quandary; Univ. of Calif. Ag. Issues Center, 1988. 5. Residues in Fresh Produce—1988; Calif. Dept. Food and Agric., 1989. 6. The Invisible Diet; California State Assembly Office of Research, 1988; p 26 7. Weddle, P. W. Proc. 32nd Ann. Conf. Int. Dwarf Fruit Tree Assn. 1989, 22, 130-33. 8. Weddle, P. W. Field Investigations Comparing the Effects of "Hard" and "Soft" Pesticides on Arthropods, Yields and Cosmetic Qualities of Bart Pears in the Sacramento Valley; Calif. Tree Fruit Agreement, 1989. 9. Dover, M.; Croft, B. Getting Tough: Public Policy and the Management of Pesticide Resistance; World Resources Institute, 1984; pp 18, 31, 34. 10. Alternative Agriculture; National Research Council, 1989; pp 10-13, 219. 11. Chemicals in the Human Food Chain: Sources, Options and Public Pol icy; Carter, H. O.; Nuckton, C. F., Eds.; Univ. of Calif. Ag. Issues Center, 1988. 12. Pesticide Resistance: Strategies and Tactics for Management; National Research Council, 1986; p 29. 13. Whalon, M. E.; Weddle, P. W. Implementing IPM Strategies and Tactics in Apple: An evaluation of the Impact of CIPM on Apple IPM; Frisbie, R. E.; Adkisson, P. L., Eds.; Integrated Pest Management on Major Agricultural Systems, 1985. 14. Pear Pest Management; Bethell, R. S.; Davis, C. S., Eds.; Univ. of Calif. Press, 1978. RECEIVED

August 19, 1990


Pesticide Residues and Food Safety - ACS Publications - American

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