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A lovely irony is blooming. On one side groups are pushing for quick availability of safer, less-toxic chemistries to control pests, and on the other side groups are pushing for tighter regulation on products to prevent potential damage to humans and the environment. Can you guess the names of those groups? One side is represented by university scientists and state regulators, the other side is represented by consumers. But which group is on which side?
In
an August 24, 1999, article in USA Today, the battle lines were
neatly described. Consumers are voting with their pocketbooks
for what they believe are safer, less-toxic chemistries by supporting
Public Broadcasting Station (PBS) affiliates that carry Jerry
Baker, the self-described "America's Master Gardener."
Among other things, his advice to home gardeners is to use "tonics"
made from such things as chewing tobacco, human urine, birth control
pills, mouthwash, molasses, detergent, and beer. What are his
qualifications for dispensing such advice? He has television presence
and he is a "superstar" on PBS fundraising drives. Never
mind that he is not part of the university Cooperative-Extension-based
Master Gardener programs, which have dispensed science-based information
since their inception in 1971.
Is Baker a problem, from a scientific perspective? Scientists in Ohio thought so, when they petitioned their local PBS station in Columbus to remove Baker's show, citing examples of improper and illegal recommendations for pesticide use given by Baker during the shows. Their complaints were rebuffed by the station.
Some interesting examples of Baker's recommendations given
in the USA Today article included frequent shampooing of lawns
and plants to improve photosynthesis and the inclusion of a tablespoon
of bourbon with a plant fertilizer. These recommendations fall
into the "snake oil" category: they likely won't hurt
the plants, but the benefits are dubious. (Unless perhaps you
give the plant the fertilizer and you take the tablespoon of bourbon
yourself. At least you might feel better about the plant afterward.)
Other examples of Baker's recommendations are not so funny. To
kill bugs, use a chewing-tobacco-and-water mixture. To kill suckers
growing on trees, Baker recommends using "any good weed killer"
with dish soap, vinegar, and gin. After pruning flowering trees,
Baker recommends sealing the wounds with latex paint, antiseptic
mouthwash, and an insecticide such as Sevin or Dursban. What's
wrong with those three recommendations? (1) Nicotine is a lethal
human poison; (2) Roundup (a "good weed killer") can
severely damage trees; (3) using Sevin around blooming plants
is an extremely irresponsible action that leads to bee kills,
exactly the type of environmental damage that consumers profess
to abhor. 
Everyone has heard stereotypical comments about academics, from the stuffy "ivory tower mentality" to the more impertinent "egghead." While Baker was not quoted using any of those comments, he did say "the redwood trees grew just fine before we had garden centers and people with academic certificates. I can't worry about what the competition says." It should be news to scientists and regulators that they are "the competition" for consumers' attention and welfare. Odds are that scientists and regulators believe they are working for the consumer, primarily toward guaranteeing that marketplace products are safe to humans and the environment when used as stated, that those products consistently meet stated efficacy claims, and that each lists its active ingredients on the label.
Is Jerry "Master Gardener" Baker the only perpetrator of egregious recommendations? Of course not. Should we "egghead" academics in our "ivory towers" be concerned? I think so.
The marketplace is full of labels classified as "minimum risk;" as such, they require no Environmental Protection Agency (EPA) registration number and are loosely called 25(b) products. (See Federal Register of March 6, 1996, 61 FR 9976.) University scientists and state regulators are concerned that labels are in the market with illegal ingredient statements, few or no guidelines for the use of personnel protective equipment, and no assurance that the product has had even a cursory efficacy review before entering the marketplace. These labels give the consumer the impression that the product is non-toxic, encouraging by default unnecessary human and environmental exposure. Indeed, concern is high enough among these scientists and regulators that they have drafted a letter to EPA through the American Association of Pesticide Safety Educators, requesting that the 25(b) regulations be revisited with an eye toward tightening them.
Consumers are usually the first to demand tighter regulations to protect the unwary from being bilked by snake oil salesmen. They are often the first to demand greater protection of humans and the environment from unnecessary pesticide exposure. But that seems only to be the case when the bugs are in someone else's backyard.
Dr. Catherine Daniels is the Pesticide Coordinator at WSU's
Pesticide Information Center. Despite her ivory tower location,
she can be reached relatively easily at (509) 372-7495 or cdaniels@tricity.wsu.edu
.
Have you ever wondered what goes on behind the scenes in the process of publishing a pesticide usage recommendation?
When one homeowner chats with another over the backyard fence about which fertilizer she is using on her tomatoes, that's one kind of recommendation: a casual, personal recommendation. When you represent an institution of higher learning with a responsibility to the public, there is no such thing as a "casual" recommendation. For our purposes, a "recommendation" is a mention of the use of a particular agent in a particular way on a particular crop or site. By making a statement of this nature, we are vouching that the described use is
Here at Washington State University (WSU), when a new or revised publication containing references to pesticides goes through our Publications Department or Cooperative Extension, these offices pass it along to the Pesticide Information Center (PIC) with a sign-off form. This applies to web pages as well as printed documents.
PIC staff reviews each publication for appropriate language, technical correctness (with respect to pesticides), and label conformance. We are particularly concerned with human health language (e.g., in matters concerning worker safety) and with environmental protection language (e.g., in matters concerning waste disposal, spray drift warnings, etc.) When appropriate, we consult Carol Ramsay (WSU's Pesticide Education Program coordinator) and/or members of Washington State Department of Agriculture's Registration and Compliance branches on wording.
Our office then checks the document for label conformance. We verify the crop or site, product trade name, active ingredient, package type (commercial vs. homeowner), rates, pests, timing, numbers and methods of application, pre-harvest intervals (PHIs), and re-entry intervals (REIs), matching up each recommendation with one or more federal and/or state-registered, labeled products. We make sure the registrations are current. In short, we ensure that every statement in the document about using a particular product is checked against a label. The only exceptions are those allowed under federal and Washington State law; if the document says to use less product than the labeled rate, if the document says to use the product less frequently than the label states, or if the document recommends product use on a pest not listed on the label, we do not instigate a change.
If our research fails to locate a label verifying the statements made in the publication, we call the author(s) and discuss the situation. If they are able to identify a label we missed, we obtain the label, verify it, and proceed with document approval. If no corroborating label is found, we ask the author(s) to modify the document so that any recommendations conform to a current label.
How does this review process benefit the author? One advantage to authors is legal protection. WSU is self-insured. If an author follows the review process and is sued, that author will be covered under WSU's insurance. If not...well, they're on their own.
The WSU administration feels that the PIC review function is important, and we continue to seek ways to improve it. Over the last eight years, we have begun keeping a record of our publication reviews as well as a record of the data used in approving or changing each publication submitted to us. This record includes the Environmental Protection Agency registration number, the company that registered the product, and the trade name of the label used in our verification process.
We were curious about how other states deal with recommendations and reviews. In an effort to better understand, we distributed a survey to our counterparts in Alaska, Arizona, California, Colorado, Guam, Hawaii, Idaho, Montana, Nebraska, Nevada, New Mexico, Oregon, Utah, and Wyoming. Of the fifteen contacted, eleven responded.
Each institution provides materials to the public, which may include extension bulletins, fact sheets, manuals, handbooks, videos, and/or newsletters. Approximately half the states (AK, AZ, HI, UT, WY) plus Guam have no university policy or state law defining what constitutes a "pesticide recommendation;" the others (CA, ID, MT, NE, NV) define "pesticide recommendation" similarly to WSU: as a crop/chemical statement with use directions.
Four states (HI, ID, UT, WY) require no review process for publications containing pesticide references produced by their institution. Of those remaining, the periodic reviews required are conducted by peers (AZ, Guam, MT, NE, NV), the Pesticide Coordinator (CA, WA), or the Pesticide Applicator Training coordinator (AK). Most states treat home and garden product references in the same fashion as commercial references. A few (AK, CA, WA) go beyond legally mandated criteria when making homeowner-use recommendations, considering variables such as lack of personal protective equipment and waste-stream concerns when dealing with homeowners.
All U.S. state respondents have Master Gardener programs (Guam does not), and most Master Gardeners recommend pesticides when appropriate. Over half of these (AK, HI, MT, NE, UT, WY) have no policy as to limitations of Master Gardener recommendations, where others have specific limitations, deferring to university specialists or published guidelines.
All states and territories share a common concern for public safety. Due to Washington State law, we lean toward the conservative side when making recommendations, with substantial deference to regulations and policies designed with public health and safety in mind. Regardless of state or institutional regulations, university extension specialists throughout our survey regions consider the same factors when making recommendations:
Dr. Catherine Daniels is the Pesticide Coordinator for WSU;
Sally O'Neal Coates is an Editor of Research Publications. Either
can be reached at WSU's Pesticide Information Center, (509) 372-7492,
or individually via e-mail at cdaniels@tricity.wsu.edu
or scoates@tricity.wsu.edu.
|
"My cup runneth over" is a well-worn adage used to express good fortune or bounty, but in the language of today's regulatory world a full cup spells trouble for those who use pesticides. At least if that cup is a "risk cup."
The risk cup is the Environmental Protection Agency's (EPA's) conceptual approach to estimating total pesticide exposure and risk. EPA believes that about 80% of a typical U.S. citizen's pesticide intake occurs through food, and that the remaining 20% comes from drinking water and residential exposures. These fractions clearly differ from compound to compound, but for the organophosphate (OP) pesticides, this accurately characterizes EPA's current picture of the risk cup.
The Food Quality Protection Act
(FQPA) of 1996 requires EPA to make sure that all exposure pathways
are taken into account (a concept called "aggregate exposure"),
and states that food tolerances must be reduced if the risk cup
is too full. FQPA also charges EPA to determine the total or "cumulative
risk" posed by the groups of pesticides with common mechanisms
of action. Early on, EPA identified the OP pesticides as the first
group to undergo this analysis. The specifics of how to calculate
aggregate exposure and cumulative risk are still being debated
hotly, but most everyone involved in pesticide regulation agrees
that the OPs are vulnerable. It was no surprise, therefore, when
in August EPA Administrator Carol Browner announced new restrictions
on the use of methyl parathion and azinphos-methyl across the
United States. Both are ranked in EPA's highest toxicity category
(Toxicity I) due to acute toxicity concerns. Phosdrin and ethyl
parathion, two other OP pesticides lost to agricultural use in
recent years, fall in the same category. Each of these compounds
attacks the nervous system of insects and humans alike, inhibiting
cholinesterase, an essential enzyme.
Once upon a time we called these acutely toxic chemicals "economic poisons." This phrase may sound like an oxymoron in 1999, but in the earlier part of this century it was a practical term used commonly by entomologists and other scientists to describe chemicals that killed insects in agricultural production. Everyone who uses the more toxic OP pesticides today knows that they are inherently hazardous, and takes special care while handling them. Ingestion of OP pesticides remains one of the most common means of suicide in the world.
The first serious efforts to measure worker exposure to pesticides were prompted in large part by the introduction of OP pesticides into orchards of Washington State. The U.S. Public Health Service opened a laboratory in Wentachee in the early 1950s and began to document skin contact and absorption as a possible explanation for poisoning incidents that had previously been a mystery. Their work led to many of today's recommendations and requirements for pesticide applicator protection.
But why did Carol Browner point the finger at methyl parathion and azinphos-methyl? Do we really need further restrictions of OP pesticides? Maybe these are the wrong questions. If the question is, how do we best protect the health of the public, then EPA's recent action makes much more sense.
The EPA Administrator is obligated by law to reduce the total risk posed by OP pesticides across the United States. Congress set a stringent timeline for action. Her job is to make sure that the "risk cup" is never full for anyone, or at least not for 99.9% of the population (0.1% represents roughly 300,000 people). The simplest way to reduce total risk is to restrict use of the most toxic OP compounds. Thus, Toxicity I chemicals are the most likely targets for regulation, while Toxicity II compounds such as phosmet, malathion, and chlorpyrifos are likely to remain in use.
The acutely toxic OP pesticides remain a hazard in the workplace. Workers who handle these chemicals are required to wear protective suits, gloves, boots, and respirators at all times, and field workers are prohibited from entering treated fields for several days after application. The Bayer Corporation recently extended the restricted entry interval for azinphos-methyl to fourteen days in apples, presumably to reduce risks among agricultural reentry workers. The margin of error for working with some of these chemicals can be slim, as we learned with phosdrin use earlier in this decade. While the safety record for worker poisonings has improved here in the Northwest over the years, the use of Toxicity I chemicals will always require vigilance, and can never be considered risk-free.
EPA is bound by a pledge to Congress in 1993 to reduce significantly the amount of pesticides used in the United States. EPA was joined in this commitment by the U.S. Department of Agriculture and the Food and Drug Administration. One result has been EPA's Pesticide Environmental Stewardship Program, which actively promotes integrated pest management (IPM). This emphasis on overall pesticide use reduction is part of a global trend. The Organization for Economic Cooperation and Development (OECD) has initiated a Pesticide Risk Reduction Project in partnership with the World Health Organization's Food and Agriculture Organization (FAO). And the European Commission is about to release the results of a 6-year study of pesticide use, along with recommendations for new strategies to reduce pesticide risks. These strategies will likely include reduced use of some pesticides. Thus, EPA's new restrictions should be viewed as part of an ongoing process among regulatory agencies in many countries to phase out some of the older pesticides, while encouraging new product development and alternative pest management approaches.
Unlike the media reports in the days of Alar, most coverage of the new EPA restrictions stressed the safety of the nation's food supply. Reporters seem to have learned a lesson about creating unwarranted fears among consumers with alarmist messages. But it is also important to remember that these new restrictions are not really comparable to the Alar controversy at all. This is not just about apples, and the OP pesticides are nothing like Alar. (Alar is not acutely toxic, but was of concern because its breakdown product, UDMH, caused cancer in test animals.) Both methyl parathion and azinphos-methyl are used on a wide variety of fruit and vegetable crops. Prior to the new restrictions, approximately six million pounds of these chemicals were applied annually in the United States. The new restrictions are designed to eliminate some high-risk uses completely, but will allow many other uses to continue with modifications. In the case of apples, where the use of azinphos-methyl is deemed critical, producers are still allowed to apply nine pounds per acre, down from twelve pounds per acre. EPA's willingness to be flexible in developing these new restrictions shows a new sensitivity to the economic consequences of regulations.
The EPA has often been criticized for its regulatory decisions related to pesticides, and at times with good cause. In some past cases the logic behind the decisions has not always been apparent, but EPA's current procedures are characterized by a new openness and clarity. In the spring of 1998 EPA and the U.S. Department of Agriculture were called upon to create a public process that would allow all interested parties access to the science and reasoning used in decision making. Pesticide manufacturers and agricultural industry representatives have been permitted to scrutinize the smallest details of the process, and they have hired numerous scientific experts to assist them with this task. Risk assessments for methyl parathion and azinphos-methyl have been posted on the EPA website for review, and each step that EPA has taken has been debated in public settings. While disagreements may remain about specific procedures or interpretations, the process has clearly been thoughtful, and was conducted in plain view.
What is the future for other OP pesticides in light of EPA's obligation to reduce risks for consumers and workers? The creative efforts of many scientists are now focused on finding alternative pest control methods. As mentioned earlier, Washington State's apple growing regions were the site for many initial discoveries about OPs and health risks in the 1950s, and it appears that Washington may once again take a pioneering role by identifying innovative and practical pest control solutions. Washington State University recently received funding from the state legislature for twenty new faculty positions to support the state's new Safe Food Initiative. This initiative calls for increased research in biological control of pests in an effort to move away from dependence on chemicals. In public health, the central focus of research and education is prevention. Pesticide use reduction is one important way to reduce risk for workers and consumers alike. Ideally, USDA and EPA will work together to make pesticide use reduction practical and manageable for all concerned.
Dr. Richard Fenske is Professor of Environmental Health
at the University of Washington's School of Public Health and
Community Medicine, and Director of the Pacific Northwest Agricultural
Safety and Health Center (PNASH). He also serves on EPA's Science
Review Board, a congressionally mandated advisory board for pesticide
science policy. He can be reached at rfenske@u.washington.edu
or (206) 616-1958.
According to the New York Times, in an article dated August 20, 1999 (http://www.nytimes.com/library/tech/99/08/biztech/articles/20farm.html), farmers are using the Internet in record-breaking numbers. Citing a recent study by the National Agricultural Statistics Service, the article claimed that the percentage of agricultural producers connected to the World Wide Web more than doubled, from 13% to 29%, between 1997 and 1999. How and why do farmers use the 'Net?
Here in the Northwest, percentages are higher than the national average. Washington, reporting 50% Internet access, ranks second in the nation (NewJersey reports 53%), while Idaho reports 41% and Oregon, 29%. We are sure the vast majority of these savvy ag surfers are logging onto http://picol.cahe.wsu.edu regularly to check the Pesticide Information Center On-Line (PICOL) database and other fascinating and useful information gathered and reported by the PIC. Thanks to Tony Wright of Washington State University's College of Agriculture and Home Economics for bringing this news clip to our attention and to Terence Day for assisting with interpretation of data. See Day's related news release from the WSU College of Agriculture and Home Economics at http://cahenews.wsu.edu/releases/99084.htm, along with links to other on-line resources.
The endangered or threatened status of specific salmon populations could force the federal government to impose stiff regulations on land and water use in the Pacific Northwest. These imposed regulations, spawned from the Endangered Species Act, could impact land use on nearly seventy-five percent of Washington State. Additional regulations, precipitating from the Clean Water Act, could impact over 660 streams. Washington State forest product and agricultural industries sit squarely in the bull's-eye of increased regulation and hunting season could open any day now. Proactively, the Washington State Farm Bureau has pledged support for Governor Gary Locke's 1999 plan to promote the recovery of salmon populations (Johnson 1999). This plan calls for the establishment of riparian buffer zones and imposes limits on activities along streams. Which rivers and streams are chosen, how wide buffer zones must be, and which plants can be used in the buffer zones will affect future land use across Washington State.
Insects will likelyprosper in buffer zones, so we can expect a migration of both pest and beneficial arthropods from buffer zones into surrounding agricultural fields. Which pest or beneficial insects arise from buffer zones will depend largely on which plant species persist in the buffer zones.
In Governor Locke's salmon recovery plan, riparian buffers will consist of outer and inner zones. The plan recognizes obvious differences in rainfall, vegetation, and land-use patterns between eastern and western Washington. In the agricultural regions of eastern Washington, the inner zone (i.e., zone closest to the water) will be either 75 feet (if the stream width is 15 feet or less) or 100 feet (if the stream or river width is greater than 15 feet).
The outer zone extends from the outside boundary of the inner zone a distance equivalent to the height of "the site potential tree." Sagebrush being the dominant "tree" in most eastside agricultural areas, the outer zone is negligible on agricultural lands.
The bottom line is that buffer zone size is rather specific to the plot of land affected. The Do The Math sidebar below shows a sample calculation.
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Example calculation of buffer zone* size for an eastern Washington stream over 15 feet wide.
5280 feet in a mile 43,560 square feet in an acre) |
Proposed streambank mitigation strategies promote the use of "native" plant species in riparian buffer zones. However, specific plant species are rarely suggested. Fortunately, my colleague Dr. Bob Stevens at Washington State University's (WSU's) Irrigated Agriculture Research and Extension Center (IAREC) was able to provide me with contacts to develop a list of twenty-eight plant species currently recommended for use in riparian habitats (Table 1).
In natural ecosystems, plants generally persist in a state of relative homeostasis, i.e., in balance with their environment. Herbivores and diseases are prevalent but complex associations among the ecosystem's many inhabitants maintain community stability. These associations include interlocking food webs, extensive food partitioning, and co-evolution among plant, herbivore, carnivore, parasite, and pathogen (Walsh 1999). I doubt that a 200-foot riparian buffer zone strip winding though agricultural fields will achieve homeostasis.
Armed with a working list of twenty-eight plant types or species, I was able to review the literature and consult several WSU experts for associated arthropod, weed, and viral pests. Tables 2, 3, and 4 list pests that might pose a risk to crops if any of the recommended native plant species occur in the managed buffer zones.
Many insect pests use native plants as alternate hosts. For example, the pollen produced by willows is nutritious to a variety of pest moths and beetles and snowberry is an alternative host for apple maggots.
Virulence of plant viruses can vary; in fact, most are innocuous in nature. However, some viruses are damaging. Often viruses are vectored from plant to plant by insects.
The Random House dictionary defines a weed as "a valueless, troublesome, or noxious plant growing wild, especially one that grows profusely to the exclusion or injury of the desired crop." Most damaging weeds in Washington State are of old-world origin. Freed from the herbivores and diseases of their native habitats, these plants spread rapidly and many have gained habitat dominance in the Pacific Northwest. It is unlikely that "native" plants will persist and out-compete naturalized weed species in buffer zones.
Go back to Arthropod Pests
text
Just east of Prosser, near IAREC, the Benton County Conservation District has rehabilitated a stream bank with perennial bunchgrasses. My fellow entomologist Ron Wight and I visited the site on September 16, 1999. The stream bank looked beautiful, with bunchgrasses filling most of the bank within about twenty-five feet of the five-foot-wide stream. However, interspersed near the stream bank and increasing in prevalence to become the dominant plant was the fairly recently introduced (about twenty years ago) exotic weed species Kochia scoparia L.
We sampled the insect fauna using a sweep net. The dominant insect species present was Lygus hesperus Knight. Lygus bugs are a native insect pest that have readily shifted to many crop plants as they have been introduced. Biological control strategies against Lygus have for the most part failed, in my opinion. Buffer zones could potentially become reservoirs for generalist pests like Lygus.
The good news is that our sweep net samples also contained many generalist insect predators. These beneficial insects included several species of coccinelids (i.e., Ladybird beetles), hemipterans (damsel, big-eyed bugs, and minute pirate bugs), neuropterans (brown lacewings), and dipterans (syrphid flower flies). We also observed several species of braconid and ichneumonid parisitoid wasps.
Large areas of untreated land adjacent to an agricultural field should enhance the survival of beneficial predatory or parasitic arthropods. Another potential beneficial side effect of riparian zones is the presence of untreated refuges that allow survival of pesticide-susceptible pest insects. These insects could breed with potentially pesticide-resistant insects and help keep pest populations susceptible.
Mosquito larvae develop as juveniles in aquatic habitats. The Benton County Mosquito Abatement District reports that the dominant mosquito species in Eastern Washington is Culex tarsalis Coquillet, referred to as "treehole mosquitoes." Their larvae develop in small stagnant bodies of water. Correspondingly, Culex mosquito populations will not be reduced by a greater abundance of healthy and hungry fish in clean running waters. Additionally, adult mosquitoes require nourishment from a sugar source. Typically this is acquired from nectar from a floral or extra-floral source. Mosquitoes also require shelter from the elements and predators. Riparian habitats provide both food and shelter for mosquitoes. Recent research from rice-growing regions in California has demonstrated that riparian habitats contain the greatest abundance of adult female (i.e. biting) Culex mosquitoes (Wakesa 1996). A broad increase in acreage devoted to riparian habitats could lead to greater populations of Culex mosquitoes. Culex is the primary vector of western equine encephalomyelitis and St. Louis encephalitis (Reeves et al. 1994).
The Governor's salmon recovery plan states, "The use of pesticides will be managed to meet water quality standards and label requirements and to avoid harm to riparian vegetation." With few exceptions, pesticide application will be prohibited in buffer zones. Specific exemptions are targeted towards satisfying local noxious weed control issues. Exceptions for agricultural or public health arthropod pests are not mentioned.
How the imposition of long, narrow tracts of land planted in native and naturalized weedy plant species will effect beneficial and pest arthropod abundance is yet to be determined. From experience, I think it will lead to greater populations of Lygus bug and other generalist pests. However, I believe that it will lead to greater populations of beneficial arthropods as well. The waters are muddy (pun intended), but I have no doubt that it will certainly prove to be a challenging and interesting time to study entomology.
Dr. Douglas B. Walsh is an Agrichemical and Environmental Education Specialist with WSU's Food and Environmental Quality Laboratory. He can be reached at dwalsh@tricity.wsu.edu or (509) 786-2226.
Contributions of information from WSU professors Bob Parker (weeds), Keith Pike (insects), and Ken Eastwell (pathogens) were invaluable in synthesizing the information for this essay. |
"Conventional agriculture must be replaced with sustainable
agriculture." How many times have you heard such statements
uttered by politicians and policy makers who talk about sustainability
as if it were an immediately available off-the-rack technology?
Such a myopic perspective doesn't consider that today's seemingly
sustainable practices may not be functional as tomorrow's technology.
Technology constantly evolves as we experiment by trial and error to discover how sustenance can be provided without messing up our own nest. Long before every technology and development policy was adorned with the imprimatur of "sustainable," agricultural scientists studied efficient and safe technologies for food production, knowing that soil and water quality was vital to crop production. Agricultural producers embrace these evolving technologies, known as best management practices, or BMPs, to meet societal expectations of cheap food and environmental stewardship.
During the past quarter century, the most-visible BMPs have been those developed to protect water resources from excessive contamination by eroded soil, fertilizer nutrients, and pesticide residues. BMPs for reducing agrochemical movement have focused on both the application process itself and the post-application losses. Historically, BMPs were developed mostly for in-field practices, either minimizing drift or reducing soil erosion and water runoff. More recently, the focus has shifted to include areas adjacent to and "downstream" of the field.
Buffer zones around agricultural lands have been proposed as effective "structures" for protecting adjacent sensitive aquatic and terrestrial habitats. Indeed, the Washington Farm Bureau strongly recommends that growers voluntarily develop buffer zones around or on their lands to protect streams with potential salmon-bearing habitat (Johnson 1999).
Buffer zones have value well beyond the protection of water quality and aquatic organisms. Buffer zone development can be a BMP for protecting sensitive nontarget crops or native plants. Our region grows a bewildering variety of crops in a mosaic pattern. The use of a herbicide in a tolerant crop growing in one field may be detrimental to a susceptible crop planted nearby. Conflicts between wheat and grape growers are legendary, as grapes are notoriously sensitive to the herbicide 2,4-D.
As suburban communities spread out onto former agricultural land, buffer zones can also help reduce conflicts between homeowners and growers due to noise, dust, odors, and pesticide drift.
The Commission on Agrochemicals and the Environment of the International Union of Pure and Applied Chemistry has recommended the following definition for buffer zone (Holland 1996): "Distance for environmental protection between the edge of an area where pesticide application is permitted and a sensitive non-target area, e.g., water course." By this definition, the buffer zone starts at the edge of the last swath of pesticide spray, but does not necessarily include only land outside of the growing crop. A grower could make the decision to not treat several outside rows of his crop, effectively allowing his cropland to be part of a buffer.
Depending on what one is trying to protect, buffer zones could be temporary or permanent spaces. If one was trying to avoid damaging an adjacent sensitive crop during application, leaving some unsprayed rows might suffice, but other agricultural practices (for example, soil management practices) would not be restricted. If reduction of the effects of water runoff or erosion is the objective, a buffer zone around a field would essentially need to be permanent as agrochemical runoff can occur long after application.
There has not been sufficient research reported to determine
the relationship between the size of a buffer zone and its effectiveness
in controlling runoff and erosion. Available research has tended
to focus on types of plants that might be best for either absorbing
excessive nutrients at the edge of a field or for filtering out
sediment during a rainstorm.
Buffer
zone size has usually been studied in relation to management of
spray drift. Choosing a buffer zone size is easy when size is
mandated by regulation. For example, the Forest Practice Rules
in Washington prohibit any spraying within fifty feet of a riparian
management zone (RMZ). RMZs are natural landforms consisting of
vegetation (grasses, bushes, trees) lying adjacent to rivers and
streams, whether ephemeral or permanent. While RMZs potentially
reduce spray drift, they are not necessarily going to stop runoff,
especially when streams meander through a treated area. Whether
fifty feet is adequate to stop spray drift into streams was questioned
several years ago by the Washington Department of Ecology and
resulted in a proposal to increase the length by nearly fivefold
(Rashin and
Graber 1993).
Obviously, there is no one-size-fits-all answer for how big a buffer zone should be to effectively reduce the impact of spray drift. What is needed is a strategic plan that can customize the buffer zone for a particular situation. Such a strategic plan incorporates four elements: physical laws of particle movement, nature of the habitat outside the treated area, toxicological responses of the organisms to be protected, and a graphical synthesis of the first three elements.
The objective of a buffer zone, whether permanent or temporary, is to eliminate adverse effects outside of a field or forest plantation. Given the fundamental physical laws of chemical movement, buffer zones developed for pesticide management are unlikely to completely eliminate residues outside the treated field. However, buffer zones can effectively reduce exposure of sensitive organisms by taking advantage of fundamental laws of physics. What goes up, must come down. And the heavier something is, the sooner it must fall.
Regardless of what pesticide is used, spraying creates tiny droplets (particles) that are pushed around by air currents. The heavier, bigger particles fall to the ground very quickly and never leave the field. The lightest, smallest particles move great distances, but become less concentrated (i.e., more dispersed) the longer they stay airborne and thus, less likely to cause harm when they eventually fall to the ground. Of more concern are the particles adequately sized to move just beyond the field boundary and fall on bodies of water, sensitive crops, or someone's house. The buffer zone must be big enough so that when the particles come down, there are not enough of them to adversely affect anything beyond the buffer zone.
Because spray drift is controlled primarily by particle sizes emanating from the nozzles and secondarily by factors like wind and sprayer type, mathematical models can simulate many spray scenarios. One such model, AgDRIFT, has been constructed by the agricultural chemical industry in cooperation with the Environmental Protection Agency (EPA) (Teske 1997). The output of this model can be graphed as the relationship between the amount of a spray that drifts and distance to deposition (Figure 1).
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The concentration of the spray particles that fall just outside
the buffer zone will depend on structures within the buffer zone.
For example, hedges and trees can intercept spray droplets, effectively
reducing their numbers before they exit the buffer zone. If water
is to be protected, the nature of the water body is a factor.
For example, a fixed number of spray particles falling in moving,
deep water will result in less pesticide concentration than the
same number falling on stagnant, shallow water. The resulting
concentration in the receiving waters is important because "dose
makes the poison." Or as one skeptic I know put it, "dilution
is the solution to pollution."
The third factor needed to design an adequately protective buffer zone is knowledge of what pesticides can be used and the sensitivity of the organisms that need to be protected. The identity of the pesticides and any nearby sensitive crops or residential neighborhoods can be easily determined. More difficult to predict are the myriad of aquatic organisms in an adjacent stream.
The most conservative strategy, which is favored by the EPA for ecological risk assessments, is to use the response of the most sensitive organism in short-term (four days or less) toxicity tests. These tests provide the acute LC50, or the concentration of a substance in water that kills 50% of the organisms. For protection of humans, the strategy is to find the lowest dose, commonly called the no observable effect level (NOEL), not causing any type of adverse effect in 90-day feeding tests with rats, mice, or dogs.
Once these toxicity benchmarks are determined, they can be further divided by a safety factor, resulting in a level of exposure that is reasonably certain to be without harm. For humans, the resulting tolerable dose is called the acute reference dose (RfD), usually obtained by dividing the NOEL by 100. For aquatic organisms, the EPA uses a risk quotient approach. For example, for endangered species, the estimated environmental concentration must be at least twenty times less than the acute LC50 of the most sensitive test organism. The other possible benchmark for aquatic organisms is to use a statistically derived guideline (known as the ambient water quality criterion) that is based on numerous species tests.
At this point in the planning process, one has determined the spray drift potential, characterized the habitat needing protection, and determined the appropriate toxicological benchmark. The next step melds everything together to determine how far from the sprayed area a stream, sensitive crop, or person has to be before drifting particles are sufficiently dilute to cause no exposure beyond the safety guidelines. This distance defines the linear dimensions of the buffer zone.
Let's illustrate the process in a case study, using the herbicide 2,4-D as the subject. Say we want to protect a stream next to an irrigated wheat field. On the other side of the stream is a new housing development and a vineyard. The grower plans to hire a helicopter to spray the field with a formulation of 2,4-D at a rate of two pints per acre. A consultant is asked to determine what size buffer zone is needed to avoid the possibility of any harm to the adjacent nontarget areas. The consultant also determines how this buffer zone might differ if the 2,4-D was applied from a ground sprayer.
Using the AgDRIFT simulation model, we can predict how much
drift will occur at various distances downwind of the last spray
swath. The amount of drift depositing can be expressed either
as a percentage of the application rate or as an actual weight
of pesticide per unit of area (for example, milligrams of pesticide
per square meter, mg/m2). The relationship between pesticide deposition
and distance from the spray swath is graphically displayed as
a curve (Figure 1). The model does not account for vegetation
in the buffer zone that might intercept spray particles. Furthermore,
the model incorporates wind blowing at 10 miles per hour directly
toward the areas needing protection.
The RfD of 2,4-D for a 10-kilogram child is 0.1 milligrams per
day. This whole-body dose can be mathematically transformed to
a body surface area dose using EPA exposure parameters (EPA-ORD 1997) and assuming very conservatively
that a kid's entire body might be exposed to drift. For example,
a two- to three-year-old child has a total body surface area of
0.682 m2 (although, realistically, only the arms, legs, and head
would likely be exposed). Studies with humans exposed to 2,4-D
have shown that less than 10% of the dermal dose can penetrate
the outer skin. Thus, the "safe" dose can be multiplied
by a factor of ten because for every ten milligrams of 2,4-D that
falls on the skin, only one mg will actually enter the body. The
resulting toxicological benchmark expressed on a unit area basis
is 1.5 mg/m2 (Table 1).
For protection of aquatic organisms, the U.S. Geological Survey uses an ambient water quality criterion of 0.004 milligram per liter (mg/L, which is 4 parts per billion, ppb). If the stream were 1 meter (m) deep, then the benchmark concentration not to be exceeded would translate to 4 mg/m2.
No standard safety criteria have been developed for sensitive crops. However, one can often find a study in the literature that is applicable to the situation of concern. Fortunately, a number of herbicides have been tested with grapes to determine the lowest dose that can cause visible injury. A study at Washington State University showed that 2,4-D deposition below 1.1 mg/m2 should not harm wine grapes (Al Khatib et al. 1993).
Using the graph generated by AgDRIFT, the maximum buffer zone length can be determined by drawing a horizontal line from the deposition axis to the drift curve, and then dropping a perpendicular line to the distance axis. For example, a horizontal line drawn from the grape toxicity benchmark of 1.1 mg/m2 to the curve for ground and aerial spraying yields buffer zones of 40 and 335 feet, respectively (Figure 1, Table 1). A similar process is used to derive the buffer zones needed to adequately protect aquatic organisms and children (Table 1). A shorter buffer zone can be delineated for ground spraying because spray is released much closer to the ground from a tractor than from a helicopter; the spray particles tend to be bigger, so they deposit sooner.
The estimated buffer zones don't guarantee there will be no pesticide exposure. They only estimate, under worst-case conditions, the most conservative buffer zone lengths that could provide a reasonable certainty of no harm, which is how the Food Quality Protection Act (FQPA) defines safety. Whether buffer zones represent a BMP that will be considered sustainable years from now is indeterminate. BMPs are necessarily developed in the context of desired societal goals, and therefore are subject to modification. Based on what we know after many millions of dollars of pesticide testing, the germane question should be whether reasonable certainty of no harm is safe enough.
Dr. Allan Felsot is the Environmental Toxicologist with the Food and Environmental Quality Laboratory at WSU. He can be reached at afelsot@tricity.wsu.edu or (509) 372-7365.
Washington State University offers PRE-LICENSE courses (for those who do not have a license and need one) and RECERTIFICATION courses (for those who need to renew their current licenses). Fees are $35 per day if postmarked 14 days before the program, otherwise $50 per day. This fee DOES NOT include WSDA license test fee, which ranges from $25 to $170; for information on testing and fees, contact WSDA at (360) 902-2020 or http://www.wa.gov/agr/test/pmd/licensing/index.htm. Recertification courses offer 6 credits per day.
The Washington State Department of Agriculture (WSDA) currently maintains approximately 320 Special Local Need (SLN) registrations for over forty-five minor crops. SLNs are issued by states to address local pest problems when a federally registered pesticide is not available for the given use. About one-fifth of the SLN registrations in Washington are for organophosphate (OP) insecticides. Tolerance reviews for OPs, along with those for carbamates and B2 (potentially carcinogenic) chemicals, are among the top priorities for the U.S. Environmental Protection Agency (EPA) in the implementation of the 1996 Food Quality Protection Act (FQPA). With these chemistries under such scrutiny, Washington State growers are concerned about what pesticides will be available in the future.
This past summer EPA announced
regulatory changes for two OPs, methyl parathion and azinphos-methyl
(see related articles in AENews Issue 161, September 1999). These
actions should not have a great direct impact on SLNs, but a rapid
change from an OP-based program to an Integrated Pest Management
(IPM) program utilizing a wider range of other insecticides could
result in secondary pest outbreaks and the overall use of more
insecticides (Whalon et. al., 1999). Registrants are currently
required to cancel all methyl parathion SLNs, but may reapply
for new registrations for the specific uses that have been retained,
such as dried peas and lentils. EPA will conduct risk assessments
on more than thirty other OPs over the next year and a half, which
will likely lead to changes in other crop SLNs. Table 1 shows
review schedule for the thirteen OPs directly related to Washington
State SLNs.
It is thought that EPA will schedule risk evaluation for carbamates in late 2000. Meanwhile, EPA will review the human and environmental effects of older insecticides to ensure they meet current standards, possibly leading to further SLN changes. For example, the SLN registration for use of iprodione (Rovral) on crucifer seed crops will change due to the removal of application by air. EPA requested this revision to mitigate risk as outlined in the Reregistration Eligibility Decision (RED) document for iprodione. Electronic copies of REDs are available on the Internet (http://www.epa.gov/docs/oppsrrd1/REDs/index.html).
As chemical registrants decide which pesticide registrations to maintain, it is likely that minor crops will initially suffer the most losses (Evans, 1998), since there is little or no incentive to develop or maintain these uses (Bischoff, 1993). (Also see article, "IR-4: Developing and Delivering Solutions for Minor Crop Producers," in AENews Issue 162, October 1999.) In the case of apples, Washington's growers must now depend upon less effective and more expensive pest management systems due to the loss of methyl parathion and reduced use rates allowed for azinphos-methyl (Brunner 1999). Alteration of a tolerance during the reassessment process may affect 24(c) registrations by limiting the rate, timing, number, and/or method of pesticide applications. Elimination of tolerances would lead to a reduction in the number of SLNs.
The total number of SLN registrations issued has dropped by approximately eighteen percent during the past three years (based on 132 SLNs from 1994 through 1996 compared to 108 from 1997 through 1999). During the same periods, WSDA also issued a lower number of SLNs for food uses (81 from 1994 through 1996 compared to 63 from 1997 through 1999). While total SLN registrations are down, Washington has seen a surge in the number of SLNs issued for seed crops in the period from 1997 through 1999. Seed crop registrations accounted for about thirty percent of the total number in the last three years, compared to eighteen percent from 1994 through 1996.
Information on Pesticide Registration in Washington may be
obtained on the Internet at http://www.wa.gov/agr/.
If you have questions on WSDA pesticide registration procedures,
you can e-mail the WSDA Pesticide Registration Section at pestreg@agr.wa.gov, call
(360) 902-2030, or fax (360) 902-2093.
The proposed schedule for review of OPs can be found on the Internet at http://www.epa.gov/pesticides/op/actionops.htm and the priority list of carbamates and B2s scheduled to undergo EPA tolerance review is available at http://www.cast-science.org/fqp1_t1.htm.
Steve Foss is a Pesticide Information and Resource Specialist with Washington State Department of Agriculture. He can be reached at sfoss@agr.wa.gov or (360) 902-2049.
In the Pesticide Information Center (PIC), we spend a great deal of time reading pesticide labels. Then we translate that label information into computer codes and enter it as data. The end result of these efforts is the PICOL (Pesticide Information Center On-Line, pronounced "pickle") label database, accessed from the PICOL main page at http://picol.cahe.wsu.edu/.
For those of you who aren't familiar
with PICOL, the label database is a (free) searchable pesticide
database that tracks which pesticides are registered for use in
Oregon and Washington. The database is a veritable fount of knowledge
and can tell you, among other things, what products are labeled
for use on which crop and pest combinations. (Did I mention there
is no charge for using this database?) If you want to know the
active ingredient in a product or which products containing that
same active ingredient are registered for use, the database can
help (at no cost). Want to know what fungicides are labeled for
use on rhubarb? How about a list of imidacloprid-containing insecticides?
OK, you really want a list of herbicides labeled for use on kiwifruit,
registered by Dow, whose product names start with "Q."
The PICOL label database is the place to go.
Not only are all commercial-use pesticides tracked, the label
database also includes all homeowner products registered in Washington
and Oregon. So if what you really want is a list of disinfectants
claiming to be "fresh air" scented, the PICOL label
database can tell you that as well. (However, for a search this
odd, we just might have to charge you.) I cannot tell a lie: It
isn't always obvious how to get the database to give you what
you want. However, our nimble-brained staff is always ready, willing,
and (usually) able to walk you through a search. 
The main person responsible getting label information into the computer is our Database Coordinator, Ms. Charlee Parker. Charlee spends so much time focused on inputting label information that passersby have accused us of chaining her to her desk. (OK, now, before you get too worried, we do let her take an occasional break and once in a while, she even gets lunch.) Thanks to Charlee's diligent efforts, we are nearly current with data entry (no small feat!) and should have all 1999 registrations entered in the label database before the end of the year. (Note that even this late in the year we are still receiving Oregon and Washington 1999 registration information.) The other big plus to having Charlee on our staff is her attention to detail. She looks at everything very carefully and has even been known to spot the occasional error, enabling us to improve the existing database while adding volumes of current information.
In thinking about all of the time and effort we (this is the royal we of course) spend getting information into the label database, I couldn't help but wonder:
Luckily this soul searching has come to an end. Late last year, with help from the computer folks on our Pullman compus, we installed a log-in screen that requires all PICOL label/tolerance database users to provide us with some information about who they are and why they are accessing the system. This feature allows us to track database usage. (Some would argue that while we don't actually charge for use of the databases we do extract our fees via an annoyance factor.) Alas, there is no way to avoid this log-in step. Even the PIC staff must log in each time we want to access either of the label or tolerance databases.
The results are in but the news is mixed:
We have been tracking usage of the label database since the first of the year and tabulating our "hits" by location. As Table 1 shows, Washington residents comprise the majority of database users. We have done the requisite self-assessment: our office accounts for approximately 22% of the Washington hits (and 16% of total database access).
Because the label database provides information for a variety of uses, we also ask (read: "require") our users to tell us why they are accessing the system each time they log on. The customers have the option of selecting production agriculture, commercial applications in urban areas, homeowner-type application, or just browsing the system. Far and away, most of the label database users are inquiring about production agriculture, with the remainder split between the urbane urbans, banal browsers, and humble homeowners (see Table 2).
Whether you are looking for a "country fresh" disinfectant or a way to control green peach aphid in radish seed, come on, try out the PICOL label database. It's here. It's wow. (It's free.)
This article was prepared by Pesticide Notification Network
Coordinator Jane M. Thomas. For comments, questions, or a nimble-brained
assist with a database query, contact Jane at (509) 372-7493 or
jmthomas@tricity.wsu.edu.
|
In reviewing the September postings in the Federal Register, we found the following items that may be of interest to the readers of Agrichemical and Environmental News.
In the September 1 Federal Register, EPA announced that the revised risk assessments and related documents for ethoprop, fenamiphos, phorate, and terbufos were available for review and comment. These risk assessments can be accessed on the web at http://www.epa.gov/pesticides/op/status.htm. (Page 47784)
In the September 2 Federal Register, EPA announced that the preliminary human health risk assessments and related documents for coumaphos were available for review and comment. These documents are available on the web at http://www.epa.gov/pesticides/op/coumaphos.htm. (Page 48164)
In the September 17 Federal Register, EPA proposed establishing procedures for the registration of antimicrobial products, labeling standards for antimicrobial public health products (to ensure that these products are appropriately labeled for the level of antimicrobial activity they demonstrate), modifying its notification process for antimicrobial products, and exempting certain antimicrobial products from FIFRA regulation. The agency also proposes to interpret the applicability of the new FIFRA definition of "pesticide'' that excludes liquid chemical sterilants from FIFRA regulation and includes nitrogen stabilizers, and to describe requirements pertaining to use dilution labeling. Comments on these proposed actions may be submitted to EPA until November 16, 1999. (Page 50671)
The PNN is operated by WSU's Pesticide Information Center for the Washington State Commission on Pesticide Registration. The system is designed to distribute pesticide registration and label change information to groups representing Washington's pesticide users. PNN notifications are now available on our web page. To review those sent out in September either access the PNN page via the Pesticide Information Center On-Line (PICOL) Main Page on URL http://picol.cahe.wsu.edu/ or directly via URL http://www.tricity.wsu.edu/~mantone/pl-newpnn.html. We hope that this new electronic format will be useful. Please let us know what you think by submitting comments via e-mail to Jane Thomas at jmthomas@tricity.wsu.edu.
Chemical (type) |
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| cymoxanil (fungicide) | 9/1/99 page 47687 | 1 | dried hops | Yes | Extension | 10-15-01 |
| Comment: This time-limited tolerance is being extended in response to a request received by EPA to extend the use of cymoxanil for downey mildew control on hops for this year's growing season. | ||||||
| difenoconazole (fungicide) | 9/1/99 page 47680 | 0.1 | sweet corn (forage & stover) | Yes | New | 01-31-01 |
| 0.1 | sweet corn (kernel + corn with husk removed) | |||||
| Comment: This time-limited tolerance is being issued in response to EPA granting a Section 18 for the use of difenconazole on Idaho sweet corn seed. | ||||||
| avermectin B (insecticide) | 9/7/99 page 48548 | 0.02 | grapes | No | N/A | N/A |
| 0.02 | peppers | |||||
| 0.2 | dried hops | |||||
| 0.005 | potatoes | |||||
| 0.02 | cattle meat & mbp | |||||
| 0.005 | milk | |||||
| 0.1 | wet apple pomace | |||||
| sulfentrazone (herbicide) | 9/21/99 page 51060 | 0.1 | sunflowers | Yes | New | 12-30-00 |
| 0.1 | bean, succulent seed without pod (lima beans & cowpeas) | |||||
| Comment: These time-limited tolerances are being issued in response to EPA granting Section 18 exemptions for the use of sulfentrazone to control kochia in North Dakota sunflowers, and hop hornbeam copperleaf in lima beans and cowpeas grown in Tennessee. | ||||||
| tebuconazole (fungicide) | 9/22/99 page 51248 | 2 | barley grain | Yes | Extension | 12-31-00 |
| 20 | barley hay | |||||
| 20 | barley straw | |||||
| 15 | wheat hay | |||||
| 2 | wheat straw | |||||
| 0.1 | milk | |||||
| 0.2 | mbp of cattle, goats, hogs, horses, poultry, and sheep | |||||
| Comment: These time-limited tolerances are being extended in response to requests from various states for Section 18 exemptions for the use of tebuconazole on barley and wheat. | ||||||
|
spinosad (insecticide)
spinosad (insecticide) |
9/23/99 page 51451
9/23/99 page 51451 |
0.15 | wheat |
No
No |
N/A
N/A |
N/A
N/A |
| 0.3 | cucurbit vegetables | |||||
| 0.3 | edible podded legumes | |||||
| 0.2 | stone fruit | |||||
| 0.02 | corn grain (inc. field and pop) | |||||
| 1 | sorghum grain | |||||
| 0.02 | wheat grain | |||||
| 1 | cereal grain (forage, fodder, hay, stover, and straw) | |||||
| 20 | aspirated grain fractions | |||||
| 0.2 | poultry, fat | |||||
| 0.02 | poultry; meat, mbp, and eggs | |||||
| 0.02 | succulent shelled peas and bean legumes | |||||
| 0.02 | dried shell pea and bean (except soybean) legumes | |||||
| Note: This action also increases the following tolerances to the levels listed below. | ||||||
| spinosad (insecticide) | 9/23/99 page 51451 | 0.15 | meat of cattle, goats, hogs, horses and sheep | No | N/A | N/A |
| 1 | mbp of cattle, goats, hogs, horses, and sheep | |||||
| 3.5 | fat of cattle, goats, hogs, horses, and sheep | |||||
| 0.5 | milk, whole | |||||
| 5 | milk fat | |||||
| trifloxystrobin (fungicide) | 9/27/99 page 51901 | 0.5 | pome fruit | No | N/A | N/A |
| 0.5 | cucurbit vegetables | |||||
| 2 | grapes | |||||
| 5 | raisins | |||||
| 0.02 | wet apple pomace | |||||
| 0.02 | milk | |||||
| 0.05 | meat, fat, and mbp of cattle, goats, hogs, horses, and sheep | |||||
| diflubenzuron (insecticide) | 9/29/99 page 52450 | 0.5 | pears | Yea | New | 03-31-01 |
| Comment: This time-limited tolerance is being established in response to EPA granting a Section 18 exemption for the use of diflubenzuron to control pear psylla on pears grown in Oregon and Washington. | ||||||
| pymetrozine (insecticide) | 9/29/99 page 52438 | 0.02 | tuberous and corm vegetables (subgroup 1-C) | No | N/A | N/A |
| tebufenozide (insecticide) | 9/29/99 page 52457 | 0.3 | turnip roots | No | N/A | N/A |
| 9 | turnip tops | |||||
| 4 | canola, refined oil | |||||
| 2 | canola seed | |||||
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