Cooperative Extension Service
The University of Georgia College of Agricultural and Environmental Sciences

Your source for pest management and pesticide news

August 2005/Volume 28, No. 8


Do not make the cure worse than the problem when faced with fall webworm

HEALTH AND THE ENVIRONMENT

As if their poop was not bad enough, birds may also transport pesticides
You may not use the word “enantiomer” at cocktail parties (unless you have imbibed too much), but it is important in pesticide discussions
According to an article published in Ecological Applications (8-05), Roundup Grass and Weed Killer herbicide killed 98 percent of the tadpoles in a three-week test simulation of shallow ponds

BIOTECHNOLOGY

Articles published by the National Academy of Sciences and Nature magazine report that no genetically modified (GM) corn was found in Mexico
Scientists in China have introduced a scorpion gene and a gene from tobacco hornworm into canola

FQPA

According to the EPA’s newly released schedule, reregistration eligibility decisions (RED) and interim RED should be complete for all pesticide food uses by August 3, 2006
The EPA has released the RED for 2,4-D
The EPA has released the preliminary risk assessment
for the N-methyl carbamate pesticides.

DON’T DO IT

On March 8, 2005, Alfred Craft of West Monroe, Louisiana, pled guilty to violations of the Federal Bald Eagle Act and the Migratory Bird Act
The EPA is seeking more than $700,000 in penalties from a company in New York, charging that the company was not protecting workers from pesticide exposure

 

Do not make the cure worse than the problem when faced with fall webworm. At this time of year, calls about fall webworm are common. The extensive webbing enclosing the ends of one or more branches is obvious and unsightly. The typical control response seems to resonate from the primordial urge to set fire to anything that will burn. At the risk of insulting the Neanderthals and pyromaniacs, control of webworm is usually unnecessary, and fire is almost always a risky choice for insect pest management.

In most situations, fall webworm will not cause significant damage to trees. It is near the end of the season, and leaves have nearly served their useful life for the tree. Even extensive defoliation will not harm most trees. Webworms have numerous natural enemies, so an uncontrolled infestation this season does not necessarily mean a worse problem next year.

However, the ragged nests are unattractive, and many people would prefer to eliminate them from the home landscape. A number of control options are readily available. The environmentally friendly Bacillus thuringiensis will kill fall webworm caterpillars with little or no risk to birds, bees, and other non-target animals. Several products (e.g., Dipel and Thuricide) contain this active ingredient. For best results, buy fresh product and apply it when the webworm larvae are small. Most other chemical insecticides will also provide control; products containing pyrethroid active ingredients (e.g., permethrin or cyhalothrin) are effective against caterpillars.

For some people, fire is an appealing control option. Admittedly, it is more exciting than applying an insecticide, but the risks outweigh the perceived benefits. Fire is unpredictable, and the risks to human health are obvious. It also pollutes the environment. Gasoline, kerosene, diesel fuel, etc. are all environmental pollutants, highly toxic, and human carcinogens. Fire is almost certainly going to injure the tree, while the webworms are only a marginal threat. Finally, fire will eliminate many of the organisms that provide natural control of webworm populations.

Here is a picture of the adult. They don’t have an interesting common name, just adult webworm. This website will give you more information. http://www.bugwood.org/factsheets/webworm.html

Health and the Environment

As if their poop was not bad enough, birds may also transport pesticides. Many types of birds range over large areas, yet join in large, compact colonies during certain times of the year. As the birds forage, they may accumulate pesticides or other pollutants. When the birds form colonies, their deposits may become quite large over time. Substantial amounts of pollutants may build up around colonies, particularly if the birds return to the same area year after year.

Fulmars are medium-sized seabirds; northern fulmars form an annual colony of about 10,000 pairs on an island in the Arctic. Scientists found that the birds’ guano was responsible for a 60-fold increase in concentrations of DDT (and breakdown products) in nearby ponds and a ten-fold increase in the pesticide hexachlorobenzene When birds forage at sea, they pick up mercury and pesticide residues, which end up accumulating near nesting colonies, suggests a study in Arctic Canada. (Science News, 7-16-05)

You may not use the word “enantiomer” at cocktail parties (unless you have imbibed too much), but it is important in pesticide discussions. About 25 percent of pesticide molecules occur in two forms, identical in composition and mirror images in structure. Your hands or a pair of gloves are good examples. For pesticides that occur as enantiomers, one form may be more toxic or more persistent than the other. Most pesticides are sold as mixtures of the two variants. With more information about the difference between the enantiomers, scientists could design better pesticides.

In some recent experiments, the biological activity was dramatically different between the two variants of a pesticide. For some pyrethroids, one enantiomer was 38 times more toxic than the other. Essentially, only one form of the pesticide molecule was responsible for nearly all of the pesticidal activity. In related experiments, scientists found that one form of a pesticide may degrade much slower than its mirror image. (Science News, 1-8-05)

The EPA has posted a database with information about what happens to pesticides in the environment. The database includes information about the physical and chemical properties of the pesticide. You will also find information about the chemicals left over when the pesticide breaks down. In some cases, the degradates are as dangerous as the original pesticide.

Some of the important information about pesticides in the current database include:

  1. basic physical and chemical properties,
  2. biotic and abiotic degradation half-lives in soil and water,
  3. adsorption/desorption constants, and
  4. bioconcentration factors in fish.

For non-agricultural chemicals such as antifoulants and wood preservatives, the availability of the chemicals in water and leaching data are also included.

You will find the database here http://cfpub.epa.gov/pfate/index.cfm.

According to an article published in Ecological Applications (8-05), Roundup Grass and Weed Killer herbicide killed 98 percent of the tadpoles in a three-week test simulation of shallow ponds. In another experiment, the herbicide killed 79 percent of the young frogs and toads in one day. The registrant, Monsanto, responded that this experiment used an unrealistically high rate of Roundup and that the results were contradictory to some other, similar experiments.

The newspaper account (St.Louis Post Dispatch, 8-7-05) reported that the toxic agent is a surfactant present in the product and not the active ingredient (glyphosate). The article adds that a Monsanto glyphosate product (Biactive) sold in Australia and Europe contains a different surfactant and is much less harmful to amphibians. Monsanto says that the surfactant would be less effective against North American weeds and would have to pass through a cumbersome approval process.

Follow these links for more information. Both of the links go to the same story for now, but newspaper links often change quickly.

http://www.insnet.org/ins_headlines.rxml?cust=2&id=1401&url=http://www.ledger-enquirer.com/mld/ledgerenquirer/news/nation/12330342.htm

http://www.stltoday.com/stltoday/news/stories.nsf/sciencemedicine/story/B7940508F57E80F986257057004F4808?OpenDocument&highlight=2%2C%22roundup%22

Monsanto Comments on Ecological Applications Paper Concerning Amphibians and Roundup Brand Herbicide Formulation http://www.monsanto.co.uk/news/ukshowlib.phtml?uid=8800

It can be difficult to separate the wheat from the chaff in these kinds of stories. On one hand, Roundup did kill a large proportion of the tadpoles and frogs. However, Monsanto points out that the rate used in the experiments was three to seven times higher than an ordinary application. They added that North American labels for Roundup do not permit application to water. Maybe it is no surprise that an illegal application of Roundup at exaggerated rates kills tadpoles.

We should not rush to judgment or regulatory action based on these data. However, the EPA should obtain more information. The worldwide decline in amphibians is troubling, and some scientists think that amphibians may be the metaphorical canary in the mine.

Biotechnology

Articles published by the National Academy of Sciences and Nature magazine report that no genetically modified (GM) corn was found in Mexico. Modified corn was of particular concern in Mexico because the ancient lines of maize are maintained there; scientists were concerned about accidental contamination of the historical corn lines with genes that had been added to modern varieties. Maintaining the purity of the ancient maize varieties could be important if we need to add some trait (e.g., disease resistance) to a modern variety. The government imposed a six-year moratorium on GM corn, but it was found in Mexico a few years later.

After testing more than 150,000 seeds, scientists concluded that any transgenes that had been present had been reduced to undetectable levels. The drop was attributed to farmer education and the reduction of GM imports. You will find more information at the world’s longest URL:
http://www.pnas.org/cgi/content/abstract/102/35/12338?maxtoshow=&HITS=10&hits=10&RESULTFORMAT=&fulltext=mexico+maize&searchid=1126296046910_6803&stored_search=&FIRSTINDEX=0&journalcode=pnas

Scientists in China have introduced a scorpion gene and a gene from tobacco hornworm into canola. The scorpion gene encodes for a protein that affects an insect’s nervous system. The gene from the hornworm produces a chemical that breaks down chitin, which is essential for the insect exoskeleton. Scientists hope that the combination will slow the development of insect resistance to the proteins. You can read more details here. http://pest.ifas.ufl.edu/CMSP-2005/08cmsp05%20files/08cmsp05-L05.htm (Thanks to Chemically Speaking, 8-05)

Most people do not seem overly excited about foods with genes from other plants. I wonder if people will feel the same way about eating food containing a scorpion protein. Eventually, we will face some religious concerns as well. Suppose a gene from a pig is used in soybean. Would any product made with the soybean oil be taboo for Muslims and Jews?

Did you hear scientists inserted a gene from a collie into pit bulls? They will still chew your leg off, but then they go for help.

FQPA

According to the EPA’s newly released schedule, reregistration eligibility decisions (RED) and interim RED should be complete for all pesticide food uses by August 3, 2006. For all non-food uses subject to reregistration, the process should be complete by October 3, 2008. You will find the schedule at http://www.epa.gov/pesticides/reregistration/candidates.htm.

At times, regulatory activity may be hot and heavy to meet the 2006 deadline. Watch for opportunities to submit information about pesticides important to your industry. The Agency has reiterated their commitment to public input on pesticide decisions. This web site (http://www.epa.gov/oppsrrd1/publicsched.htm) provides a schedule of the pesticides in the review queue and the open comment periods. The table is updated every six months. Some of the high profile chemicals scheduled for the rest of 2005 include acetachlor, amitraz, malathion, pyrethrins, and soil fumigants.

The EPA has released the RED for 2,4-D.For those of you who have been sealed in a cave, 2,4-D is a widely used herbicide; it kills broadleaf plants but not grasses. It has many agricultural and non-agricultural uses. With certain restrictions, all 2,4-D uses are eligible for reregistration. The agency and the registrants have agreed to the following risk reduction measures.

Because of concerns about human carcinogenicity, 2,4-D has been in pre-Special Review for nearly 20 years. In 1992, EPA said that there were insufficient data to classify 2,4-D relative to human carcinogenicity. The agency reaffirmed this decision in 1999. More recently, the EPA reviewed epidemiological studies linking 2,4-D to cancer and concluded that none of the more recent studies definitively link human cancer cases to 2,4-D. A Special Review will not be initiated. Some people would criticize EPA for taking nearly 20 years to decide if 2,4-D was a carcinogen, but it is difficult to find data that clearly define the link between a particular chemical and cancer. That uncertainty is why we remind people to minimize their exposure to all pesticides. The truth is that we still do not know for sure if 2,4-D can cause cancer.

The 2,4-D RED, risk assessments, and other related documents are available on EPA’s 2,4-D reregistration Web site, http://www.epa.gov/oppsrrd1/reregistration/24d/.

The EPA has released the preliminary risk assessment for the N-methyl carbamate pesticides. This group includes carbaryl (Sevin), aldicarb (Temik), methomyl (Lannate), carbofuran (Furadan), and other less familiar pesticides. This group is being considered together because all of the N-methyl carbamate insecticides interfere with acetyl-cholinesterase. Because thiocarbamate and dithiocarbamate pesticides have little activity against acetyl-cholinesterase, they are not included in this risk assessment; examples include maneb, mancozeb, and metam sodium. (8-19-05 EPA OPP Update)

A brief, simplified refresher for the scores of students who fell asleep during my pesticide lectures (some of you may feel drowsy even now). In both humans and insects, the nerves and muscles communicate with a chemical called acetylcholine. The muscle contracts when it receives this chemical from a nerve. The muscle will continue to contract repeatedly as long as acetylcholine is present or the muscle fails. Acetyl-cholinesterase breaks the acetylcholine into acetic acid and choline. In humans, the process takes about 80 microseconds (microsecond = one millionth of a second).

All of the N-methyl carbamates interfere with the activity of acetyl-cholinesterase, and FQPA requires EPA to group pesticides with a similar toxic mode of action. The EPA used a similar process when they estimated the cumulative risks of the organophosphates.

The carbamate assessment is based on an evaluation of the potential for people to be exposed to more than one member of this group of pesticides at a time, and considers exposure from food, drinking water, and residential sources. EPA considers the results to be preliminary; therefore, it is too soon to draw firm conclusions about risks or consider risk management possibilities. The Agency cautions against premature conclusions based on this preliminary assessment and against any use of information contained in these documents out of their full context.

You will find more information at these websites.

For information on assessing cumulative pesticide risk, visit http://www.epa.gov/pesticides/cumulative/. The preliminary risk assessment is available at http://docket.epa.gov/edkpub/do/EDKStaffCollectionDetailView?objectId=0b0007d4807f42bb.

The review process for the N-carbamates will follow the pattern established with the organophosphate insecticides. People complained about some parts of the organophosphate exercise, and we should be alert to guard against similar problems. Some of the more common complaints are summarized here.

  1. It seemed like the peach registration for methyl parathion was summarily canceled. Methyl parathion was the most widely used peach insecticide in the Southeast, and peach growers did not feel they had much opportunity for input. Some people thought that the Agency and the registrant “cut a deal” in response to public and political pressure. Ironically, another organophosphate insecticide replaced methyl parathion in most orchards.
  2. Except for malathion, organophosphate insecticides are not available for use in and around homes. These wholesale cancellations were primarily driven by the potential for children to be exposed to organophosphates around the home. Some people thought that the evidence of harm to children was weak and that EPA removed valuable pest management tools with little reduction in risk.

Applicators that need N-carbamates need to be involved in the process from the beginning. The EPA needs information to make science-based decisions, and Agency scientists want data. However, the EPA often acts under strict time deadlines, and they may be forced to make a decision with minimal data. We should collect data about N-carbamates now and be ready to submit the information quickly.

Although the agency is performing a cumulative assessment for the N-carbamates, some of the chemicals are greater risk than others. Some carbaryl registrations may be at risk because this chemical has a large number of food-use and household registrations. The registration for carbofuran has been in jeopardy for some time. It is highly toxic to birds and considered a threat to groundwater. Illegal residues of aldicarb have been reported in potatoes and bananas, and aldicarb has been implicated in animal poisonings.

Applicators have created unnecessary pressure for carbofuran and aldicarb. People regularly use both chemicals to kill birds, dogs, cats, and other unwanted animals. Additionally, many applicators think nothing of giving the chemicals to a friend or neighbor. Every reported incident of an animal being killed with aldicarb or carbofuran pushes these valuable tools nearer to cancellation. NEVER use pesticides illegally; NEVER give pesticides away unless you know the applicator will use them responsibly.

Don’t Do It

On March 8, 2005, Alfred Craft of West Monroe, Louisiana, pled guilty to violations of the Federal Bald Eagle Act and the Migratory Bird Act. He killed the birds when he baited predators on his property with meat laced with aldicarb. To compound his troubles, Mr. Craft was also convicted of threatening two witnesses.

This case may have other losers as well. The person who supplied Mr. Craft with aldicarb could face liability. This incident pushes aldicarb that much closer to the cliff of cancellation. Ironically, many growers will grouse at EPA if the aldicarb registration is cancelled. Based on its history of repeated misuse, some people are surprised that aldicarb was not cancelled long ago.

The EPA is seeking more than $700,000 in penalties from a company in New York, charging that the company was not protecting workers from pesticide exposure. New York State fined the same company $1,000,000 for insufficient training of applicators and other violations. http://www.dec.state.ny.us/website/press/pressrel/2001/2001x95.html

Unless you have an extra million dollars, develop a written training program for your pesticide applicators. Follow pesticide label directions to the letter.

The appearance of any trade name in this newsletter is not intended to endorse that product nor convey negative implications of unmentioned products.

Dear Readers:

The Georgia Pest Management Newsletter is a monthly journal for extension agents, extension specialists, and others interested in pest management news. It provides information on legislation, regulations, and other issues affecting pest management in Georgia.

Do not regard the information in this newsletter as pest management recommendations. Consult the Georgia Pest Management Handbook, other extension publications, or appropriate specialists for this information.

Your input in this newsletter is encouraged.

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Department of Entomology
University of Georgia
Athens, GA 30602

E-mail: bugman@uga.edu

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http://pubs.caes.uga.edu/caespubs/entomology/pestnewsletter/newsarchive.html

Sincerely:

Dr. Paul Guillebeau, Associate Professor and Extension Entomologist