Bugs and basil: Insecticides and veggies don't always mix

Who wants to eat insecticide?  Not me, and I'm guessing certainly not your customers.

So if your company does residential pest control, are your employees trained to know what to do when they encounter a vegetable garden, fruit or nut tree in a backyard?  And are they trained to answer a customer's questions about the safety of their insecticides around vegetables or herbs?  

Do your employees know what to do when encountering vegetables, herbs 
or other food plants around a home? Asking a customer about their edible
plants might save that account. Photo by Jeff Raska. 

I'm guessing this subject is not commonly addressed in technician training classes. I was asked by an industry sales representative this week: "Is it appropriate for a technician to be recommending that a homeowner simply wash their vegetables after having their yard treated for mosquitoes, or should the vegetables should be thrown away?"

The answer to this question depends on whether the plants were directly exposed to the spray and what the label says.

I did a quick review of the common mosquito adulticides used in backpack sprayers.  None of them allow application to edible plants.  The Suspend® Polyzone label, for example, says “do not apply this product to edible crops.” The Fendona® label says to not use on vegetable gardens.  Some make no mention of vegetables or edible crops at all.  And when it comes to edible plants, if application is not explicitly mentioned, it's not allowed.

Will pesticides make a plant toxic?

Of course many insecticides, including some of the active ingredients in your tool kit, are used legally on crops all the time by farmers. This is allowed by the EPA only if that pesticide has been granted a tolerance for a given crop, and certain days-to-harvest intervals are followed.  These rules work to ensure that any pesticide residues left after a pesticide application are below levels of concern for human health. The 2016 Pesticide Data Program survey by USDA shows that this system works. Out of 10,000 market food samples analyzed in the study, over 99 percent had residues well below the EPA established tolerances. More than 23 percent had no detectable pesticide residue.

So insecticide residues on plants are not necessarily toxic, especially when label directions are followed and adequate time passes to allow the product to naturally degrade. The products we use in pest control may be the same active ingredients used by farmers; but they may differ in concentration and formulation. Most importantly, pest control insecticides do not carry food-treatment labels so they cannot legally be used on edible crops.

Talstar® products, for example, consist of the active ingredient bifenthrin, the same active ingredient used by farmers and even home gardeners under a variety of trade names. The Talstar® P label for mosquito control, however, says "not to apply to bearing fruit or nut trees or vegetables or edible crops." To a law judge it won't matter whether other formulations allow application to food crops. To a judge enforcing FIFRA requirements, you must follow the label on the product you are using.

Spray contamination 

If an insecticide is deliberately sprayed on an edible crop or plant, and the product is not labeled for such use, the plant would not considered safe by EPA standards. The implication is that all of the plant, or at least the edible parts, should be thrown away. Your customer could replant, of course, unless prohibited by the label.

Backpack mistblowers are commonly used
for applying residual insecticides to mosquito
resting sites; but mists should be applied carefully
to avoid drift onto fruit and nut trees and
vegetable gardens.

Labels generally do not, however, prohibit use of these products in the vicinity of a vegetable garden. I assume this means that if you take care to keep sprays directed away from vegetable gardens, any incidental drift from nearby spraying with a coarse spray, aerosol or mist generator equipment should not be a problem. Likewise, thermal foggers and ULV applications used nearby should leave insignificant residues as long as the application orifices are directed away from edible plants at all times.

Of course applicators should always be aware of weather conditions and the locations of edible plants.  If wind is blowing toward a garden, upwind applications should be avoided.

So what should you do if a fruit, nut, vegetable or herb is is accidentally over-sprayed? Such a plant should be pulled, or else the produce should be left uneaten or discarded, by the customer.

Systemic insecticides

Some insecticides are "systemic," meaning they have enough water solubility to be taken up by plant roots and translocated to other parts of the plant. Although the EPA allows some systemic insecticides on crops, in general systemics are not labeled for use on food crops because they can leave residues in edible plant tissues that do not quickly degrade.

Insecticides containing neonicotinoids and acephate are examples of PMP insecticides that may be systemic in plants. These include products like Merit®, Premise®, Transport®, Tandem®, Alpine®, Temprid®, Orthene® and others.  Herbs and other root or leafy vegetables exposed to systemic insecticides should be considered contaminated for the season and should not be consumed.

Some termiticides can also be systemic in plants, leading to concerns about vegetable gardens planted next to homes treated for termites. Fipronil, for example, is slightly systemic in some plants; and the Termidor® SC label says not to "apply around edible plants."  The label does not say explicitly how far away an edible plant must be, although the Premise® 2 label (whose active ingredient, imidacloprid, is much more water soluble) is more specific. It says to "not treat within a distance of one foot out from the drip line of edible plants."  The Premise® guideline, therefore, is probably a good, conservative guidelines for all termiticides. Keep the outermost leaves of garden plants at least a foot away from any soil-applied termiticide and you should be OK.

Washing

Regarding washing, your technician may want to suggest vegetable washing to a concerned customer whose nearby yard or house perimeter has been treated with an insecticide spray.  Washing is a good idea whether pesticides have been used or not. The best washing technique includes a pre-rinse with a 10% vinegar solution (for germ control) followed by 30 seconds of tap water.  This is a great way to remove urban dust, microorganisms and traces of pesticides from vegetable and fruit surfaces.  

Would you recognize an edible plant?

Lastly, can you and your technicians tell a basil from a begonia, a mint from a marigold, or a pear from a poplar? Any applicator wanting to follow label directions around a home needs to be aware of what plants are present. We all don't have to be botanists, or know all the local tree species; but we should recognize the most common fruit and nut trees, herbs, and vegetables. Would you know what the common herbs sage, basil or rosemary look like? Sounds like a good exercise for training day.

When visiting a residence the first time, ask your customer if they have any herbs, fruit trees, nut trees or vegetables that you need to be aware of. Today's gardeners are more likely to plant edible plants within flower gardens, so you might have a basil plant or a tomato plant growing among the daisies. Assume your customers are organic in their vegetable garden and avoid these areas accordingly.

Believe me, your customers will appreciate any extra consideration you give to their home gardens. Treat them well and they might even greet you at the door with a big bag of zucchini.

Cedar oil or Snake oil? Control claims disputed.

Manufacturers who claim to control insects
affecting human health, like this head louse,
must be properly registered and have data
 that shows efficacy against the target pest.

The company claimed that their bed bug and head lice insecticide was invented by the U.S. Army, and acknowledged by the USDA as the number one choice of "bio-based" pesticides. The company also claimed that the U.S. EPA was warning consumers to avoid "chemical solutions" for treating bed bugs. The problem was that the company's claims weren't true.

As a result of false claims and illegal marketing of untested products for bed bugs and head lice, yesterday the Federal Trade Commission issued a judgment and settlement with a Texas-based manufacturer of cedar oil based insecticides. This action was a follow-up to charges filed last fall against another manufacturer of an unproven bed bug treatment containing cedar, cinnamon, lemon grass, peppermint and clove oils.

So what's so bad about making dubious insect control  claims for a supposedly "safe" product like cedar oil? After all, the U.S. EPA has frequently let the market determine which products really are effective against many pests.  And if the product really is "safe", what's the harm of promoting it and letting consumers figure out whether it works or not? We know that cedar oil does have effectiveness against some pests, like many other essential oils.

Historically regulators have drawn a line in the sand, and rightly so, for products that claim to control bed bugs, mosquitoes, head lice or other pests affecting human health. If you think you are protecting your or your children's health by using a product, the federal government has long taken the stance that you have a right to be reasonably sure that the product should work as advertised.

While the FTC cautions consumers about advertisements that offer quick solutions to bed bug infestations, this is a problem that affects professionals as well. Even professionals are prone to be duped by false or overblown marketing claims.  Consider this: if it were easy to control bed bugs with a do-it-yourself product why would people continue to need your professional services?  And look around.  Are your competitors finding bed bug control easy? There is still no "silver bullet" for bed bugs.

What's missing from many marketing claims is scientific research involving replication and untreated controls. And it makes sense that a company selling a product for such uses should be able to produce research results that justify their sales claims. So if you're considering investing in a new bed bug insecticide for your home or business, here are some questions to ask:

• Is the product registered with the U.S. EPA as a bed bug (or head louse or mosquito, etc.) insecticide?  
• If a manufacturer claims their product to be exempt from EPA registration, is the company also making claims that their product protects humans from pests that can harm human health?  If so, they may not be qualified to be exempted from label requirements. For the rules concerning exempt pesticides, and a list of active ingredients that really are exempt under the 25(b) provision of FIFRA, go to http://www.epa.gov/oppbppd1/biopesticides/regtools/25b_list.htm 
• What is the toxicology profile of the product?  Just because a product is natural doesn't mean it's safe. Ask to see the Safety Data Sheet and find out whether the product has been tested by the EPA.
• Can the manufacture produce data from an unbiased testing laboratory to show the efficacy of their product?  Do the data include comparisons with untreated controls, and were tests replicated and shown to be statistically significant?
• Does this data show that both susceptible and pesticide-resistant strains are killed?  This is especially important for bed bugs.  I've seen some products tested only against bed bug strains that are known to be highly susceptible to most insecticides (e.g., the bed bug 'Harlan strain'). Such products may not perform as well against tough field strains that your technicians are most likely to encounter.
• Does the product have to be sprayed directly on the pest, or is there data to show that exposure to dried residues will also kill the pest?  If residual testing was conducted, how long was the pest exposed to the residue?  Is this exposure time realistic for the bed bug populations you are treating?
• Does the data show that the product kills eggs as well as nymphs and adults?  Again, this is especially important for bed bugs.
• How well does the product perform compared to other standard pesticides being used for the pest?

And if your customer asks you about why they need your services when they can buy "Kilz Em Safe" online or at the local garden store, it might pay to point them to the FTC's warning against products that promise a quick solution.  Remind them that when they hire you, they're paying for more than insecticide.  Every good pesticide applicator knows that it's not just a natural insecticide that will get the job done safely.  It's the knowledge of where and how to safely apply a good insecticide that's important.

Risks and pesticides

I was reading a new product label this morning and came across a phrase that caught my attention. The label stated that "It is impossible to eliminate all risks inherentlyassociated with the use of this product."

This phrase, undoubtedly drafted by a lawyer and--I suspect--ignored by most users of the product, reminded me of a profound principles of pesticide toxicology and safety testing--one that I think few of us fully understand or appreciate: "It's impossible to prove that a pesticide is absolutely safe."

Science is a wonderful process. It allows us to discover useful things about our world. It forms the basis for new technology, answers our deepest questions about the universe, and brings wonder into our lives. Science, however, has it's limits. One of its limits is that it cannot prove absence of harm with complete certainty. It's the old "you can't prove a negative" argument.

Let me give an example. If my job is to test the safety of a new pesticide, I may expose a variety of organisms to my product to see if anything bad happens. Toxicologists routinely do this in laboratories with mice and rats and bacteria. Some tests are designed to measure acute toxicity, others look for evidence of mutations, others for cancer or other chronic disease. Suppose in the course of my testing all the rats develop cancer. This would be alarming evidence that my pesticide might be a human carcinogen. Evidence is strengthened if there are epidemiological studies that show a pattern of elevated cancer rates in humans exposed to the pesticide during its manufacture or use.

Now suppose there are no signs of cancer or other illness in my animals. Have I proved that my pesticide is safe? No. Science, because of physical and economic limitations, cannot prove safety with absolute certainty. For example, pesticide toxicology studies are not generally performed on people for ethical reasons. And people, despite our many occasional similarities, are not rats. Also, we cannot rule out all possible genetic, environmental or health factors that might influence carcinogenicity.

We know of cases, for example, where pesticides have proved exceptionally toxic to people taking certain prescription drugs. In these cases the drugs interfered with the user's ability to detoxify the pesticides, making them more toxic.

If we insisted that science provide absolute proof of safety, the science would become almost infinitely expensive. The best we can do is require a robust set of testing requirements, and base our decisions on the best available science. In addition, there should be a system of reporting suspicious patterns of health complaints associated with pesticide manufacture and use.

This is exactly what we do in the United States. The U.S. has, arguably, one of the best pesticide registration and approval processes in the world. New pesticides are incredibly expensive to register, in large part because of the safety testing required by the U.S. Environmental Protection Agency. The biggest beneficiaries of this regulatory process are those of us who work with pesticides on a daily basis.

So what's a pesticide applicator to do? Follow the label. The answer is so obvious that we often forget to do it. Labels are written to provide wise protection from the admitted limitations of our science when it comes to safety testing. From the precautionary statements, to the requirements for protective clothing, pesticide labels provide uncertainty protection.

Though they can be extremely uncomfortable in heat (especially in our part of the country), gloves, respirators and chemical resistant clothing, when required on the label, are essential to our safety. It may be necessary to explain this to a customer who balks at an applicator wearing gloves or breathing filters. They can be told that the extra protection is required by law (the label is the law) because, unlike them, applicators are exposed on a daily basis to our pesticide tools. It's not an admission of toxicity; it's a common sense precaution. It's an acknowledgement that we don't take unecessary chances with ours or our customer's health.

We should remember that there will always be risks working with pesticides, as with nearly any other consumer chemical product. That's the surprisingly wise message of the pesticide label.