Pesticides: Useful, Debatable and Banned

I gave a Zoom talk on Thursday, February 4th, 2021 to the Collier County Master Gardeners. The topic was controversial pesticides. The two pesticides we covered were Roundup and imidacloprid. But I only had one hour to hit the highlights. So, here are several references for your reading pleasure and comments.

Two years ago, a landscape maintenance worker in Naples was doing his usual spraying of Roundup in beds to kill weeds. A homeowner came running out and screamed at him “What are you doing!? Haven’t you heard that causes cancer? Don’t you know it’s banned?! Get that stuff out of here!”

The flustered worker retreated to his truck and called the company’s owner who called me and urged me to clarify the facts. Today’s talk is an expanded answer to that lady’s legitimate concerns.

Last year I prepared this presentation, but I had to cancel. Not because of Covid 19 but by cancer. Literally one year ago I had already undergone my second round of chemotherapy to treat Non-Hodgins lymphoma. After four more doses, I lost my hair and my energy but not my life. Thank God the chemo worked, and the cancer is gone. I kept a blog about my experience, If you or someone you know is going through cancer, this journal is encouraging.

When my doctor shocked me with a diagnosis of cancer, I urgently researched causes and cures. But where do you go for straight answers on this life-or-death topic? Facebook, Google, an attorney?

First I asked my oncologist. How did I get cancer? Are pesticides suspects? He set me straight and directed me to two solid sources of facts: The American Cancer Society and the Leukemia and Lymphoma Society. Those two sources lead me to numerous studies and peer-reviewed papers.

American Cancer Society

1:3 people will experience some form of cancer.

“at least 18% of all cancers diagnosed in the US are related to body fatness, physical inactivity, alcohol consumption, and/or poor nutrition, and thus could be prevented.”

List of known carcinogens:

Glyphosate does not appear their list.

Lymphoma and Leukemia Society. Lymphoma is a type of blood cancer. In U.S. there are 196,000 people with Hodgkin and 678,000 with non-Hodgkin lymphoma.

74,000 new cases each year. Typical is white male, age 80.

“The cause of lymphoma is not known.”

Risk factors: genetics, obesity, immune suppression, certain viruses and bacterium, and…

“Farming communities have a higher incidence of NHL, and farm work has been linked to major NHL subtypes and to NHL overall…

The number of lymphoma cases caused by exposures to herbicides and pesticides has not been determined. More studies are needed to understand these associations.

The risk factors identified for peripheral T-cell lymphomas include celiac disease, eczema, psoriasis, an extensive smoking history, and working with textiles or electrical equipment.”

“Glyphosate Use and Cancer Incidence in the Agricultural Health Study.” Conducted by the National Cancer Institute in May 2019. Forget about mice in labs. They studied pesticide applicators and the incidence of cancers. 54,251 people were included in this multi-year analysis.

“Conclusions: In this large, prospective cohort study, no association was apparent between glyphosate and any solid tumors or lymphoid malignancies overall, including NHL and its subtypes. “

To be fair, they added “There was some evidence of increased risk of AML among the highest exposed group that requires confirmation.” leads to the United States Department of Health and Human Services

National Toxicology Program (NTP): The NTP is formed from parts of several US government agencies, including the National Institutes of Health (NIH), the Centers for Disease Control and Prevention (CDC), and the Food and Drug Administration (FDA). The NTP updates its Report on Carcinogens (RoC) every few years.

2019 restudy on Roundup and generics on human cells. “Both European regulatory agencies and the USEPA have described GLY as unlikely to pose a carcinogenic hazard to humans…

Gly and its formulations decreased cell viability and induced cell death at concentrations of 10mM or above. Our positive controls for oxidative stress and DNA damage induced changes in these pathways at concentrations below those that altered cell viability. Gly and its formulations did not induce DNA damage and oxidative stress.”

“There was no evidence of genetic or reproductive toxicity of glyphosate.”

14th Report on Human Carcinogens.

Environmental Protection Agency

Revised Glyphosate Issue Paper: Evaluation of Carcinogenic Potential EPA’s Office of Pesticide Programs December 12, 2017

“The available data at this time do not support a carcinogenic process for glyphosate. Overall, animal carcinogenicity and genotoxicity studies were remarkably consistent and did not demonstrate a clear association between glyphosate exposure and outcomes of interest related to carcinogenic potential. In epidemiological studies, there was no evidence of an association between glyphosate exposure and numerous cancer outcomes; however, due to conflicting results and various limitations identified in studies investigating NHL, a conclusion regarding the association between glyphosate exposure and risk of NHL cannot be determined based on the available data. “ 216 page report

Food and Drug Administration (

“One international organization (the International Agency for Research on Cancer) concluded that glyphosate may be a carcinogen, while several others, including the European Food Safety Authority and the Joint Food and Agriculture Organization (FAO)/World Health Organization (WHO) Meeting on Pesticide Residues (JMPR), have determined that it is unlikely to be a carcinogen.

Results for both FY 2016 and FY 2017 assignment samples for glyphosate and glufosinate testing showed no pesticide residue violations for glyphosate in all four commodities tested (corn, soybeans, milk, and eggs).”

Spain, 1998-2002: “farmers exposed to non‐arsenic pesticides were found to be at increased risk of lymphoma.” Exposed for more than 9 years to “non arsenic pesticides; carbamates, organophosphates, chlorinated hydrocarbons (as pesticides), triazines and triazoles, phenoxy herbicides, chlorophenols, dibenzodioxin, and dibenzofuran.” All banned by the EPA in late 1980-1990.

National Toxicology Program, Department of Health and Human Services

Substances Listed in the Fourteenth Report on Carcinogens. Glyphosate is not on either list of;

                Known To Be Human Carcinogens

                Reasonably Anticipated To Be Human Carcinogens

National Pesticide Information Center

“Is glyphosate likely to contribute to the development of cancer?

Animal and human studies were evaluated by regulatory agencies in the USA, Canada, Japan, Australia, and the European Union, as well as the Joint Meeting on Pesticide Residues of the United Nations and World Health Organization (WHO). These agencies looked at cancer rates in humans and studies where laboratory animals were fed high doses of glyphosate. Based on these studies, they determined that glyphosate is not likely to be carcinogenic.”

National Library of Medicine

2000, Dr. Williams et. al.

“Safety evaluation and risk assessment of the herbicide Roundup and its active ingredient, glyphosate, for humans

It was concluded that, under present and expected conditions of use, Roundup herbicide does not pose a health risk to humans.”

World Health Organization, International Agency for Research on Cancer (IARC)

Monograph on Glyphosate. In March 2015, IARC classified glyphosate as “probably carcinogenic to humans” (Group 2A). “is based on the systematic assembly and review of all publicly available and pertinent studies…”

U.S. National Library of Medicine, National Institutes for Health

2019, Dr. Zhang et. al.

“Exposure to Glyphosate-Based Herbicides and Risk for Non-Hodgkin Lymphoma: A Meta-Analysis and Supporting Evidence

…our current meta-analysis of human epidemiological studies suggests a compelling link between exposures to GBHs and increased risk for NHL.”

Now for the alternatives.

This is a spreadsheet that helps compare relative costs per gallon of finished product. These are wholesale, commercial prices from last year and are used only for comparison. The prices have increased since assembling this data.

These are non-selective herbicides used in the landscape. Roundup is the only one on the list that is truly systemic and kills roots-and-all of weeds and grasses. All the alternatives are top-burners. I have tried them all and they do what they claim. Note the higher rates and prices. So, if a landscape maintenance company switches from Ranger to organic Axxe, they would be paying 20 times more per gallon of finished spray.

Also notice the Signal Words. Several of the alternatives require personal protection equipment to prevent skin burning and blindness.

Now, let’s put things in perspective. Pesticides are a small part of solving lawn and garden problems.  When we see plants in peril we need to consider numerous facts: Is it the right plant for this space? What is the quality of the soil, how is it being watered, how old is the plant, how was it planted, what’s going on below ground, what are those insects (good or bad) and the over arching question: Is this normal? Once you have solved those dozen problems then you decide on a response. If insect or disease control is warranted, then what is the best approach?


My first job as a teenager was working in a garden center in Michigan. One year I unloaded and sold over 2000 fresh cut Christmas trees, shoveled snow, loaded bags of soil in customer’s cars and stocked shelves. In the spring we would roll out tons of fertilizer and hundreds of cases of pesticides. That job began my education about lawn and garden problems and solutions. To formalize my training, I attended MSU and graduated from their landscape and nursery management program.

During the 1970’s we were all becoming aware of the environment and the effect certain pesticides had on the farm and food and water and wildlife. I was an early adopter of the organic gardening movement. I still have a lapel pin from the Rodale institute for a letter I wrote to Organic Gardening magazine. In my library I cherish a hardbound copy of Rachel Carson’s book “Silent Spring.”

In 1972 DDT was “issued a cancellation order” in the US because of its persistence in the environment and in people.  Its ability to move in water and the air landed it miles away from its target and moved throughout the food chain. Even though it has a half-life of over 7 years, it is still manufactured and approved for mosquito control in India and Africa.

In 2000 Dursban was no longer to be used indoors. The EPA phased out residential, home garden use in 2003. It is still legal to use in nurseries in soil against fire ants and other soil insects.

Dursban and Diazinon belong to the group of insecticides called organophosphates (OPs) They are chemical substances originally produced by the reaction of alcohols and phosphoric acid. OP’s were used as insect control in the 1930’s. The German military developed these substances as neurotoxins in World War II. They function as cholinesterase inhibitors, thereby affecting neuromuscular transmission. The U.S. EPA is giving priority to manufactures who come up with alternatives to the OP’s.

So, every licensing body of every country has the right and responsibility to approve pesticides before they are sold and used. And they all limit exactly how and where they are to be used. Just like all national laws, each state can enact stricter laws, and each city can enforce its own ordinances too.

Imidacloprid: Systemic and targets sucking insects like scale, whitefly, mealybug, thrips, aphids. Is highly soluble but adheres to soil for months. Is absorbed through roots, leaves, etc.

When used as a soil drench, where does it go?
Active IngredientTrade Name(s)
dinotefuranSafari, Zylam
imidaclopridMerit, Dominion, Grubs Away, Mallet, Bandit, Benefit, Marathon, Lada, etc.
thiamethoxamMeridian, Flagship
The five neonicotinoids.
How long do they last?
Tristar (acetamiprid) is the least disruptive to bees.

Alternatives to neonicotinoids for residential application:



Insecticidal oil

Insecticidal soap


Met 52


Insect Growth Regulators: Talus, Tekko