A single laboratory test cannot screen for every chemical used in modern agriculture. Here’s why our community-funded testing programme focuses on glyphosate.
After publishing our recent potato testing results, one of the most common questions we received was:
“Why didn’t you test for other chemicals as well?“
It’s a fair question.
The answer starts with understanding just how many different chemicals can be involved in growing a modern potato crop.
How Many Chemicals Can Be Used on Potatoes?
Most consumers think of a potato as one of the simplest foods available.
Dig it out of the ground, wash it, cook it and eat it.
The reality is considerably more complex.
Potatoes are vulnerable to a wide range of diseases, insects and weeds. To maintain yields and protect crop quality, growers have access to numerous fungicides, insecticides and herbicides throughout the growing season.
Fungicides are often the most heavily used category.
Late blight alone can devastate a potato crop. To manage this risk, growers may apply fungicides multiple times during a season. Products used in potato production have included active ingredients such as mancozeb, metalaxyl-M, azoxystrobin, chlorothalonil, fluazinam, copper compounds, difenoconazole and others.
Insect control adds another layer.
Potato growers may need to manage aphids, tomato potato psyllid (TPP), potato tuber moth and other pests. Depending on the situation, products can include active ingredients such as imidacloprid, pirimicarb, pymetrozine, spirotetramat, cyhalothrin and others.
Then there are herbicides.
Weed competition can significantly affect crop yields, leading to the use of herbicides containing active ingredients such as metribuzin, glyphosate, diquat and other herbicides.
Potato production can also involve seed treatments before planting, storage treatments and sprout suppressants may be used after harvest.
The point is that modern agriculture involves a large number of possible chemical inputs, each designed to solve a specific problem.
Most consumers never see that complexity.
By the time fungicides, insecticides, herbicides, seed treatments and storage treatments are considered, the number of potential residues quickly becomes far larger than most people realise.
Why Testing Potatoes for Pesticides Is More Complicated Than It Sounds
This is where laboratory testing becomes complicated.
Many people understandably assume a laboratory can simply test a food sample for “pesticides.”
In reality, there is no single test that covers everything.
Different chemicals behave differently in the laboratory. Some are easier to detect using one analytical method, while others require entirely different extraction, preparation and detection techniques.
A test designed to find glyphosate is not automatically testing for mancozeb.
A test designed to find mancozeb is not automatically testing for chlorpropham.
A test designed to find chlorpropham is not automatically testing for imidacloprid.
Each additional group of chemicals often requires additional laboratory methods, equipment, validation processes and reporting.
That is why laboratories offer multiple testing suites rather than one universal test.
Why Comprehensive Pesticide Testing Costs So Much
Our potato testing was carried out by Hill Laboratories using a method specifically designed to analyse glyphosate, its primary breakdown product AMPA, and the related herbicide glufosinate.
The laboratory analysis for glyphosate, AMPA and glufosinate typically costs around $400 per sample.
Broader residue screening requires additional testing suites.
A laboratory may need to run separate multi-residue screens covering hundreds of different compounds, together with additional targeted tests for chemicals that are not included in those screens.
Before long, the cost can climb from hundreds of dollars to thousands.
That may be appropriate for exporters, regulators, researchers or commercial quality assurance programmes.
For a community-funded project, those costs matter.
Why NMGNZ Focuses on Glyphosate
No More Glyphosate NZ was created to increase public understanding of glyphosate, its use in New Zealand, and the evidence surrounding its presence in food, public spaces and the wider environment.
Our supporters donate because they want independent testing and reporting focused on glyphosate exposure in New Zealand food and the wider environment.
Every testing project therefore involves choices.
Do we spend thousands of dollars testing a handful of samples for hundreds of chemicals?
Or do we use those same funds to test a larger number of products for glyphosate, allowing us to build a broader picture of glyphosate exposure across the food supply?
Our mission is in our name.
We investigate glyphosate exposure in New Zealand food and the environment, and our testing programme is designed around that purpose.
What the Potato Testing Discussion Reveals
The potato discussion highlights something important.
When people ask why we did not test for dozens of other chemicals, they are indirectly acknowledging a reality that often receives little public attention.
Modern food production can involve a large number of chemical inputs.
Understanding what those chemicals are, why they are used, how much remains on food, and whether consumers should be concerned is a much bigger conversation than any single laboratory result.
Our recent potato testing answered one specific question.
Were glyphosate, AMPA or glufosinate detected in the potato samples tested?
No glyphosate, AMPA or glufosinate were detected in the samples tested above the laboratory reporting limits.
But the discussion that followed reminds us that many New Zealanders are increasingly interested in understanding the wider chemical footprint behind the food they eat.
That is a conversation worth having.
Further Reading
The discussion surrounding our potato testing results highlights a broader challenge facing consumers today.
Most people want simple answers. Is food safe? What chemicals are being used? What do testing results actually tell us?
The reality is often more complicated.
Modern food production involves a wide range of agricultural chemicals, different testing methods, regulatory limits, and scientific debates about exposure and risk. Understanding those issues requires looking beyond any single laboratory result.
The following articles explore some of those questions in greater detail.
Support Independent Testing
Community-funded testing projects are only possible because readers choose to support them. If you would like to help fund future testing and reporting projects, please consider supporting No More Glyphosate NZ:
👉 Like What We’re Doing? Support NMGNZ
More Independent Testing Results
Explore the results of our previous food testing projects:
👉 Testing Results
Understanding Glyphosate Exposure
Why New Zealand Needs a Glyphosate Reality Check:
Insights from Dr. Jodie Bruning
A closer look at why exposure, monitoring, and public understanding of glyphosate remain important topics in New Zealand.
Reducing Exposure Through Food Choices
How to Reduce Glyphosate Exposure in Food: A Practical Guide
Practical steps New Zealand consumers can take if they wish to reduce potential dietary exposure.
What Washing and Cooking Can — and Can’t — Do
Washing, Cooking, Freezing — What These Steps Really Do for Pesticides
An evidence-based look at how common food preparation methods affect pesticide residues.
Does Cooking Remove Pesticides from Food? A Closer Look
A deeper examination of what happens to pesticide residues during cooking.
Can You Wash Glyphosate Off Your Food? If Only It Were That Simple
Why removing glyphosate residues is often more complicated than simply washing produce.
A Bigger Question
One of the most interesting lessons from the potato testing project was not the laboratory result itself.
It was the number of people who immediately wanted to know what else might be present.
That question reflects a growing public interest in understanding how food is produced, what chemicals are used throughout the process, and how much transparency consumers should expect.
Whether that conversation leads to more testing, better monitoring, or simply more informed choices, it is a conversation that is unlikely to disappear anytime soon.
Image Source & Attribution
We’re grateful to the talented photographers and designers whose work enhances our content. The feature image on this page is by SashaKhalabuzar.
