Potatoes have been one of the most requested foods in our independent testing programme.
Over the past year, we’ve received numerous messages from people concerned about pesticide use in potato production. Some readers have told us they avoid potatoes altogether because they believe the crop is heavily sprayed. Others have asked whether glyphosate residues are likely to be present in the potatoes found on supermarket shelves.
Rather than speculate, we decided to find out.
Three different potato products purchased from Woolworths New Zealand were independently tested for glyphosate by Hill Laboratories. The results were straightforward: none of the samples contained detectable glyphosate above the laboratory’s reporting limit.
Potato Glyphosate Test Results
All three potato samples returned non-detect results for glyphosate.
| Sample | Result |
|---|---|
| Woolworths Fresh Vegetable Potatoes Agria | Not Detected (<0.010 mg/kg) |
| Woolworths Fresh Vegetable Potatoes Low Carb | Not Detected (<0.010 mg/kg) |
| Woolworths Fresh Vegetable Potatoes Red | Not Detected (<0.010 mg/kg) |
Testing was performed using LC-MS/MS analysis with a glyphosate reporting limit of 0.010 mg/kg.
In simple terms, glyphosate was not detected in any of the three potato samples above the laboratory’s reporting limit.
What Does “Not Detected” Actually Mean?
One of the most common questions we receive whenever a result comes back clean is whether “not detected” means absolute zero.
The answer is no.
A non-detect result means glyphosate was not found above the laboratory’s reporting limit. In this case, any glyphosate present would have been below 0.010 mg/kg, equivalent to 10 parts per billion.
That doesn’t prove glyphosate is absent from every potato grown in New Zealand or imported into the country. It simply tells us that glyphosate was not detected in these specific samples at the sensitivity used by the laboratory.
For consumers, however, that is generally considered a reassuring result.
Why Test Potatoes for Glyphosate?
Potatoes occupy an interesting place in the pesticide debate. Unlike oats, wheat, barley, and some other crops that are frequently discussed in relation to glyphosate use, potatoes are more commonly criticised because they may receive a range of fungicide, insecticide, and other crop protection treatments during production. Nevertheless, they were among the most frequently requested foods in our testing programme.
As a result, many consumers assume pesticide residues are inevitable. Whether that perception is entirely fair or not, it raises a reasonable question: what can actually be detected in the potatoes available for purchase?
Our results serve as a useful reminder that pesticide use and pesticide residues are not necessarily the same thing. A crop may receive treatments during production while still producing a non-detect result for a particular chemical at harvest.
Assumptions can point us toward questions worth asking, but only testing can provide answers.
Do Non-Detect Glyphosate Results Mean Potatoes Are Chemical-Free?
From a glyphosate perspective, these results are encouraging.
All three potato varieties tested returned non-detect results, providing no evidence of measurable glyphosate residues in these samples at the laboratory’s reporting limit of 0.010 mg/kg.
However, glyphosate is only one of many agricultural chemicals that may be used during food production. When readers contact us about potatoes, their concerns often extend beyond glyphosate and include fungicides, insecticides, sprout suppressants, and other crop protection products that may be used during growing, storage, or transport.
It is also important to recognise that different pesticides behave differently. Glyphosate is a systemic herbicide, meaning it is absorbed and moved throughout plant tissues. Other agricultural chemicals may act in different ways, with some remaining largely on the crop surface, some breaking down over time, and others being applied at entirely different stages of production.
As a result, a non-detect glyphosate result does not necessarily tell us what may or may not be present for other agricultural chemicals.
For that reason, these results should not be interpreted as proving that potatoes are entirely free from agricultural residues. They simply tell us that glyphosate was not detected in the samples tested.
Determining whether other pesticide residues are present would require broader laboratory screening, which is considerably more expensive and falls outside the scope of this particular round of testing.
Whether additional testing would provide meaningful insights for consumers is something we are currently considering. As Canada moves toward continuous oversight of glyphosate, questions about how pesticide residues are monitored and measured are likely to become increasingly relevant in New Zealand as well.
Why Independent Food Testing Matters
It would be easy to focus only on positive detections. After all, findings tend to attract more attention than clean results.
However, transparency works both ways. When residues are detected, we publish the results, and when residues are not detected, we publish those results too. Both outcomes contribute to a more accurate understanding of what consumers are actually buying and eating.
The purpose of independent testing is not to confirm a predetermined belief but to gather evidence and follow where it leads.
Sometimes that evidence raises concerns. Sometimes it provides reassurance. Either way, consumers are better served by access to information than by assumptions about what may or may not be present in their food.
What These Potato Test Results Tell Us
The takeaway from this round of testing is straightforward.
The three potato products tested all returned non-detect glyphosate results at a reporting limit of 0.010 mg/kg.
That is good news.
At the same time, the results leave us with a broader question about the range of agricultural chemicals that may be used in potato production and whether consumers would benefit from additional testing beyond glyphosate alone.
For now, though, the evidence we have is clear.
These three potato samples contained no detectable glyphosate.
Sometimes the most interesting result is the one people weren’t expecting.
Testing Costs & Transparency
| Item | Cost |
|---|---|
| Woolworths Fresh Vegetable Potatoes Red (2kg) | $8.75 |
| Woolworths Fresh Vegetable Potatoes Low Carb (2kg) | $9.99 |
| Woolworths Fresh Vegetable Potatoes Washed Agria (2kg) | $9.75 |
| Hill Laboratories testing | $1,196.29 |
| Courier costs | $25.80 |
| Total Cost | $1,250.58 |
Community donations help cover the laboratory testing costs, while No More Glyphosate NZ funds the remaining expenses associated with purchasing products, sample preparation, and shipping.
This potato testing project was only possible because supporters helped fund the laboratory analysis. If you’d like to help us test more foods and continue building an independent picture of what’s in New Zealand’s food supply, please consider supporting future testing by making a contribution through our Support No More Glyphosate NZ page.
Why were 2kg bags purchased?
Hill Laboratories requires a minimum sample size for this type of testing, and for this type of analysis, the laboratory requires 2kg of potatoes.
Image Source & Attribution
The feature image on this page was created by No More Glyphosate NZ using licensed stock photography and additional graphic elements, which were combined and edited in Canva for publication.
