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Australian scientist tested supermarket berries for pesticide residues
When Professor Kirsten Benkendorff from Southern Cross University was testing waterways near blueberry farms for her marine science research, she detected pesticides in the creeks, crabs, and oysters. That raised a question: if these chemicals were showing up in the marine environment, were they also getting into the berries themselves?
So she did something straightforward—she bought punnets of blueberries and raspberries from supermarkets in northern NSW and had them tested at a NATA-accredited laboratory in Sydney. What she found has sparked important conversations about pesticide residues in Australian produce, regulatory oversight, and what consumers deserve to know about the food we're eating.
Here's what the testing revealed, why it matters for Australian families, and what's happened since.
What the Testing Found
Professor Benkendorff purchased berries from Woolworths, Coles, Aldi, and local fruit shops across northern NSW in November 2024. She tested 17 batches total: 12 blueberry samples, 5 raspberry samples, and 1 blackberry sample. The berries came from six different suppliers in northern NSW.
All samples contained between 4-11 different pesticides. The screening tested for 157 pesticides and detected 22 different types across all samples.
Two findings particularly stood out:
Dimethoate: Three blueberry samples contained dimethoate—a neurotoxic organophosphate pesticide—at levels where a 20kg child would exceed the Acceptable Daily Intake (ADI) after eating just a handful of berries. An 80kg adult would exceed it after eating 50-80 berries.
Dimethoate has been used since the 1950s to control fruit flies. It's legal in Australia but was banned in the EU in 2019 after the European Food Safety Authority concluded its use posed a risk to consumers, operators, and workers. The US Environmental Protection Agency classifies it as a possible human carcinogen.
Thiometon: Six of 11 blueberry samples and all raspberry samples tested positive for thiometon, an insecticide that was deregistered in Australia in 1995 (banned from use in 2001) due to toxicity concerns. Thiometon is banned in 39 countries, including the EU and UK.
Worth noting: these tests were conducted on washed berries. The pesticides remained even after washing.
Why Washing Doesn't Remove These Pesticides
Berries have thin, semi-permeable skins. When systemic pesticides like dimethoate are applied, they're absorbed into the plant's vascular system and become part of the fruit tissue itself. Surface washing can remove some contact pesticides, but systemic pesticides are inside the berry—no amount of washing eliminates them.
Professor Benkendorff specifically tested washed berries to understand what consumers would actually be exposed to. The fact that multiple pesticides remained after washing shows why "just wash your produce" isn't sufficient advice for all fruits and vegetables.
Research published in the American Chemical Society's journal Nano Letters in 2024 found that peeling was the most effective way to eliminate pesticide residues from produce—but you can't peel berries.
The Regulatory Response and Industry Pushback
The findings prompted several responses:
APVMA Action: In March 2025, the Australian Pesticides and Veterinary Medicines Authority initiated a review of dimethoate use on berries. They proposed extending the pre-harvest withholding period from 1-7 days to 14 days for all berries. This means farmers must wait 14 days after spraying before harvesting.
The APVMA acknowledged this decision was based on updated berry consumption data. Previous regulations were based on 1995 consumption figures—nearly 30 years old—when Australians ate far fewer berries. Current data shows berry consumption has increased between 285-962% since then.
Industry Testing: Berries Australia, the industry group, conducted its own testing of 14 supermarket samples using FreshTest, an industry testing provider. They reported finding no thiometon and no breaches of legal residue limits.
EPA and Food Authority Response: In January 2025, the NSW EPA and NSW Food Authority released a joint statement reviewing Professor Benkendorff's findings. They stated that FreshTest data from the same testing period (October-November 2024) showed no evidence of thiometon, and claimed the research methodology "was not accredited for testing fresh fruit such as berries" and therefore results were "unreliable."
The NSW Food Authority announced plans to conduct additional testing on retail berries to confirm whether thiometon is present.
Understanding the Controversy
Here's where it gets complicated. Professor Benkendorff acknowledges her testing methodology differs from what wholesalers and growers typically use. She describes it as a "gold standard extraction method followed by a rigorous environmental contaminant screen" that can detect a wider variety of pesticides at lower levels—including pesticides like thiometon that aren't routinely tested for by the industry.
She maintains there is no evidence her testing is flawed and notes that her laboratory was NATA-accredited. The detection of thiometon, she suggests, may have resulted from contamination from spray drift or water contamination from neighboring properties, or from another product applied to crops.
Andrew Bell, managing director of blueberry farm Mountain Blue and president of the Australian Blueberry Growers Association, called the findings "devastating" for the industry and said it was "inexcusable" to publicly criticize an entire industry based on what he described as flawed methodology.
What's important to understand: Professor Benkendorff never claimed the berries exceeded maximum residue limits (MRLs) set by regulators. Her concern was that even at current allowable limits, some pesticides could exceed the Acceptable Daily Intake for people—particularly children—who eat berries regularly.
What This Reveals About Pesticide Regulation in Australia
Regardless of the thiometon controversy, several concerning patterns emerged from this situation:
Testing gaps: Australia discontinued comprehensive national pesticide residue testing in 2014. State-level testing is limited and sporadic. The most recent Australian Total Diet Study is underway but results won't be published until late 2025. This means we have limited data about what's actually on Australian produce.
Outdated consumption data: The APVMA was using 30-year-old berry consumption data when setting residue limits and withholding periods. Australians now eat dramatically more berries than in 1995, which means increased exposure to any residues present. The fact that it took an independent researcher's findings to prompt updated regulations raises questions about proactive monitoring.
Maximum Residue Limits vs Acceptable Daily Intake: As Professor Benkendorff pointed out, the maximum residue limits set for pesticides on berries are often higher than for other foods. When you combine higher MRLs with dramatically increased consumption, particularly among children, it's worth examining whether current limits adequately protect public health.
Detection of banned substances: The presence of thiometon—banned in Australia for over 20 years—in multiple samples (whether from contamination, spray drift, or other sources) suggests gaps in monitoring and enforcement.
Regulatory funding: Worth knowing—the APVMA is 87% industry-funded (as of 2023-24). This doesn't automatically mean decisions are compromised, but it's a factor in understanding how pesticide regulation operates in Australia.
What We Know For Certain
Setting aside the thiometon controversy, here's what's not in dispute:
- All berry samples contained multiple pesticides (4-11 different types)
- Dimethoate was present at levels that concerned a marine science professor enough to prompt regulatory review
- The APVMA extended withholding periods for dimethoate on berries, acknowledging the need for updated safety measures
- Berry consumption in Australia has increased dramatically since the last consumption data was compiled
- These pesticides remained on washed berries
- Australia lacks routine, comprehensive pesticide residue testing like the US USDA program
What This Means for Australian Families
If you regularly buy berries for your family—particularly for children who often eat large quantities—this information matters.
Berries are promoted as superfoods, packed with antioxidants and nutrients. They show up in school lunches, breakfast bowls, and smoothies. The health benefits are real. But the question Professor Benkendorff raised is valid: are we adequately accounting for increased consumption when setting pesticide limits?
The reality is that systemic pesticides in berries can't be washed off. A child eating a punnet of blueberries as a healthy snack could be consuming multiple different pesticides simultaneously. We don't fully understand the cumulative or synergistic effects of multiple pesticides consumed together.
Practical Guidance for Berry Shopping
Given what we know, here are the options:
Buy organic or spray-free berries when possible. This is the only way to avoid systemic pesticide residues. Look for Australian Certified Organic (ACO) or NASAA certification. Frozen organic berries are typically more affordable than fresh and nutritionally equivalent.
If organic isn't accessible or affordable:
- Wash berries thoroughly (though understand this won't remove systemic pesticides)
- Consider reducing frequency or portion sizes, particularly for young children
- Choose alternative fruits from the Clean Fifteen list (mangoes, pineapple, kiwi, papaya) which have lower pesticide residues. Learn more about which produce to buy organic
Ask questions: At farmers markets, ask growers about their spray practices. Many small farms use organic or low-spray methods without expensive certification.
Support better testing: Contact your representatives to advocate for reinstating comprehensive national pesticide residue testing. Consumers deserve routine, transparent data about what's on our food.
The Bigger Picture
Professor Benkendorff's research—whether you view it as flawed methodology or necessary independent investigation—highlighted something important: we need better, more transparent pesticide monitoring in Australia.
The fact that berry consumption data was 30 years out of date when setting safety limits is concerning. The fact that an independent scientist felt compelled to test supermarket berries because of what she found in waterways near farms raises questions about whether current monitoring is adequate.
This isn't about demonizing farmers or the berry industry. Growing food is challenging, pest pressure is real, and farmers work within the regulatory framework they're given. But consumers deserve accurate information about what's on the food we're eating, particularly when we're feeding it to children.
The extended withholding periods for dimethoate show that concerns about berry pesticides were legitimate enough to warrant regulatory changes. Whether or not thiometon is definitively present, the conversation about pesticide limits, testing frequency, and cumulative exposure is one worth having.
Which berries do your children eat most often? This might be a good time to check whether organic options are available in your area—or consider some of those Clean Fifteen alternatives like mangoes or kiwi that offer similar nutritional benefits with lower pesticide concerns.