Short answer: wash melons, watermelons and avocados before you cut them. With bananas, clean hands matter most. Do you need to wash bananas under the faucet as well? If you peel them by hand and never cut through the skin with a knife, there is very little to gain. The logic is the same for all three fruits: bacteria get from the skin into the flesh mostly on the knife and on your hands.
Washing something you won’t eat can feel pointless. Then consider 2011, when 147 people in 28 US states caught listeriosis from cantaloupes, the melons with the netted rind. Thirty-three of them died. The source was whole melons from a single farm in Colorado. What investigators found at that farm, and why a private auditor had scored it 96 out of 100 a week before harvest, is covered in our piece on the Jensen Farms cantaloupe outbreak.
How bacteria get from the rind to the flesh
A knife passes through the rind and carries whatever was on the outside along its blade. That is why the US Food and Drug Administration (FDA) tells people to rinse produce before peeling it, so dirt and bacteria aren’t transferred from the knife onto the fruit.
Researchers at the US Department of Agriculture tested this on cantaloupes in two studies. In 2001 they contaminated melons with Salmonella, and pieces cut from untreated melons carried Salmonella too. In 2002 they used Listeria. It survived on the rind for up to 15 days, both in the fridge and at 68°F (20°C). Pieces cut from melons kept at 39°F (4°C) for a day after contamination tested positive.
A 2024 review by Australian researchers sums up the usual outbreak route: melons get contaminated on the farm, and the bacteria reach the flesh during cutting and processing.
Why melons and watermelons carry the most risk
According to the same review, two things make cantaloupe vulnerable. In its final growth phase it sits in close contact with the soil, and its netted rind is full of crevices. Listeria clings firmly inside those crevices and forms a biofilm. What a biofilm is, and why water struggles to shift it, is covered in our piece on biofilms on produce.
Melon outbreaks keep turning up:
- 2018, Australia: 22 cases of listeriosis and 7 deaths, again traced to a single farm.
- 2021, United Kingdom: 113 cases of salmonellosis linked to Galia melons from Latin America, a third of them admitted to the hospital.
- 2021, United Kingdom: 17 cases of Shiga toxin-producing E. coli linked to pre-cut watermelon.
- 2023, United Kingdom and Portugal: 98 cases of salmonellosis linked to cantaloupe, 46% of them children under 10.
- 2023, United States: more than 400 people ill, 158 hospital admissions and 6 deaths across 44 states from cantaloupes carrying Salmonella.
One growing area in south-west Indiana has now been linked to four salmonellosis outbreaks from cantaloupes or watermelons since 2012. The team that investigated the 2023 outbreak in Britain and Portugal notes that large Salmonella outbreaks linked to melon are being identified more and more often.
What water does, and what a brush adds
The honest part first: water on its own does little on a netted rind. In the 2001 study, washing with water did not reduce Salmonella on the rind. In a 2012 study at Texas A&M University, neither tap water nor chlorine reduced Salmonella numbers on the rind.
The FDA advises scrubbing firm produce such as melons and cucumbers with a clean brush under running water. A brush removes noticeably more than soaking, though it can spread bacteria itself if you don’t clean it. The figures are in the same piece on biofilms.
In a 2020 study at the University of Georgia, rind pieces that had just been washed with water passed significantly more Listeria to the flesh via a gloved hand than unwashed pieces did. So after washing, dry the melon with a clean cloth or a paper towel, as the FDA recommends. How damp surfaces hand bacteria on is explained in our piece on kitchen cross-contamination.
Skip the soap, detergent and commercial produce washes. The FDA does not recommend them: produce is porous, and soap or detergent can be absorbed even after a thorough rinse. Whether veggie wash sprays help is covered separately.
For what it’s worth, in a 2002 US survey more than 35% of respondents said they don’t wash melons before preparing them.
How to cut a melon so less gets through
The order of cutting matters too. In the Texas study, less Salmonella reached the flesh when the rind was peeled off first and the flesh cut afterward. Cutting the melon up with the rind on and trimming the rind later did worse.
A University of Delaware team compared two methods. The first is the familiar one: cut the melon into eighths, slice off the rind and cube the flesh with the same knife. In the second, the melon was scored around its middle, pulled apart by hand, and the flesh scooped out with a spoon so it never touched the spot where the rind had been. The second method left roughly ten times less Listeria and Salmonella in the flesh. The authors call the gain small and stress that the real priority is keeping whole melons from getting contaminated.
A word on the stem end. In the Texas work, the stem scar carried roughly 30 times more Salmonella than the rest of the rind. Give that spot extra attention when you wash.
Cut melon goes straight in the fridge
In the 2002 study, Listeria on cantaloupe cubes survived for 15 days at 39°F (4°C) but did not grow. At 46°F (8°C) and 68°F (20°C), growth was visible within 4 hours.
FDA scientists compared Listeria growth across a dozen or so cut vegetables and fruits, from broccoli to olives and button mushrooms. It grew fastest in cantaloupe flesh and avocado pulp. And a 2025 risk model for ready-to-eat diced cantaloupe found that poor storage at home can raise the risk by up to 500-fold.
The summer takeaway: put cut watermelon or melon in the fridge straight away. When you buy half a watermelon, pick one from a chilled display or surrounded by ice, as the FDA advises. Why hot weather matters so much for gut infections is explained in our piece on why summer is outbreak season.
Avocados: the skin is dirtier than it looks
Between 2014 and 2016 the FDA tested 1,615 avocado samples, about 70% of them imported. Listeria turned up on 64 of 361 skin samples, or 17.73%. In the pulp it was found in 3 of 1,254 samples, or 0.24%, and all three came from imported fruit. Salmonella was found in 12 of the 1,615 samples.
The FDA says it plainly: if Listeria is on the skin, slicing and handling the fruit could carry it into the pulp. The University of Georgia tested this in 2026. Straight after cutting, 0.4-0.7% of the bacteria on the skin had moved into the pulp, and the type of knife made no difference. That sounds tiny. Yet in one arm of the study, Listeria in the pulp grew more than 10,000-fold over 21 days in the fridge. Salmonella, by contrast, declined over the same period.
With avocados, water did noticeably better in the lab. In a 2011 Mexican study, 15 seconds under a spray of tap water cut Salmonella, E. coli and Listeria on Hass avocados by roughly 4,000 to 6,000 times. A follow-up chlorine spray added nothing more. In its report, the FDA counts avocados among the firm produce that FoodSafety.gov says should be scrubbed with a clean brush and then dried.
There is a limit washing can’t get past. In FDA lab work, Listeria moved into the pulp through the stem end, both when it was applied directly to the stem scar and when the fruit was cooled in contaminated water, as can happen after harvest. After 15 days at 39°F (4°C) it was found in the pulp next to the stem scar. No amount of rinsing reaches bacteria that are already inside.
As of 2021, avocados had not been identified as the source of any Listeria outbreak in the United States. Even so, CDC and FDA scientists examined five genetic clusters of cases that included avocado isolates, and judged the link likely or possible in three of them. This matters more for pregnant women, older adults and people with weakened immune systems: according to the FDA, even small amounts of Listeria can make them ill. How few bacteria it can take is covered in our piece on infectious dose.
Bananas: where washing adds the least
You peel a banana by hand, and a knife rarely goes through the skin. We searched PubMed and found no documented foodborne outbreaks traced to bananas. Hands are the main route here, and the FDA advises washing them with soap for 20 seconds before and after handling fresh produce.
Pesticide residues follow a similar pattern. In field trials in China, banana peel held 2.2 to 12.3 times more of the fungicide difenoconazole than the pulp, and 1.1 to 7.7 times more prochloraz. The peel goes in the trash along with those residues. In a 2023 study on bananas ripening after harvest, the non-systemic fungicide thiram stayed in the peel. Systemic pesticides, however, started moving into the fruit within 6 hours, and washing the skin won’t remove them. The widest gap between appearance and chemistry is not in produce at all: cut flowers carry no residue limits whatsoever.
Rinse a banana when you plan to cut it with the skin on, say, in half for a child. Strictly speaking, the FDA advises washing all produce, including anything you’ll peel, so rinsing a banana is never wrong. It just does the least good here.
Step by step
- Wash your hands with soap for 20 seconds.
- Rinse melons, watermelons and avocados under running water and scrub them with a clean brush. No soap.
- Pay extra attention to the stem end of a melon.
- Dry the fruit with a clean cloth or a paper towel.
- Use a clean knife on a clean board. Take the rind off a melon before cubing it, or pull the melon in half and scoop the flesh out with a spoon.
- Put anything you’ve cut in the fridge straight away.
- Peel bananas with clean hands, and rinse them if you’re cutting through the skin.
- Wash the brush when you’re done.
Summary
Nobody eats the rind, but knives and hands carry bacteria from it into the flesh. The biggest risk sits with netted melons: scrub them, dry them, cut them so the flesh stays away from the rind, and keep cut pieces in the fridge. Wash avocados before slicing too, especially if someone at home is pregnant or elderly. For bananas, clean hands usually do the job.
The wider picture of fresh produce risk is in our food safety hub.
A cut melon moves into a category for which the Food Code requires 41 °F. Why the knife changes the instruction more than the variety does is covered here.
