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The diet explains the infestation: almost nothing organic is off the menu.

What Do Roaches Eat? Diet, Digestion, and Why They Survive on So Little

Roaches are generalist omnivores that eat food residue, paper, glue, dead insects, and each other's droppings. What the research says, and what it means.

12 min read

Cockroaches are generalist omnivores. NC State Extension describes the German cockroach as feeding on everything from "breadcrumbs, plant material, and dead insects, to decomposing material from trash cans." UF/IFAS Extension says the American cockroach "consumes decaying organic matter but is a scavenger and will eat almost anything," and lists observed foods including paper, hair, bread, fruit, book bindings, cloth, and dead insects. Two biological features make that breadth possible: a bacterial endosymbiont that recycles nitrogen from their own waste, and a gut microbiome that reorganizes itself around whatever they are eating. Water is the harder constraint. Roaches last far longer without food than without moisture.

The earlier version of this article said roaches eat 4 to 5 milligrams of food per day and can survive three months on water alone. We could not find support for either figure, so this version drops them and uses what extension and peer-reviewed sources actually report. It also removed the claim that cucumber, garlic, and coffee grounds repel roaches, which is not supported by the sources we reviewed.

This guide is about diet and digestion. For the conditions in a home that draw roaches in and how to remove them, see what attracts roaches.

What Roaches Eat in a House

Penn State Extension describes German cockroaches as scavengers "especially fond of starches, sweets, grease, and meat products." In practice, that means:

  • Crumbs, spills, and grease films on and behind cooking appliances.
  • Dirty dishes and standing dishwater.
  • Garbage and food residue in the can itself, and rinsed-but-not-clean recyclables.
  • Pet food in bowls and in bags.
  • Fruit, especially fermenting fruit. University of Minnesota Extension notes American cockroaches like fermenting foods, giving the example of bread soaked with beer.
  • Anything left out overnight, since roaches are nocturnal foragers.

The amount required is small. A German cockroach is roughly half an inch long, so a population can persist on residue that a person would not register as food at all. That is why grease behind a range matters more than an obvious crumb on a counter.

The Non-Food Items They Will Eat

The list from UF/IFAS Extension for the American cockroach is the most specific in the extension literature. It prefers sweets, "but has also been observed eating paper, boots, hair, bread, fruit, book bindings, fish, peanuts, old rice, putrid sake, the soft part on the inside of animal hides, cloth, and dead insects."

UF/IFAS separately notes that the German cockroach is omnivorous, "eating table scraps, pet food, and even book bindings."

The common thread in the non-food items is starch, protein, or cellulose: paper and cardboard, bookbinding paste and other glues, fabric, leather, hair and skin flakes, and soap residue. None of these are preferred foods. They are what a starch-and-protein-seeking scavenger falls back on when better options are gone, which is why a clean but cluttered storage room can still support roaches.

Do Different Species Eat Different Things?

Less than commonly claimed. All four house-infesting species in the United States are opportunistic omnivores, and the differences in the research are mostly about where they forage rather than what they prefer.

  • German cockroach. Indoors, near kitchens and bathrooms. NC State calls it a generalist omnivore that forages within the aggregation's range of food and water.
  • American cockroach. Sewers, drains, mulch, tree holes, and commercial kitchens. Strong preference for sweets and fermenting material, plus the broad scavenging list above.
  • Oriental cockroach. Damp, cool, ground-level sites. Penn State notes they favor dark, damp, cool areas such as those under sinks and washing machines, and outdoors live beneath leaves and in bark mulch around shrubs, where decaying organic matter is the available food.
  • Smokybrown cockroach. Outdoor in moist protected habitat. University of Tennessee Extension notes they feed on animal feces, which is one reason they are treated as a public health pest.

Confident claims that one species has a "sweet tooth" and another prefers starch do not hold up well against the actual research, where the biggest measurable differences are in nutrient balancing and learned preferences rather than species-level menus.

Roaches Balance Nutrients, They Do Not Just Consume Calories

A 2017 laboratory study in the *Journal of Experimental Biology* gave German cockroaches two nutritionally lopsided foods, one higher in protein and one higher in carbohydrate, and measured what they ate. The insects adjusted their intake of each nutrient depending on life stage and on how far they had to walk between the two foods. That is regulated feeding, not indiscriminate eating.

NC State Extension notes a related pattern: adult females consume large amounts of food while developing eggs, roughly five times what adult males eat, and then reduce intake. Demand varies with what the insect is doing.

Diet also reshapes their internal biology. A 2015 study in *FEMS Microbiology Ecology* fed German cockroaches diets with zero, 24, and 50 percent protein and found the gut bacterial community reassembled in a diet-specific manner within days. Wild-caught cockroaches showed the highest microbial diversity, consistent with the most varied diets.

The Bacteria That Make an Omnivore Out of a Scavenger

Cockroaches carry an obligate bacterial endosymbiont, Blattabacterium, in their fat body. A 2009 *PNAS* study sequenced its genome from the American cockroach and found that it recycles nitrogen from urea and ammonia, the breakdown products of the uric acid cockroaches store as waste, and can then produce all of the essential amino acids plus various vitamins from a limited set of substrates.

The authors' conclusion is the useful part for a homeowner: this ancient partnership "has allowed cockroaches to subsist successfully on nitrogen-poor diets and to exploit nitrogenous wastes, capabilities that are critical to the ecological range and global distribution of cockroach species."

In plain terms, a cockroach can live on food that is nutritionally close to garbage because it carries a factory for the nutrients that garbage lacks. This is the biological reason that cleaning alone rarely starves out an infestation.

Feces, Dead Roaches, and Cannibalism

Three feeding behaviors that sound like tabloid material are well documented and genuinely matter for control.

  • Coprophagy. Young nymphs eat adult droppings. A 2023 review in the *Journal of Economic Entomology* reports that first instars can develop into second instars solely on adult feces, gaining both nutrients and the gut microbes they need. NC State describes droppings as concentrated nutrient sources that also transfer gut microflora.
  • Necrophagy. Cockroaches scavenge dead insects, including dead cockroaches. Field-collected specimens have been found with arthropod cuticle in their digestive tracts.
  • Cannibalism. Uncommon under normal conditions, but it occurs under crowding and food scarcity.

These behaviors are why baits kill more roaches than eat them. The same review notes that nymphs readily ingest the feces of adults that fed on hydramethylnon bait, producing secondary mortality above 85 percent in some experiments, with tertiary mortality from nymph-to-nymph transfer ranging from 15 to 70 percent depending on the active ingredient. Bait works partly as a food and partly as a contaminant moving through a population that eats its own waste.

How Long Can Roaches Go Without Food or Water?

Water is the binding constraint. Penn State Extension states that oriental cockroaches with access to water "can live for a month without food; without water, they die within two weeks."

A 2026 study in the *Journal of Economic Entomology* from the University of Kentucky tested German cockroach survival across combinations of diet, temperature, relative humidity, and life stage. Lower temperatures produced the longest survival times. When no food or water was available, higher relative humidity extended survival, and at higher humidity, cockroaches with food access survived considerably longer than those without. The authors frame the work as clarifying "how long infestations can persist in homes" and the role sanitation plays in management.

The practical reading: a cool, damp, empty space is the best place for a starving roach population to wait you out, and an emptied apartment or a vacation absence does not reliably clear an infestation.

Foods Some Roaches Refuse

Diet is not only about what roaches will eat. Some populations have evolved to reject a specific sugar used in baits.

Research published in *Science* in 2013 by North Carolina State University entomologists showed that in glucose-averse German cockroaches, glucose stimulates the bitter-sensing taste cells as well as the sugar-sensing ones, so a bait sweetened with glucose tastes bitter to them. A 2023 study in the *Journal of Economic Entomology* found the trait in populations worldwide and showed that glucose-containing baits also weaken the secondary kill described above, because glucose-averse nymphs eat less of the contaminated feces.

If bait is going untouched while roaches remain active, the fix is usually a product with both a different active ingredient and different food ingredients. Our guide to how to tell if roach bait is working covers the timeline and the signs to check before switching.

What This Means for Cleaning and Baiting

  1. Degrease, do not just sweep. Grease films behind and under the range and refrigerator are a durable food source that a broom never touches.
  2. Deny water first. Fix leaks, dry sinks and dish racks at night, insulate sweating pipes, and empty pet bowls. Water is the resource roaches can least afford to lose.
  3. Use rigid containers with tight lids for cereal, flour, sugar, and pet food. Original cardboard and paper packaging protects nothing and adds harborage.
  4. Take out trash on a schedule and clean the can itself, not only the bag.
  5. Vacuum droppings and debris, ideally with a HEPA filter, since droppings are both food for nymphs and an aggregation cue for other roaches.
  6. Make bait the best food available. Texas A&M AgriLife Extension notes that baits are most effective when few food alternatives are present, and recommends many small pea-sized placements near harborage rather than a few large ones, kept fresh and replaced when dried out.
  7. Keep sprays and cleaners off bait placements. Cockroaches avoid contaminated bait.

Place bait where children and pets cannot reach it, or use enclosed stations, and follow the product label for sites, amounts, and precautions. For the full treatment sequence, see how to get rid of roaches. For how roaches locate food in the first place, see how roaches find food.

When To Call a Professional

  • Roaches are ignoring bait after two to three weeks, which Texas A&M treats as the point to switch to a different active ingredient.
  • You see roaches in the open during the day, which usually means a large population.
  • You live in a multi-unit building, where treating one unit is rarely enough.
  • Someone in the home has asthma or a cockroach allergy, since droppings, cast skins, and body parts are documented allergens and asthma triggers.
  • You have cleaned thoroughly and consistently and the population is not declining.

Frequently Asked Questions

Can roaches live without any food?

For a period, yes, and how long depends on conditions rather than on a single number. The 2026 Journal of Economic Entomology survival study found that German cockroaches survived longest at lower temperatures, that higher humidity extended survival when no resources were available, and that food access mattered most at higher humidity. Penn State reports a month without food for oriental cockroaches when water is available.

What is a roach's favorite food?

There is no single favorite. Extension sources describe a preference for starches, sweets, grease, and meat products, and research shows German cockroaches actively balance protein against carbohydrate depending on life stage. Some populations actively reject glucose, so even "sweet" is not a safe generalization.

Do roaches eat their own droppings?

Yes, and young nymphs depend on it. First instars can develop into second instars on adult feces alone, acquiring gut microbes along with nutrients. This is also how insecticide from bait moves through a population, producing secondary and tertiary kill.

Can roaches chew through plastic containers?

We found no reliable research supporting claims that cockroaches chew through rigid plastic food containers. They do get into loose bags, thin film packaging, and boxes that are not fully sealed, and food odor escaping from poorly closed packaging is enough to bring them. Rigid containers with tight-fitting lids, or glass and metal, solve the practical problem regardless.

Do roaches eat wood or fabric?

Not as a preferred food, but UF/IFAS lists cloth, paper, leather, and book bindings among materials American cockroaches have been observed eating. They are after the starch, protein, and cellulose, plus any food residue on the surface. Cockroaches are not structural wood destroyers the way termites are.

Will starving roaches make them leave?

Not reliably, and it can make them more mobile rather than gone. Texas A&M notes that when food and water are scarce, cockroaches must search farther each night, which actually increases their contact with baits and traps. Sanitation is valuable because it improves treatment, not because it evicts an established population on its own.

Do roaches eat other insects?

Yes. Dead insects appear in the extension diet lists for both German and American cockroaches, and field-collected cockroaches have been found with arthropod cuticle in their guts. They are scavengers rather than active predators, and they are prey themselves for a long list of animals covered in our guide to what eats roaches.

Sources

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