Silkworms eat mulberry leaves. That’s not just a preference: after thousands of years of domestication, the silkworm (Bombyx mori) has become one of the most specialized eaters in the insect world, feeding almost exclusively on fresh leaves from the white mulberry tree (Morus alba). In lab studies, larvae that were given food other than mulberry could not survive through their final growth stage. If you don’t have access to a mulberry tree, artificial diets made from dried mulberry powder can work as a substitute, though they come with some trade-offs.
Why Mulberry Leaves Are Essential
Silkworms are classified as monophagous, meaning they eat one thing. Over centuries of selective breeding for silk production, they’ve lost the ability to thrive on anything else. Fresh mulberry leaves provide the specific balance of protein, sugars, and moisture that silkworm larvae need to grow through all five of their larval stages (called instars) and spin a quality cocoon.
White mulberry (Morus alba) is the standard species used in sericulture worldwide. Other mulberry species, like red mulberry (Morus rubra), can also be fed to silkworms, but white mulberry is the most widely available and well-studied option. If you have a mulberry tree nearby, that’s your best and cheapest food source.
Picking and Storing Fresh Leaves
Harvest leaves that are green, intact, and free of spots or discoloration. Younger, tender leaves near the tips of branches are best for small, early-stage worms. Older, larger leaves work well for later instars when the larvae eat in much greater volume.
Freshness matters. Wilted or dried-out leaves lose nutritional value quickly. If you need to store picked leaves, keep them in a sealed plastic bag in the refrigerator. Research on mulberry leaf storage shows that more than 40% of key nutrients can drop significantly when leaves sit at room temperature in open air. Vacuum-sealed storage preserves nutrients best, but for home raisers, a zip-lock bag with a damp paper towel in the fridge will keep leaves usable for several days. Wash leaves gently before feeding and pat them dry, since excess water droplets can drown tiny hatchlings.
Pesticide Contamination Is a Serious Risk
Silkworms are extraordinarily sensitive to pesticides. Common neonicotinoid insecticides like imidacloprid and thiamethoxam are lethal to silkworms at concentrations far below what’s used on crops. In one study, the lethal dose for imidacloprid was just 0.33 mg per liter, a tiny fraction of the 47 to 93 mg per liter typically sprayed on agricultural fields. Even sublethal exposure slows growth, reduces body weight, lowers pupation rates, and damages silk quality.
This means you should never collect mulberry leaves from trees near agricultural fields, roadsides with herbicide use, or gardens where pesticides have been applied. If you’re unsure about a tree’s history, leaves from an untreated backyard tree or a purchased mulberry plant are safer choices. Fungicides like tebuconazole also harm silkworms, so any chemical treatment on or near the tree is a concern.
Artificial Diets as a Backup
If you can’t get fresh mulberry leaves, commercially available silkworm chow is the alternative. These artificial diets are typically sold as a dry powder or block that you rehydrate and prepare at home. A straightforward recipe used in research combines mulberry leaf powder and soybean flour in a 1:1 ratio, though commercial products may include additional ingredients to boost nutrition.
Once prepared, artificial diet firms up to a soft, cheese-like texture. You feed it to the worms by grating thin layers directly over them using the smallest holes on a standard cheese grater. This works especially well for tiny hatchlings that can’t chew through thick pieces of food.
Artificial diets do come with measurable downsides. Silkworms raised on them take roughly 12 to 13% longer to develop through their larval stages compared to those eating fresh leaves. Cocoon shell quality, which reflects how efficiently the worm converts food into silk, also tends to be lower on artificial diets. For classroom projects or small hobby batches, these differences are minor. For anyone trying to produce quality silk, fresh mulberry leaves are clearly superior.
Feeding Hatchlings and Early Instars
Newly hatched silkworms are tiny, about the size of an eyelash, and need their food delivered in very small pieces. If you’re using fresh leaves, chop or shred them into thin strips no wider than the worms themselves. If you’re using artificial diet, grate a thin layer directly over the hatchlings in their container, covering the entire surface area so every worm has food within reach.
During the first two instars (roughly the first week), feeding twice a day is generally sufficient. The worms are small, eat slowly, and don’t consume much. Keep food fresh by removing dried-out leaf pieces before adding new ones. Leftover food that stays moist too long can develop mold, which is harmful to the larvae.
Feeding Later Instars
Appetite increases dramatically from the third instar onward. By the fifth and final instar, silkworms are eating machines, consuming several times their body weight in leaves before they stop eating and begin spinning their cocoon. Research on feeding frequency shows that three to five feedings per day, spaced four to five hours apart, produce the best growth and cocoon outcomes for these later stages.
At this point, you can offer whole mulberry leaves rather than chopped pieces. Lay fresh leaves directly on top of the worms. They’ll crawl up and feed from the underside. Replace uneaten leaves once they begin to dry out or wilt. During their final instar, a batch of several dozen worms can go through a surprising volume of leaves daily, so plan your leaf supply ahead of time.
What Not to Feed Silkworms
Silkworms cannot survive on lettuce, cabbage, spinach, or other common greens. While very young larvae may nibble on certain alternative leaves out of hunger, they will not complete development on anything other than mulberry or a mulberry-based artificial diet. Some online sources suggest alternatives like osage orange leaves (from a related plant family), but these are unreliable for full development and should only be considered as a very short-term emergency option, not a replacement.
Avoid feeding any leaves that are yellowed, spotted with fungus, or visibly damaged by other insects. Contaminated or decaying plant material introduces bacteria and pathogens into the rearing container. Keep the feeding environment clean by removing frass (droppings) and old leaf debris every day or two, especially in later instars when waste accumulates quickly.