“Potato bug” is a common name applied to at least three very different creatures: the Colorado potato beetle, the Jerusalem cricket, and the pillbug (roly-poly). Each one eats completely different foods, so the answer depends on which insect you’re looking at. Here’s what each one feeds on and why it matters for your garden.
Which Insect Are You Looking At?
None of these insects are actually true bugs in the scientific sense, but the name “potato bug” gets used for all of them. The Colorado potato beetle is a small, round, yellow-and-black striped beetle found on garden plants. The Jerusalem cricket is a large, wingless, soil-dwelling insect with a big orange head and black-and-white banded abdomen, reaching about 35 to 50 mm long. The pillbug is the small gray armored critter that rolls into a ball when disturbed. Knowing which one you have tells you exactly what it’s eating and whether you need to worry.
Colorado Potato Beetle Diet
The Colorado potato beetle is the one most gardeners are actually dealing with. Potatoes are its preferred host plant, but it feeds on a wide range of plants in the nightshade family: tomatoes, eggplant, peppers (rarely), ground cherry, tobacco, and several weedy nightshades like horse-nettle and buffalo-bur. Buffalo-bur was actually its first recorded host plant before it discovered cultivated potatoes. Both adults and larvae chew through leaves, and the beetle can adjust its diet to whatever nightshade species are locally abundant. Feeding on non-nightshade plants has been documented but is rare enough that those plants aren’t considered normal hosts.
The real damage comes from the larvae. The oldest larvae, in their fourth and final stage before pupating, are responsible for roughly 75% of all feeding damage. They can strip leaves down to bare stems surprisingly fast. Potato plants can tolerate up to 30% leaf loss before flowering without a significant yield hit. But once tubers start forming underground, that tolerance drops sharply to about 10% defoliation. This is why timing matters so much: the same amount of chewing that’s harmless in early spring can devastate your harvest later in the season.
Jerusalem Cricket Diet
Jerusalem crickets are omnivores with a split schedule. During the day, they stay underground and feed on roots, tubers, and decaying plant material. At night, especially after rain, they come to the surface to hunt live insects and scavenge animal matter and plant debris. This underground feeding on tubers like carrots and potatoes is exactly how they earned the “potato bug” nickname.
Despite their alarming appearance, Jerusalem crickets are generally less of a garden threat than Colorado potato beetles. They’re solitary creatures that don’t form large populations, so the damage they cause tends to be scattered. You’ll most often encounter them when digging in soil or turning over rocks and logs. If you find bite marks on underground root vegetables, a Jerusalem cricket may be the culprit, but widespread crop loss from these insects is uncommon.
Pillbug Diet
Pillbugs are primarily decomposers. Their main food source is decaying plant leaves, fallen mulch, and other dead organic material. They live under mulch, leaf litter, and rocks, breaking down dead vegetation and recycling nutrients back into the soil. In most gardens, they’re beneficial.
That said, pillbugs occasionally cross the line into pest territory. They’ve been found feeding on seedlings, plant roots, and the fruit of low-growing crops. Documented targets include tomato, radish, lettuce, mustard, pea, bean, and cucumber plants. The damage is usually minor and happens most often in gardens with heavy mulch or very moist conditions, where pillbug populations boom and run out of their preferred decaying material to eat.
Protecting Your Garden From Colorado Potato Beetles
Since Colorado potato beetles cause the most significant crop damage of the three, they deserve the most attention. Several natural predators help keep populations in check, including green lacewings, predatory stink bugs (particularly the spined soldier bug), and generalist spiders. A naturally occurring fungus has been shown to reduce beetle populations by up to 75% under the right conditions, and a tiny parasitic wasp can destroy 71 to 91% of beetle eggs laid on eggplant.
Crop rotation is one of the simplest defenses. Adult beetles overwinter in the soil near where they fed the previous year. If you move your potatoes, tomatoes, and eggplant to a different part of the garden each season, emerging beetles have to travel farther to find food, and many won’t make it. Hand-picking adults and larvae off plants works well in small gardens, especially if you target the younger larvae before they reach the destructive fourth stage. Checking the undersides of leaves for clusters of bright orange-yellow eggs and crushing them early can prevent most of the damage before it starts.
For Jerusalem crickets and pillbugs, management is rarely necessary. Reducing excess moisture and clearing debris near vulnerable seedlings discourages pillbugs from feeding on live plants. Jerusalem crickets are best left alone unless you’re finding consistent tuber damage, in which case simply relocating them away from root vegetables is enough.