The term “potato bug” often causes confusion, as it refers to two distinct types of creatures: an insect that feeds on plants and a crustacean that consumes decaying matter. Understanding these distinctions is important for identifying their feeding habits and impact.
Understanding “Potato Bug” Identity
The common term “potato bug” refers to two distinct types of creatures: the Colorado potato beetle (scientific name: Leptinotarsa decemlineata) and terrestrial crustaceans known as pillbugs and sowbugs (order Oniscidea). The Colorado potato beetle is a true insect, known for its distinctive appearance. Adults are oval-shaped, about 3/8 inch long, with yellow-orange bodies and ten black stripes running lengthwise on their wing covers.
Pillbugs and sowbugs, in contrast, are not insects but are land-dwelling crustaceans, making them more closely related to crabs and shrimp. These creatures are dark gray, have seven pairs of legs, and possess a segmented, armored body. A key visual difference is that pillbugs can roll into a tight ball when disturbed, a behavior that earns them the nickname “roly-polies,” while sowbugs cannot.
What Colorado Potato Beetles Eat
The Colorado potato beetle primarily feeds on plants in the Solanaceae family, also known as nightshades. Preferred food sources include potatoes, eggplants, and peppers. They also consume tomatoes, petunias, or tobacco.
Both adult Colorado potato beetles and their larvae are voracious eaters. Adult beetles emerge in spring and begin feeding on host plants, with females laying yellowish-orange eggs on the undersides of leaves. Once hatched, the red and black larvae immediately start consuming plant foliage. Larval stages are responsible for the majority of feeding damage.
What Pillbugs and Sowbugs Eat
Pillbugs and sowbugs are primarily detritivores, meaning their diet consists mainly of decaying organic matter. They play a role in decomposition, feeding on materials like rotting wood, decaying leaves, and other dead plant material. These crustaceans also consume fungi and bacteria found on decomposing vegetation.
While their primary food source is decaying matter, pillbugs and sowbugs can feed on live plant material. This happens when populations are high or preferred food sources are scarce. They might nibble on tender seedlings, new roots, lower leaves, or soft fruits and vegetables in direct contact with damp soil. Damage from pillbugs and sowbugs is minor and often resembles slug damage, appearing as ragged holes.
Impact on Host Plants
The feeding habits of the Colorado potato beetle can significantly impact host plants, especially potatoes. Both adult beetles and their larvae consume leaves, leading to defoliation. This damage can range from minor chewing to complete stripping of foliage, a process known as skeletonization.
Significant defoliation reduces the plant’s ability to perform photosynthesis, leading to reduced plant vigor, stunted growth, and yield losses in agricultural settings. If left unchecked, heavy infestations can cause plant death. In contrast, pillbugs and sowbugs can cause minor damage to tender plants or ripe fruits touching the soil. However, their impact is less severe and widespread than that of the Colorado potato beetle, and they are often considered beneficial decomposers in garden ecosystems.