The term “potato bug” causes significant confusion because it is used to describe two distinctly different insects in various regions, leading to misidentification and ineffective control attempts. The common name can refer to a highly destructive agricultural pest or a large, intimidating but mostly harmless burrowing insect. Correctly identifying the specific insect responsible for damage is the first step toward successful plant management and determining whether intervention is necessary.
Resolving the Identity Crisis
The two creatures most often called “potato bugs” are the Colorado Potato Beetle (CPB) and the Jerusalem Cricket. The Colorado Potato Beetle (Leptinotarsa decemlineata) is a true beetle and the major agricultural pest of the two. This insect is easily recognized by its oval, dome-shaped body, measuring about three-eighths of an inch long, featuring a yellowish-white body with ten distinct black stripes running lengthwise down its wing covers. Its larvae are reddish-orange with a humped back and two prominent rows of black spots along the sides.
The Jerusalem Cricket (Stenopelmatus fuscus or talpa), also known as the “child of the earth,” is a large, wingless orthopteran. This insect can grow up to two inches long and possesses a robust, stout body with a disproportionately large, rounded head. Its powerful mandibles are used primarily for burrowing and feeding on roots, giving it an intimidating appearance.
The Jerusalem Cricket is not venomous and is generally shy, choosing to retreat rather than confront humans. It only bites defensively if roughly handled, resulting in moderate but temporary pain. While it can feed on tubers and roots, it is not a significant agricultural pest and poses no threat to human health. The Colorado Potato Beetle, however, is a serious threat to nightshade crops and requires active management.
The Life Cycle and Damage of the True Pest
The Colorado Potato Beetle (CPB) is the true garden pest, characterized by rapid reproduction and voracious feeding habits. Adults spend the winter burrowed in the soil, emerging in early spring when potato shoots appear. After feeding, females begin laying clusters of bright yellowish-orange eggs, often 20 to 30 at a time, on the underside of host plant leaves. A single female can lay between 350 to 800 eggs over five weeks, quickly establishing a large population.
The eggs hatch within four to nine days, releasing tiny larvae that immediately begin feeding. The larvae progress through four distinct growth stages, or instars, over two to four weeks. The final stages cause the most significant plant damage, with the fourth instar larvae responsible for up to 75% of the total foliage consumption. Once fully grown, the larvae drop from the plant and burrow into the soil to pupate, a stage that lasts approximately five to ten days.
New adults emerge from the soil to feed and reproduce, leading to a second, and sometimes a third, generation within a single growing season. Both the adults and the larvae feed aggressively on the foliage of plants in the nightshade family, which includes potatoes, tomatoes, and eggplant. This feeding results in severe defoliation, where the leaves are skeletonized or completely consumed. Unchecked infestations quickly destroy a plant’s ability to photosynthesize, leading to reduced tuber size and yield loss, particularly if defoliation occurs during the flowering period.
Managing Potato Bug Infestations
Effective management of the Colorado Potato Beetle requires a targeted, multi-faceted approach centered on disrupting its life cycle. For small gardens, non-chemical methods like hand-picking are highly effective, especially when targeting overwintering adults in the spring and egg clusters on leaf undersides. Collected insects and egg masses should be dropped into a container of soapy water for their immediate demise. Crop rotation is also a foundational strategy, as moving susceptible crops at least one-quarter mile away from the previous year’s location reduces the number of emerging adults that find the new plants.
Cultural practices can also help, such as applying a thick layer of straw mulch to deter adults from laying eggs by making the soil surface less accessible. Adjusting planting times to either very early or very late helps plants avoid the peak activity of the first generation of beetles. When populations are large or non-chemical methods are insufficient, gardeners may use targeted biological controls.
The bacterium Bacillus thuringiensis var. tenebrionis (Bt) is a specific biological agent effective only against the young larval stages of the beetle. Another option is the use of insecticides containing spinosad, an organic-approved compound that targets small larvae, though careful timing is necessary for maximum effectiveness. For the Jerusalem Cricket, the best course of action is non-intervention, as they are not a significant pest and contribute to the ecosystem. If found inside a home, the Jerusalem Cricket should be relocated outdoors.