The potato plant, a member of the nightshade family, is a globally important food source, but it is susceptible to numerous insect pests that target its dense foliage and underground tubers. These pests attack the plant at every stage of growth, dramatically reducing yield and quality. Effective management requires quickly and accurately identifying the specific pest, as different organisms need distinct control strategies. Understanding the characteristic signs of infestation is the first step toward protecting the potato crop.
Identifying the Primary Foliage and Stem Pests
Pests that feed directly on the leaves and stems cause rapid defoliation and hinder photosynthesis. The Colorado Potato Beetle (Leptinotarsa decemlineata) is perhaps the most notorious of these, causing significant damage in both its adult and larval stages. Adults are distinctive, oval-shaped beetles about half an inch long, featuring bright yellow and black stripes on their wing covers. Females lay clusters of 10 to 30 bright yellow-orange eggs on the underside of potato leaves.
The larvae are the most destructive stage, appearing hump-backed and ranging from reddish-orange to salmon pink, marked with two rows of black spots. These larvae are voracious eaters, often starting on new foliage tips and skeletonizing leaves until only the veins remain. Heavy populations can completely defoliate a plant, significantly impacting yield once tubers begin to bulk.
The Potato Flea Beetle (Epitrix spp.) is a common pest, a tiny insect about 1.7 to 2.2 millimeters long, appearing black or metallic greenish-brown. When disturbed, these beetles jump rapidly, giving them their name. Their feeding leaves characteristic small, circular holes in the leaves, resulting in a “shot-hole” appearance. While adult feeding damage usually does not reduce yield, it serves as an important warning sign of their presence.
The Potato Leafhopper (Empoasca fabae) is a migratory pest that arrives annually from southern regions, presenting as a small, light green, wedge-shaped insect. Both the adults and the nymphs, which move sideways, possess piercing-sucking mouthparts. While feeding, these pests inject a toxic saliva that blocks the plant’s vascular tissue, causing a specific symptom known as “hopperburn.” Hopperburn first appears as a triangular yellowing or browning at the leaf tips and margins, which then curls upward.
Detecting Pests That Damage Potato Tubers
Pests that reside below ground are often not discovered until harvest. Wireworms, the larvae of click beetles, are persistent soil-dwelling pests that can live in the soil for three to five years. These larvae are hard-bodied, slender, and cylindrical, with a shiny, yellowish-brown appearance. Wireworms damage tubers by boring small, round holes on the surface that lead to narrow, shallow tunnels into the flesh.
Slugs and snails target developing tubers, especially in heavy or moist soils. Unlike the narrow tunneling of wireworms, slugs create irregular-shaped holes on the tuber surface that often extend into large, hollowed-out cavities. Above ground, glistening slime trails left on the soil surface or lower leaves indicate a slug infestation. Damage from both pests severely reduces the market quality of harvested potatoes.
The Potato Tuber Moth (Phthorimaea operculella) attacks both the foliage and the tubers. The small, greyish-brown adult moth lays eggs on exposed tubers or through soil cracks, allowing the larvae to enter. Once inside, the pale greenish larvae tunnel beneath the skin, often near the eyes. Piles of frass, or droppings, near the tunnel entrances indicate a tuber moth infestation.
Comprehensive Strategies for Pest Control
Managing potato pests requires combining multiple tactics. Cultural controls are the foundation of this strategy, beginning with crop rotation, which is effective against pests with multi-year life cycles like wireworms. Avoiding planting potatoes in fields recently in sod or grass can significantly reduce wireworm populations. Hilling, the practice of mounding soil around the growing stems, prevents the Potato Tuber Moth from reaching the tubers, as the female moths cannot lay eggs on deeply buried potatoes.
Mechanical and physical controls reduce pests, especially in smaller plots. Handpicking controls the slow-moving adult and larval stages of the Colorado Potato Beetle, particularly as overwintering adults emerge in the spring. Floating row covers, applied immediately after planting, exclude Potato Flea Beetle and Potato Leafhopper adults, preventing them from laying eggs or feeding on the foliage. This physical barrier is most useful early in the season.
Organic and biological controls use specific, naturally derived products. The bacterium Bacillus thuringiensis var. tenebrionis (Bt) controls Colorado Potato Beetle larvae. It must be applied when the larvae are small, as the toxins destroy the insect’s gut tissue upon ingestion. For soft-bodied insects like the Potato Leafhopper, products containing Neem oil (azadirachtin) disrupt development and deter feeding. Soil-dwelling pests like wireworms can be managed using entomopathogenic nematodes, such as Steinernema carpocapsae and Heterorhabditis bacteriophora, which are microscopic roundworms that parasitize and kill the larvae.