The potato plant provides a rich food source for a variety of insect pests, requiring constant vigilance from growers. From emergence until harvest, both the foliage and underground tubers are vulnerable to attack. Managing these insect populations is necessary to ensure the plant sustains the photosynthetic activity required for a healthy, marketable yield. Recognizing and responding to the presence of these insects is key to preventing crop decimation.
Key Pests That Attack Potato Plants
The Colorado Potato Beetle (Leptinotarsa decemlineata) is the most destructive pest of potato foliage, with both adult and larval stages causing significant damage. The adult is distinct, featuring a round, yellowish-orange body with ten black stripes on its wing covers, measuring about 10 millimeters long. Females lay clusters of bright, yellowish-orange eggs, usually in batches of about 30, on the underside of leaves. These hatch into reddish-brown, humpbacked larvae with two rows of dark spots. The larvae, especially the older stages, are responsible for up to 75% of the feeding damage, consuming leaves until they are skeletonized, which severely stunts the plant and reduces tuber growth.
The Potato Leafhopper (Empoasca fabae) is a small, pale-green, wedge-shaped insect, measuring about 3 millimeters long. In northern regions, this pest migrates north on wind currents each spring, arriving to infest plants in early summer. Both adults and wingless nymphs feed by inserting needle-like mouthparts into the leaf tissue and sucking out plant fluids, often on the underside of leaves. While feeding, the leafhopper injects a toxin that causes “hopperburn.” This damage starts as a yellowing or browning of the leaf tips and margins, which then curl upward, leading to the death of the leaf and substantial yield loss.
Flea beetles, such as the Potato Flea Beetle (Epitrix cucumeris), are tiny, dark, metallic-colored insects named for their habit of jumping quickly when disturbed. Adult flea beetles feed on foliage, chewing small, round holes that give the leaves a “shot-hole” appearance. While adult damage is generally minor, the larvae live in the soil and feed on the potato tubers. The larvae are small, slender, white grubs with a brown head. Larval feeding creates small brown tunnels and a pimpled surface on the tubers, which reduces their marketability and storage life.
Non-Chemical Control Strategies
Crop rotation is an effective cultural practice that interrupts pest life cycles. Adult Colorado Potato Beetles and flea beetles overwinter in the soil of the previous year’s field. Moving the potato crop to a new location forces emerging adults to travel farther for a food source, often reducing the initial infestation level. This technique works well against pests with limited mobility after emerging.
Physical control methods offer immediate results without introducing chemical substances. Handpicking adult Colorado Potato Beetles and their larvae into soapy water is practical for small-scale operations, especially early in the season. Floating row covers create a physical barrier over emerging plants, preventing overwintered adult beetles from accessing foliage to feed and lay eggs. The covers must be removed when the plants begin to flower to allow for pollination.
Hilling involves mounding soil up around the base of the plant stem as it grows. While primarily done to protect developing tubers from light, hilling also buries Colorado Potato Beetle eggs and larvae that fall to the ground to pupate, disrupting their life cycle. Maintaining optimal plant health through proper watering and fertilization increases the plant’s natural resistance to feeding damage. Companion plants, such as marigolds, can also attract beneficial insects like ladybugs and parasitic wasps that prey on pest eggs and larvae.
Chemical and Targeted Pest Management
When non-chemical methods fail, targeted treatments should focus on biological options before synthetic chemicals. _Bacillus thuringiensis_ (Bt) is a naturally occurring soil bacterium used as a microbial insecticide. Specific strains, such as Bt var. tenebrionis, are toxic to the larvae of beetles like the Colorado Potato Beetle. The insect must ingest the toxin, which disrupts its digestive system, causing it to stop feeding and die. Bt is harmless to humans and most non-target insects. Applying Bt when larvae are small and actively feeding is necessary for maximum effectiveness, as older larvae are more resistant.
Synthetic insecticides are categorized by how they interact with the plant and the pest. Contact insecticides kill the pest upon direct exposure, requiring thorough coverage of the plant’s surface, including the undersides of leaves where pests hide. Systemic insecticides are absorbed by the plant, moving through its vascular system to make the entire plant toxic to feeding pests. Systemics are a better option for insects with piercing-sucking mouthparts, such as the Potato Leafhopper.
Effective chemical control relies on timing the application to coincide with the pest’s most vulnerable life stage, such as newly hatched larvae. Growers must carefully follow label instructions to ensure the correct dosage and application interval, which prevents the development of insecticide-resistant populations. Integrating these chemical tools with cultural practices is known as Integrated Pest Management (IPM). IPM ensures that synthetic controls are used only as a last resort to manage severe outbreaks, minimizing environmental impact.