Adult. The potato leafhopper, Empoasca fabae, is a member of the leafhopper family Cicadellidae and order Hemiptera. This leafhopper adult is bright, limey green and about 1/8 inches long (3 mm). The body is wedge-like with a broad head and a tapered abdomen (Fig. 1). The head has short antennae, big, white eyes, and six white spots behind the eyes. The wings are clear and extend past the end of the abdomen. Also, there are prominent spines on the hind legs. Adults are easily disturbed and will attempt to jump or fly away when approached.
Egg. Potato leafhopper eggs are cylindrical and translucent to pale green. Eggs are less than a millimeter long.
Nymph. Immature potato leafhoppers develop through five instars before becoming adults. First instars are pale but gradually gain more green color as they mature. Nymphs also start to develop wing pads after the third instar (Fig. 2). Nymphs are easily disturbed and will attempt to walk away sideways or backwards when approached.
Biology and Ecology
Potato leafhopper is native to North America and commonly found throughout the U.S. This pest also feeds on a wide host range, including alfalfa, soybean, potato, clovers, apples, and beans. Potato leafhoppers do not overwinter in Iowa, but migrate here annually with southerly winds in May (Fig. 3). Often their presence in field crops is noted in late June or July. After field crops have senesced in the late summer, potato leafhoppers will move to wild plants and feed until frost.
Females deposit eggs inside plant stems or leaves for about 30 days. Eggs hatch after a week and nymphs start feeding externally on the undersides of leaves. The time it takes to develop from egg to adult is dependent on weather, but ranges from 9-18 days. There are 3-4 generations per year in Iowa.
Injury and Damage
Adults and nymphs have piercing-sucking mouthparts, and feed on the sap within plant phloem. Unlike other leafhoppers, this species repeatedly probes host plants and lacerates cells. While feeding, potato leafhoppers inject a watery saliva that includes an enzyme that reduces plant photosynthate movement. Yield loss occurs through reductions in intermodal length and stem height, and decreases in crude protein content.
Initial feeding injury can result in discoloration, sometimes called “hopperburn” that shows up as v-shaped yellowing on leaf tips (Fig. 4). Plants can also be covered with sugar-rich honeydew, and result in shiny and sticky plants. Sometimes potato leafhopper feeding injury is misdiagnosed with herbicide injury or nutritional deficiencies. Prolonged feeding will cause wrinkling, cupping, and stunting. Eventually, leaf tips can turn brown and fall off the plant (Fig. 5). Moisture-stressed fields can magnify the feeding injury from potato leafhopper.
Scouting and Management
Potato leafhopper is one of the most economically important alfalfa pests in Iowa (Fig. 6). Scout for this pest after the first cutting since migrations to Iowa typically happen during the second growth. Also, first-year alfalfa fields should be monitored closely, as they tend to be more susceptible to potato leafhopper injury. Potato leafhopper is an occasional soybean pest and is most often noticed in early-vegetative fields (Fig. 7). Severe infestations are often associated with fields located near alfalfa fields.
For small plants, look for potato leafhopper adults and nymphs on the undersides of leaves. Look at 20 sequential plants in at least five areas of the fields; estimate the number of hoppers per plant. For plants taller than six inches, use a sweep net (15-inch diameter) to collect leafhoppers. Take 20 sweeps in at least five areas of the field; estimate the number of hoppers per sweep. Also take note of any plant damage and honeydew in the field. If economic thresholds are reached within seven days of a planned harvest, early harvest is recommended instead of a foliar insecticide.
Economic thresholds in alfalfa are based on leafhopper density, plant height, market value and control costs. As market value of hay increases, the economic threshold decreases. Conversely, as control costs or plant height increases, the economic threshold also increases.
Table 1. Dynamic economic threshold values for potato leafhopper based on plant height, market value, and control costs. Table adapted from Tooker (2013).
Economic thresholds in soybean are based on leafhopper density and plant height (Krupke 2016). For vegetative soybean, treat when leafhoppers exceed two per plant. For flowering fields, treat when leafhoppers exceed one per trifoliate leaf. During pod and seed set (R3-R6), treat when leafhoppers exceed two per trifoliate leaf.
Cultural and Biological Control in Alfalfa
1. Alfalfa-oat mixtures tend to have fewer potato leafhoppers than pure alfalfa stands.
2. Pubescent, or hairy, varieties tend to be more tolerant to leafhopper feeding than glabrous (smooth) plants. Glandular-haired alfalfa causes greater mortality and reproduced reproduction compared to smooth-stemmed alfalfa. Regardless of variety selection, first-year alfalfa stands are considered susceptible to potato leafhopper.
3. Many natural enemies will feed on potato leafhopper adults and nymphs, including lady beetles, predatory bugs, and lacewings. Because these pests are mobile, aphids are preferred prey if co-infesting plants.
Chasen, Dietrich, Backus and Cullen. 2014. Potato leafhopper ecology and IPM focused on alfalfa. JIPM.
Krupke. 2016. Soybean insect control recommendations. Purdue Extension.
Tooker. 2013. Potato leafhopper in alfalfa. Penn State Extension.