Empoasca fabae
Potato leafhopper (PLH) does not overwinter in MA, but arrives annually in the spring carried by storm winds traveling from the south. They have a broad host range, but prefer certain crops such as potatoes and legumes. Because low numbers of adults or nymphs cause injury that reduces yield, it is important to protect plants before adult numbers are high and before nymphs build up. Left uncontrolled, PLH populations will continue to grow rapidly.
Identification
It is easy to overlook potato leafhoppers (PLH) in the crop, as they are small and well hidden.
- Eggs are tiny, light-colored, and deposited into plant tissue, making them very difficult to locate.
- Nymphs usually feed on the underside of leaves and are bright green, wedge-shaped and fast-moving. They tend to move sideways, in a crab-like fashion.
- Adults are about 1/4-inch long, light yellow-green, and fly up from foliage when it is disturbed or shaken—they look like tiny green sparks flying away from the plants. Aster leafhopper adults resemble PLH but are a more drab olive green in contrast to the light green of PLH adults.
Life Cycle
PLH overwinters in the southern US. The adults migrate north on storm winds annually in spring, arriving in New England from early to mid-June. Once adults arrive, they lay eggs in the veins and petioles of leaves. Nymphs hatch after about 10 days. Presence of nymphs indicates an established population. Two or more generations may occur after adults arrive, until killed by frost.
Damage
PLH feeds on a broad range of plants, though certain groups such as legumes are favored. In vegetables, they are primarily a pest of potatoes and snap or dry beans, but can also affect eggplant and other vegetables. They additionally affect fruits including raspberries and apples and field crops including alfalfa, cowpea, soybean, clover, sunflower, and tobacco. Mowing nearby field crops can cause PLH populations to soar in vegetable crops as adults are disturbed and seek new hosts. Weeds including smartweed, pigweed, shepherd's purse, and carpetweed can also support PLH, and even trees such as maples, oaks, and elms can be hosts.
Adults and nymphs feed by inserting their needle-like beak into the plant and sucking out the sugary phloem sap. During feeding, they also inject a toxic enzyme into the plant, causing a condition known as hopperburn. The toxin increases plant respiration, decreases photosynthesis, and disrupts the vascular tissues which carry the products of photosynthesis to other parts of the plant. Symptoms of hopperburn include yellowing, browning, and curling of leaves, typically beginning at leaf tips and margins. Symptoms usually do not extend past yellowing and curling of leaf margins in some crops such as eggplant, but in crops such as potatoes and peas, leaf margins can quickly turn brown and brittle, and untreated infestations can eventually result in a significant portion of the foliage drying up. Symptoms of hopperburn can easily be mistaken for disease symptoms.
Plant injury and yield loss can be significant, and feeding can reduce yield before damage is visible. In potato, yield loss occurs even before the development of obvious symptoms. Damage can be severe on early-season and red varieties of potato, as well as in green beans (especially when they are infested prior to flowering), eggplant and raspberries. Long-season cultivars tend to be more tolerant. Beans are more susceptible when they are young than at later stages.
Monitoring & Thresholds
Because low numbers of adults or nymphs cause injury and reduce yield, it is important to protect plants before adult numbers are high and before nymphs build up. Left uncontrolled, potato leafhopper will continue to build up. It is difficult to count adults since they fly quickly when foliage is shaken or disturbed. Sweep nets can be used to detect adults. Once nymphs develop, they can be monitored by visually inspecting lower leaf surfaces on lower leaves.
- In potatoes, treat at a threshold of 1 adult per sweep net (if you see one adult per plant when you shake the foliage, you are in that range) or 15 nymphs per 30 leaves.
- For seedling beans, use a threshold of 2 adults per row foot. For beans in the 3rd-leaf to bud stage, use a threshold of 5 adults per row foot or 1 nymph per leaflet.
- In eggplant, use a threshold of 1.5 adults or large nymphs per leaf.
Cultural Controls
- Crop varieties: Early-season and red varieties of potato tend to suffer more damage than long-season varieties; varieties that are less susceptible include Katahdin, Russet Burbank, Russet Norkota, Ontario, and Red la Soda.
- Row cover can be used to delay infestation in snap beans until flowering, when plants are less susceptible to damage. Using row cover is recommended on young eggplant, as it protects from flea beetles, Colorado potato beetle and potato leafhopper.
Chemical Controls & Pesticides
Refer to the New England Vegetable Management Guide for lists of registered products in potato, eggplant, and beans. Follow all label instructions to facilitate safety and efficacy of chemical controls.
In potato and eggplant, some materials registered for Colorado potato beetle (CPB) adults will also control leafhopper, including neonicotinoid foliar sprays. These and several other carbamate, synthetic pyrethroid, and organophosphate products are also registered for leafhopper in potato, eggplant, and snap beans, for which a single application is often sufficient.
For organic growers, pyrethrin has been shown to be the most effective product for reducing leafhopper numbers and damage. Because pyrethrin is a contact insecticide, good coverage is important, especially of the leaf underside where nymphs are found. Pyrethrin products break down quickly in sunlight, so the residual period is short. Spraying late in the day or in the evening may provide better control than spraying early in the morning. Products containing azadirachtin have also demonstrated efficacy against leafhoppers (especially in fruit systems) and could be used in tank-mixes or in rotation with pyrethrin.
Pollinators and other beneficials
Although bees do not forage extensively in beans or potatoes, they may be active in the field when these crops or the weeds within the crop fields are flowering. During that time, selection of products with lower toxicity to bees is advised. Look for toxicity information on the label, and also in the New England Vegetable Management Guide Table 27, and in the products listed for each crop and pest. Although many conventional insecticides with active ingredients listed above have high toxicity to bees, there are variations within classes, e.g. acetamiprid has a lower toxicity to bees (rated as 'medium') compared to most other neonicotinoids. Sivanto (flupyradifurone) is a new product in a novel class of chemistries, the butenolides, that works against sucking pests, including PLH. It is also labeled for CPB control. This new active ingredient is being touted as an alternative to neonicotinoids, and has been given a bee toxicity rating of Low.
For conservation of both native pollinators and honeybees, control weeds in the crop and avoid drift onto flowering borders or crops. However, encouraging some flowering areas in the margins is good for supporting pollinators before and after crops bloom. These can also be a nursery and refuge for beneficial predators and parasites of insect pests.
Crops that are affected by this insect:
Resources include: Vegetable Insect Management by Rick Foster and Brian. R. Flood, 2005; Handbook of Vegetable Pests by John L. Capinera, 2001.