Potato leafhopper (Empoasca fabae) is primarily a pest of potatoes and snap beans, but can also affect eggplant and lettuce. Potato leahoppers overwinter in the Gulf Coast states and move north in spring, arriving in New England around mid-June. It is easy to overlook them in the crop, as they are small and well hidden. Adults are about 1/4 inch long, light yellow-green, and fly up from foliage when it is disturbed or shaken. Nymphs are found on the underside of leaves, light green, wedge-shaped and very fast-moving. They tend to move sidewise, crab-like, on the leaf surface. Damage can be severe. Early-season and red varieties of potato tend to suffer more damage than long-season varieties. Green beans are very susceptible, especially when they are infested early in their growth. Low numbers of leafhoppers can cause a lot of damage.
Adults and nymphs feed by inserting a needle-like beak into the plant and sucking out sap. They also inject a toxin into the plant, which causes yellowing, browning, and curling of leaves. In potato, leaf veins turn yellow, then leaf margins turn brown and brittle, followed by death of entire leaves. In beans the leaf turns mottled brown as if infected with a disease before dying completely. Both adults and nymphs cause damage. Plant injury and yield loss can be significant.
It is important to protect plants before nymphs build up. In potato, adults can be sampled using a sweep net, by shaking the plants, or by observing the underside of leaves. A widely used threshold based on sweep netting is one adult per sweep. It’s not clear how that translates to what is observed by scouting plants directly. If nymphs reach one per three leaves, treat. (These are compound leaves.) University of Connecticut has established a threshold of 1.5 leafhopper per leaf in eggplant.
In potato, some materials registered for Colorado potato beetle adults will also control leafhopper, including neonicotinoids. Other carbamate, synthetic pyrethroid and organophosphate products are also registered. Often a single application is sufficient. Refer to the New England Vegetable Management Guide for recommended materials.
For organic potato growers, pyrethrin (PyGanic EC5.0) has been shown to be relatively effective in reducing leafhopper numbers, especially nymphs. Good coverage is important. The residual period is short. Spraying late in the day or in the evening may provide better control than spraying early in the morning.
For Current information on production methods (including varieties, spacing, seeding, and fertility), weed, disease, and insect management, please visit the New England Vegetable Management Guide website.