Potato leafhoppers were first observed in the last week of May in potato in the Connecticut Valley and in beans in central/southeastern MA – an early arrival, not surprising for this season. It is likely their arrival in these crops is widespread and scouting is warranted.
Adults are about 1/4 inch long, light yellow-green, and fly up from foliage when it is disturbed or shaken. These are the first arrivals. PLH overwinters in the southern US and moves north annually. Nymphs will be found later on the underside of leaves, light green, wedge-shaped and very fast-moving. Damage can be severe on early-season varieties of potato and red potatoes, as well as in green beans. Beans are more susceptible when they are young than at later stages. Eggplant is also susceptible. Field crops such as alfalfa, clover, soybean, sunflower and tobacco are also hosts.
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 margins turn brown and brittle first, followed by death of entire leaves, a condition known as ‘hopperburn.’ In eggplant, leaf margins and tips turn yellow and curl up. Feeding can reduce yield before damage is visible.
It is important to protect plants when leafhoppers first arrive, before nymphs 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 – treat if more than 1 adult is found per sweep. If you see several when you shake the foliage, you are probably in that range. Once nymphs develop, they can be monitored by visually inspecting lower leaf surfaces on lower leaves. Treat if more than 15 nymphs are found per 50 leaves. University of Connecticut has established a threshold of 1.5 leafhopper per leaf in eggplant. In potato and eggplant, some materials registered for Colorado potato beetle adults will also control leafhopper, including neonic foliar sprays such as Provado. These and several other carbamate, synthetic pyrethroid and organophosphate products are also registered for leafhopper in potato, eggplant and snap beans. Refer to the New England Vegetable Management Guide for registered products.
On organic farms, pyrethrin (PyGanic EC5.0) has been shown to be the most effective product for reducing leafhopper numbers and damage. 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. Don’t wait for numbers to build up. Row cover can be used to delay PLH infestation in snap beans until flowering, when plants are less susceptible to damage.
Although bees do not forage extensively in beans or potatoes, if the crops or weeds within the crop field are flowering, bees may be active in the field, and selection of products with lower toxicity to bees is advised. See Table 20 in the Vegetable Guide for bee toxicity ratings. While the classes of insecticides listed above tend to have high toxicity to bees, there are variations within classes; for example, neonics are considered very toxic in general, but Assail (acetameprid) is much less so.
For conservation of both native pollinators and honeybees, clean cultivation and drift prevention are both important. However, encouraging some flowering areas in the margins is good for supporting pollinators before and after crops bloom. These can also be refugia for other beneficials (as well as pests like Tarnished plant bug).