'Hopperburn' refers to the complex of symptoms associated with potato leafhopper (PLH) feeding injury. This leafhopper, native to North America, has a broad host plant range including 220 plant species in 26 families. Though, most of its host plants are in the legume family. Crops primarily attacked by the potato leafhopper include potato, beans, soybeans and alfalfa. Other host plants include eggplant, cucumber, Jerusalem artichokes, squash, sweet potato and rhubarb. Reports also note PLH on hops and hemp. PLH arrives every summer in June from southern locations where they overwinter in pine forests. They complete two or more generations in Connecticut before non-reproductive adults are transported back by prevailing winds to the south in the fall. Environmental conditions can have a significant impact on this insect, beginning with their inability to survive our winter temperatures. On the other hand, warmer conditions increase the severity of infestation during summer and drought can worsen its feeding damage.
Adult leafhoppers insert their eggs into plant stems and nymphs will emerge 7-14 days with warmer temperatures inducing an earlier emergence. Nymphs cannot fly but they do walk rather rapidly over the plant surface. Nymphs have a peculiar way of moving sideways which helps in spotting who they are. Nymphs develop through five instars eventually molting into adults that can migrate long distances aided by wind currents. Adults are small (1/8 of an inch or about 3 mm), bright green and with six white spots behind the eyes on top of the head. Adults and nymphs feed on plants using 'pierce-sucking' mouthparts, probing and damaging tissues while they inject saliva into the tissues as they feed resulting in their hallmark 'hopperburn' damage.
This type of plant damage presents general symptoms like tip-wilting in young plants, yellowing or chlorosis that expands through the leaf and plant stunting. Other specific symptoms include triangular yellowing at the leaf tips of alfalfa and some clovers. In potato, soybean and beans the leaves exhibit yellowing at the margins, leaf curling and eventual leaf tissue death and leaf drop. The damage progression from initial symptoms to death of leaves may take only 4-5 days, depending on the leafhopper infestation level, degree of feeding and plant moisture stress. In potatoes, nymphs can cause more feeding damage than adults. To some, hopperburn appears like leaf senescing or drought damage so it is important to inspect the plants for leafhopper presence.
Potato leafhopper feeding damage on green beans. Damage starts with cupping and/or curling followed by discoloration in curled region and tissue death. This damage is known as 'hopperburn'. Leaf in photos was exposed to 4 potato leafhopper adults in a controlled setting. Photos: Bivek Bhusal, UConn
Monitoring is essential to detect the leafhoppers before extensive damage occurs and to evaluate if a damaging pest population is present. Check the underside of leaves for nymphs and adults can be flushed out of foliage by shaking the plants. Insect sweep nets can be used to collect insects for counting. Action thresholds are available to make decisions about treatment needs. See the New England Vegetable Management Guide for crop-specific action thresholds and registered control products. Other management tactics include row covers for beans and eggplants and using varieties that are less susceptible to the leafhopper. For instance, potato varieties noted to be moderately resistant to leafhoppers include Katahdin, Elba and All Red while Russet Burbank is least susceptible to hopperburn.
