Potato Leafhopper on Vegetables

Appearance

• Eggs: Transparent to pale yellow, tiny, inserted into leaf tissue.
• Nymphs: 5 instars, most of which are elongated and wedge-shaped, pale green, smaller versions of adults, but without wings. Nymphs are very active, crawling sideways like crabs when disturbed.
• Adults: Pale green, about 1/8" long, elongated wedge-shaped, gradually tapering to hind end, and bug-eyed. Adults fly quickly away when disturbed.

Life cycle/habits

• Adults overwinter in warmer climates and arrive in Maryland on warm fronts in spring.
• After mating, eggs are inserted into petioles or veins of leaf undersides.
• Nymphs and adults are typically found on leaf undersides, inserting mouthparts, sucking out sap, and then secreting a toxin back into the leaf.
• Up to six generations a year.
• In the fall, adults are carried southward again by cold fronts.

Host plants

• Potato and bean (mainly snap bean), eggplant, and over 200 other plants including cucumber, pumpkin, rhubarb, squash and sweet potato. Favors legumes such as alfalfa and bean in early season, and potato later in the summer.

Signs/symptoms

• Feeding creates light dots on leaves called stipples, and foliage may yellow and become stunted.
• Hoppers also secrete a toxin into leaves as they feed, causing a distinctive set of symptoms known as hopperburn: leaf tips and margins curl upward, turn yellow to brown, and become brittle; leaves appear as if singed by fire. The toxin is not systemic, so damage is proportional to insect numbers.
• Plants may become stunted.
• Severe leaf damage and premature plant death is common in potato, whereas leaf discoloration and curling are more characteristic on bean.

Monitoring

• First, inspect for young nymphs, which can crawl but cannot fly. Later, tap affected plants and watch for many quick-flying, tiny, pale green insects.
• Monitor with yellow sticky traps.
• Watch for stippled or bleached leaves. Leaf tips and edges may curl or distort, yellow, and turn brown.

Prevention/control

• Egg-laying can be foiled with row cover. 
• Parasitoids and general predators (ants, spiders, ladybugs, lacewings) actively reduce numbers.
• For large numbers, use botanical insecticides such as insecticidal soap, horticultural oil, neem, pyrethrum, or combinations thereof. Spray early in the day when insects are sluggish. Thoroughly wet leaf undersides. Apply repeatedly for large populations.
• Dusting plants with diatomaceous earth may help.
• Leaf hairiness has been shown to deter leafhoppers. Select hairy varieties.
• Keep weeds down, especially perennial weeds that harbor leafhopper eggs.