Leafhoppers damage leaves by sucking out the liquid contents of cells. The potato leafhopper usually shows up in June on Long Island. It can be found on leaf undersides and moves sideways when disturbed. Damage appears as a marginal yellowing of the leaf. The grape leafhopper is similar in appearance, but has 3 black spots and does not move sideways.
Damage appears as a yellow speckling, especially along veins.
Growers do not usually treat for leafhoppers. Aphids , another group of sucking insects, are a common pest on many plants. In some years, the dark brown grapevine aphid has literally blanketed shoot tips of vines. Usually, grapes are sufficiently vigorous to tolerate attack and treatment is not necessary. Finally, the European red mite has become a concern for Long Island grapegrowers.