Variation in adult populations of the potato leafhopper (Homoptera: Cicadellidae) and feeding injury among clones of red maple

Leaf flush phenology of red maple, Acer rubrum L., changes in the number of potato leafhopper adults, Empoasca fabae (Harris), and feeding injury were recorded for 2 yr for 5 different maple clones. Migratory adults started arriving between late April and early May. More insects were collected from clone 56026 than from the other 4 clones during this time. Populations peaked during 31 May-14 June. During that peak, more insects were collected from clones 60068, 56026, and 59904 than from clones 55410 and 57775. Leafhopper numbers declined thereafter. Leaf flushing (i.e., leaf growth initiation, expansion, and development) differed among clones during April. Clone 55410 was the Ist clone to show signs of leaf flushing. The order of leaf flushing from early to late was 55410 with more leaves than 57775, both followed by 59904, which in turn had more leaves than 60068 or 56026. Leaf flushing of clone 56026 occurred late in the spring. Clone 56026 suffered the most feeding injury during the growing seasons and clone 57775 showed the least feeding injury. During spring, the cumulative number of leafhoppers collected on traps was negatively correlated with the amount of leaf flushing and positively correlated with the amount of foliage injury. That is, trees with more unexpanded and young leaves had more leafhoppers and, thus, showed more feeding injury. Late in the season, the amount of feeding injury was positively correlated with the cumulative number of insects caught on traps. Early in the season, amount of feeding injury was, in part, influenced by the degree of leaf flushing. However, other tree factors appear to influence degree of feeding later in the season.