1 U.S. National Arboretum, Floral and Nursery Plants Research Unit, U.S. Department of Agriculture, Agricultural Research Service, 10300 Baltimore Avenue, BARC-West, Building 010A, Room 238, Beltsville, MD 20705-2350
2 U.S. National Arboretum, Floral and Nursery Plants Research Unit, U.S. Department of Agriculture, Agricultural Research Service, 11601 Old Pond Drive, Glenn Dale, MD 20769
The suitability of container-grown clones of red maple, Acer rubrum L., as a host to the potato leafhopper, Empoasca fabae Harris (Homoptera: Cicadellidae), under different fertilization regimes was determined, and compared to different freeman maple cultivars (A. ×freemanii E. Murray). Three clonal selections of red maple (USNA numbers 56026, 59904, and 55410), and three freeman maple cultivars (55892 `Indian Summer', 67256 `Jeffersred' [trademark Autumn Blaze], and 55890 `Armstrong') were potted in 7.6-L containers, fertilized with either 0, 3.3, or 6.6 g/pot of calcium nitrate and used in experiments. When given a choice, female leafhoppers laid more eggs on leaves of red maple clone 56026 than on leaves of clone 59904, with oviposition linearly increasing on both clones with increases in the fertilization level applied to the trees. Yet, when female leafhoppers were confined to leaves using organza sleeve cages, oviposition increased linearly as fertilizer level increased, without a significant clonal effect. Oviposition did not differ among freeman maple cultivars, nor was it influenced by the fertilizer level applied to the freeman maple trees. Nymphs had the lowest odds of surviving to adulthood when reared on the freeman maple `Jeffersred', but highest when reared on red maple 59904. Red maple 59904 had the fastest growth rate while red maple 55410 had the slowest. Leaf initiation and expansion in red maple 56026 was significantly slower than in the other selections. Leaf development of these three red maple clones was significantly accelerated by the application of fertilizer, regardless of level. The maple selections differed in their mean amounts of foliar macronutrients and micronutrients, which related to the fertilizer level applied to trees. Unfertilized trees had the highest C to N ratio, which decreased as fertilizer level applied to trees was increased. This study showed that fertilization improved the performance of the potato leafhopper on previously nonpreferred maple selections, and that the foliar nutrient content and C to N ratio could be used as indicators of tree susceptibility to insect attack under different growing conditions.
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