. Bird populations in east central Illinois : fluctuations, variations, and development over a half-century. Bird populations. Fluctuations from Year to Year 27 Vegetation Important for interpretation of fluctuations in bird populations from year to year is the time sequence in the destruction of elm trees that took place throughout the region. Within the city limits of Champaign-Urbana, the first mortality of trees was observed in 1944, when the American elm became infected with a mycoplasm- like organism that is spread by a leafhopper (Scaphoideus luteolus Van D.). This produces a phloem nec
. Bird populations in east central Illinois : fluctuations, variations, and development over a half-century. Bird populations. Fluctuations from Year to Year 27 Vegetation Important for interpretation of fluctuations in bird populations from year to year is the time sequence in the destruction of elm trees that took place throughout the region. Within the city limits of Champaign-Urbana, the first mortality of trees was observed in 1944, when the American elm became infected with a mycoplasm- like organism that is spread by a leafhopper (Scaphoideus luteolus Van D.). This produces a phloem necrosis. Dutch elm disesase, caused by a fungus (Ceratocystis ulmi (Buism.) C.) and carried by a native bark bettle {Hylurgopinus rufipes Eichh.) and a Euro- pean bark beetle (Scolytus multistriatus Marsh.) began to kill trees in 1951. All native elm species may be infected with the disease, but the American elm is most susceptible. Both diseases spread rapidly during the 1950s (Fig. 7). By 1961, more than 99% 100 90 80 70 ^ 60 *» 50 ^ 40 30 20 10 1—r-r t—r. Total f Dutch elm disease '-—" Phloem necrosis j I i i i i I i i i i 1945 1950 1955 I960 1965 Fig. 7. Cumulative percentages of the original elm tree population in Urbana- Champaign lost through diseases (Carter and Carter, 1974). of all elm trees were dead (Carter and Carter, 1974). In William Trelease Woods, scattered dead elm trees were first noticed in 1953, they became very conspicuous in 1954, and it was evident. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Kendeigh, S. Charles (Samuel Charles), 1904-. Champaign : University of Illinois Press
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