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SHSAT English Language Arts Quiz

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ELA: READING COMPREHENSION

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The Copper Leaf Blight of Corrin Valley (1) In the summer of 1953, apple growers in Corrin Valley began to notice something wrong with their trees. Leaves curled at the edges and turned a dull copper color, starting at the tips and working inward. Affected trees produced small, hard apples that few buyers would accept, and many trees died within four or five years. Over the next decade, at least four researchers or groups offered competing explanations for what growers came to call "copper leaf." (2) The earliest explanation came from Aldo Mott, the county's orchard inspector. In 1954 he argued that a hard frost in April 1953, which struck just as the trees were blooming, had injured the young wood. To test his idea, Mott compared trees on the valley floor, where cold air settles on still nights, with trees on the surrounding hillsides. He found the blight far more often on low ground, and he told growers to plant all new trees on the hillsides. In 1956 the Corrin Growers' Association adopted his explanation and called on members to burn oil heaters in low-lying orchards on cold spring nights. (3) Meanwhile, the association wanted to learn how far the problem had spread. In 1955 it mailed a questionnaire to its members and announced that the blight had reached nearly 300 of the valley's 640 orchards. Newspapers repeated the figure for years, and it convinced many families that the valley's apple industry was finished. (4) Dr. Mirela Tash, who directed the plant disease laboratory at the Hollis Agricultural Station, proposed a soil fungus in 1958. She pointed out that the valley floor was not only colder but also wetter, and fungi thrive in damp soil. From letters sent to the station, Tash had first estimated that about 200 orchards were affected. Before beginning her experiment, however, the Hollis staff went to every orchard in the valley and found the blight in 112 of them. The 1955 survey's figure of nearly 300, they explained, had counted any orchard with browned leaves, including many that had only ordinary apple scab. The station then replaced the soil around thirty young trees with steam-sterilized soil. Within two seasons, nineteen of the thirty showed copper leaf, about the same rate as untreated trees nearby. Tash did find fungus in the roots of dying trees, but she concluded that it had moved in after the trees weakened rather than causing the disease. (5) The frost explanation was losing support. The spring of 1959 was unusually cold, and growers who kept their heaters burning all season still lost trees. In 1960 Jorun Ostby, a grower who led the valley's fruit cooperative, suggested that the trees lacked boron, a mineral they need in small amounts. The cooperative urged members to spray boron on their trees, and Ostby sprayed fifty trees in her own orchard while leaving fifty unsprayed. After a year, the two groups looked the same. (6) In 1961 Dr. Ilse Varga, an insect specialist at Pellam College downriver, proposed with her students that a tiny leafhopper was carrying a bacterium from tree to tree. Growers soon began calling Varga and her students the Pellam team. Leafhoppers gather in low, sheltered ground, which explained the pattern Mott had seen. Varga's group wrapped twenty-four trees in fine mesh netting for two summers and left twenty-four neighboring trees uncovered. Only two of the netted trees developed the blight, compared with fifteen of the uncovered ones. The group also found the bacterium in the insects' salivary glands, a result that Tash's laboratory confirmed the next year. (7) By 1963 the association's confirmed count of affected orchards had risen from 112 to about 150. That year the association dropped the frost explanation and accepted the findings of the Pellam team. Instead of heaters, it now advised removing infected trees and spraying for leafhoppers. By 1968 only nine orchards in the valley still reported copper leaf.

According to the passage, what did the researchers whose findings the growers' association accepted in 1963 discover?

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