ACT Reading Practice Test 48

NATURAL SCIENCE: This passage discusses a disease that is detrimental to certain trees in North America.

One of the greatest concerns of landscapers is tree disease. Ash trees are among the most common trees in North America, and they are also very susceptible to disease and decline.

Line 5 One cause of decline in ash trees is ash yellows. This disease infects mainly white and green ash in the Northern United States. Ash yellows is caused by a phytoplasma: virus-like pathogens that are spread by insects. Ash yellows leads to a gradual decline

10 in tree health for about two to ten years before the tree dies. Some common symptoms include short internodes and tufting of foliage at branch ends, pale green or pale yellow leaves, defoliation, and a sparse canopy. Cankers may also form on the branches and trunk.

15 Unsightly “witches’ broom” sprouts might appear on the branches, but it is more common for them to appear on the trunk. The trunk may also develop cracks if the tree is infected with ash yellows. Rarely does an ash tree recover from ash yellows. Experts guess that this

20 disease is more common than most homeowners realize because witches’ brooms and yellowing are not always visible on the infected trees. Sometimes cankers and cracks are the only signs of the disease. The term ash decline is used to refer to a tree with

25 more than one condition. Ash decline may involve the ash yellows disease or another problem called verticillium wilt. Ash decline is often used to describe any decline in health that is unexplainable. Ash decline involves branch tip death, defoliation, and a slow

30 decline over a number of years. Trees with ash decline may appear to recover in the spring and decline again in July and August. Verticillium wilt on ash can also result in cankers and dieback similar to ash yellows. Trying to diagnose

35 a tree is difficult because symptoms could be caused by a variety of problems. Sick ash trees may suffer from verticillium wilt, ash yellows, environmental stress, or a combination of these ailments. Ash yellows has been a known disease in the

40 United States since the 1930s. However, the disease was not distinguished from general ash decline involving environmental factors until the 1980s. In the last eighty years, North America has seen a significant decline in some of its ash trees.

45 No single factor has been proven to cause ash decline. Ash yellows and environmental factors may work together to create ash decline. Studies show that ash yellows is often detected where environmental factors like water shortage or insect damage are present.

50 A survey of several Midwestern states found that some ash decline was found to be independent of ash yellows. The droughts in the 1980s may have caused the decline of ash trees in the Midwest. Cold winter temperatures may also play a role in decline.

55 Ash trees are important in the ecology of North American forests. The decline of these trees may have a severe impact on the health of other plant and animal communities. Green ash provides nesting sites for several species of birds and other wild creatures. Insects

60 and fish flourish in the cool waters made possible by the shade of ash trees. Green and white ash are also very popular in landscaping. Their decline could result in reduced property values. Ash trees also represent a valuable hardwood

65 resource. An estimated 275 million feet of ash lumber is harvested annually. In the Northeastern United States, about 33 percent of the commercial forest area includes ash trees. There are no known cures for the diseases

70 mentioned. Experts recommend removing very sick trees while keeping healthy trees well watered and fertilized. Dead limbs should also be removed to maintain the health of ash trees.