2. Hemlock is a hallmark of southern Appalachia's national parks.

　　3. The invasive insect, known as the hemlock woolly adelgid (HWA), is from Japan.

　　4. The key to killing the HWA is to catch it early and act quickly.

　　5. An infected tree usually dies immediately.

　　6. The Hemlock in the U.S. will be saved from HWA soon.

　　7. The long term, best way to control the pests HWA is spraying.

　　8. Since 1951 the HWA has spread to more than________.

　　9. Releasing one species of non-native bug to kill another could create________.

　　10. It will take several different insects operating year-round to________.