Environmental threat to ash wood The emerald ash borer, an exotic beetle imported accidentally from Asia, has killed more than 50 million white ash trees in the eastern United States and now threatens groves in New York's Adirondack Mountains that are used to make baseball Global temperature rise likely allows the beetle to survive in what was once too cold Regulations In the American major leagues, Rule 1.10(a) states: The bat shall be a smooth, round stick not more than 2.61 inches in diameter at the thickest part and not more than 42 inches in length. The bat shall be one piece of solid wood. Bats are not allowed to be hollowed or corked—that is, filled with an alien substance such as cork which reduces the weight. This corking is thought to increase bat speed without greatly reducing hitting power, though this idea was challenged as unlikely on the Discovery Channel series MythBusters. Both wooden and metal alloy (generally aluminum) bats are generally permitted in amateur baseball. Metal alloy bats are generally regarded as being capable of hitting a ball faster and farther with the same power. However, increasing numbers of "wooden bat leagues" have emerged in recent years, reflecting a trend back to wood over safety concerns and, in the case of collegiate summer baseball wood-bat leagues, to better prepare players for the professional leagues that require wood bats. Metal alloy bats can send a ball towards an unprotected pitcher's head up to away at a velocity far too high for the pitcher to get out of the way in time. Some amateur baseball organizations enforce bat manufacturing and testing standards which attempt to limit maximum ball speed for wood and non-wood bats. In high school baseball in the United States: The bat is not permitted to be more than in diameter in proximity to width and length. Its "drop" (inches of length minus ounces of weight) must be no more than 3: for example, a 34 inch (863.6‑mm) bat must weigh at least . The bat may consist of any safe solid uniform material; the National Federation of State High School Associations rules state only "wood or non-wood" material. To be legally used in a game, an aluminum bat has to be a BBCOR (Batted Ball Coefficient of Restitution) bat because it has been determined that a pitcher loses the ability to protect himself when this ratio is