which trees die through removing known infested trees and treating trees with insecticides can allow local governments more time to plan, remove, and replace trees that would eventually die. This strategy saves money as it would cost $10.7 billion in urban areas of 25 states over 10 years, while removing and replacing all ash trees in these same areas at once would cost $25 billion (with another estimate putting the removal alone at $20–60 billion). Some urban areas such as Minneapolis have large amounts of ash with slightly more than 20% of their urban forest as ash. Monitoring In areas where emerald ash borer has not yet been detected, surveys are used to monitor for new infestations. Visual surveys are used to find ash trees displaying emerald ash borer damage, and traps with colors attractive to emerald ash borer, such as purple or green, are hung in trees as part of a monitoring program. These traps can also have volatile pheromones applied to them that attract primarily males. Sometimes trees are girdled to act as trap trees to monitor for emerald ash borer. The stressed tree attracts egg-laying females in the spring, and trees can be debarked in the fall to search for larvae. If detected, an area is often placed under a quarantine to prevent infested wood material from causing new infestations. Further control measures are then taken within the area to slow population growth by reducing beetle numbers, preventing them from reaching reproductive maturity and dispersing, and reducing the abundance of ash trees. Government agencies in both the U.S. and Canada have utilized a native species of parasitoid wasp, Cerceris fumipennis, as a means of detecting areas to which emerald ash borer has spread. The females of these wasps hunt other jewel beetles and emerald ash borer if it is present. The wasps stun the beetles and carry them back to their burrows in the ground where they are stored until the wasps’ eggs hatch and the wasp larvae feed on the beetles. Volunteers catch the wasps as they return to their burrows carrying the beetles to determine whether emerald ash borer is present. This methodology is known as biological surveillance, as opposed to biological control, because it does not appear that the wasps have a significant negative impact on emerald ash borer populations. Management In areas where emerald ash borer is non-native and invasive, quarantines, infested tree