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The emerald ash borer is a threat to Indiana's 150 million ash trees. (Photo courtesy Department of Forestry and Natural Resources) |
High stakes
While vector-borne viruses pose a threat to public health, insect pests can be equally damaging to other urban “residents.”
Pests are just one of the hazards that endanger trees and shrubs, which provide a wide range of benefits to the urban environment. In the past few years, urban pest control has become even more challenging as an increasing number of invasive species defoliate and kill millions of trees. Often, these pests have no natural predators, because many of them are not native to North America. Instead, they are imported here from other continents, arriving in packing materials and shipping crates.
"Urban communities are sometimes more susceptible to pests like the Asian longhorn beetle or emerald ash borer,” says Purdue Extension urban forester Rita McKenzie. And the aftermath can be devastating. “Beetles can take out a nine- or 10-block area of trees. The emerald ash borer has killed more than 6 million ash trees in the Detroit area alone,” says McKenzie of the pest that is a threat to some 150 million ash trees in Indiana . “That's what can happen if you have a monoculture. Urban areas need to have a diversity of trees.”
Taking stock
Helping establish or maintain diversity so the urban landscape won't be completely decimated by a pest invasion or disease is just one of the services provided by Purdue Extension's urban foresters. However, before cities and towns can achieve some level of diversity, they must first find out what trees they have and what condition they're in. Purdue's Department of Forestry and Natural Resources aids cities and towns with this process. Teams of students, led by faculty advisors, compile street tree inventories and conduct workshops on proper tree care and selection. The street tree inventory work is funded through Indiana Department of Natural Resources urban forestry conservation grants, which are awarded to help communities develop long-term tree management programs that will improve the urban environment.
"The street tree inventory establishes a baseline,” McKenzie says. “You have to know what you have before you can manage it. If you have 50 percent of one type of tree, such as silver maple, which many cities and towns were planting in the 1950s, you don't want to plant any more silver maples.”
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Concrete, high-rise buildings and pollution can threaten the survival of trees. Purdue Extension's urban foresters help Indiana communities inventory, select and care for trees, which provide a wide range of environmental benefits. (Photo courtesy Indianapolis Convention & Visitors Association) |
This was the case in Fowler, a small town in the northwestern part of the state. “We knew we had a lot of maples, but we wanted to find out what else we had,” says Amy Bott, Fowler's director of community development. “And we wanted to find out what the condition of our trees was and what our priorities should be. The inventory confirmed that we had a high percentage of maples and shouldn't plant any more. But it also identified some utility and tree conflicts, as well as potential planting sites for new trees.”
With inventory in hand, town officials applied for a second urban forestry grant to fund a management plan, which was completed this winter. “In the meantime, we continued doing routine maintenance and pruning,” Bott says. “Now, with the management plan, we have a blueprint to manage and prioritize, as well as plant new trees when funding allows.”
In this era of escalating budget cuts, a street tree inventory can provide the basis for financial analysis that can justify the cost-benefits of both maintaining existing trees and planting new ones. “Knowing what you have and what the benefits are is important before you go in front of the city council and ask for funding for tree maintenance or more trees. It's more cost-effective for cities to plant trees than to cut them down,” McKenzie says, citing reduced cooling costs, storm sewer runoff, and carbon dioxide and other air pollutants among the many benefits of trees.
But the urban environment does not always cooperate. “Heat coming off concrete buildings, a wind tunnel effect on a street, soil composed of fill materials—these are just some of the things that trees have to tolerate,” McKenzie says. “It requires quite a bit of work to get trees to thrive in an urban area. And unlike a forest that is managed as an entity, urban trees need to be managed on an individual basis—one tree at a time.”
Purdue's urban pest management and urban forestry programs draw on the expertise of researchers and Purdue Extension specialists in entomology, forestry and natural resources, horticulture, botany and plant pathology, the Plant and Pest Diagnostic Laboratory, and Purdue Pesticide Programs and collaborate with state and federal agencies. These programs and services demonstrate that Purdue Agriculture's commitment extends well beyond the farm, providing the research and education that safeguards Indiana's urban communities as well.
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