Urban forests across the country are facing very serious threats due to several types of tree-killing pests. At a meeting I attended last week with the Sustainable Urban Forests Coalition, Faith Campbell, senior policy representative at the Nature Conservancy, discussed these threats and the urgent need for our country to step up our game on detecting, suppressing, and preventing the spread of these invasive insects that are harming our urban forests.

Why are urban forests at risks?

Cities are often where some of our worst tree-killing pests arrive and spread. With the number of people living in cities, moving in and out of cities and shipping things in and out of cities, there are many opportunities for these pests to sneak their way into new areas. Often, these pests have arrived into port cities by way of wood pallets on shipping cargo — where the bugs often lie hidden from sight until it is too late. They can also come from plants that are shipped from other areas for landscaping yards and beautifying homes. Then, there is the issue of firewood. When people transport firewood from one location to another (both from rural areas and urban environments), they are often unknowingly transporting these unwelcomed pests with them.

Often, it is not the adult insects that directly harm the tree — it is their larvae. Adults lay their eggs in the tree and as the larvae grow and emerge, they damage the phloem and xylem of the tree, which are responsible for nutrient and water transport, causing the tree to wilt and eventually die.

What are some of the major tree-killing pests of concern and what do you need to know?

Emerald ash borer
Emerald ash borer. Credit: Howard Russell, Michigan State University, Bugwood.org

a. Help spot it! The adult EAB is a metallic green, about half an inch long and has a flattened back. It has purple abdominal segments under its wing covers. The EAB can fit on the head of a penny.

b. What’s at risk? The EAB attacks ash trees.

c. Where is it now? EAB has been found in Illinois, Indiana, Iowa, Kentucky, Maryland, Michigan, Minnesota, Missouri, New York, Ohio, Pennsylvania, Tennessee, Virginia, West Virginia, and Wisconsin.

Asian Longhorned Beetle
Asian longhorned beetle. Credit: U.S. Department of Agriculture

a. Help Spot it! The adult ALB is one to one and a half inches long. It’s a black, shiny, bullet-shaped beetle with white spots and exceptionally long antennae that are banded with black and white.

b. What’s at risk? The ALB attacks a variety of tree species, including birch, horse chestnut, poplar, willow, elm, and ash, and maple. That’s right; our maple syrup industry is at risk!

c. Where is it now? Illinois, New Jersey, and New York.

Goldspotted oak borer
Goldspotted oak borer. Credit: Center for Invasive Species Research

a. Help Spot it! The adult GSOB is a small, bullet-shaped beetle about 10 millimeters (half an inch) long and has six golden yellow spots on its dark green forewings.

b. What’s at risk? GSOB attacks have been found in older, mature trees of three types of oak.

c. Where are the areas of concern? Southern part of California.

What can you do?

If you believe that you have spotted one of these pests, try to collect an adult beetle so a positive determination can be made. Then contact a person in your state at either: