Understanding Emerald Ash Borer

Agrilus planipennis

Overview of EAB

The Emerald Ash Borer (EAB) has killed millions of ash trees since its discovery in southeastern Michigan in 2002. Native to Asia, this insect was probably introduced to the United States in wood packing material carried in on cargo ships or airplanes. Through a combination of natural spread and human activity it is now found in Michigan, Ohio, Indiana, Illinois, Missouri, Pennsylvania, Maryland, West Virginia, Virginia, Wisconsin, and now Minnesota, placing millions of additional ash trees at risk.

Symptoms of EAB

Adult beetles feed on leaves and it is uncertain what impact adult feeding has on tree health. Larvae on the other hand feed on the inner bark and disrupt the movement of water and minerals within a tree causing eventual dieback, decline and death of the tree. Symptoms of early infestations may be difficult to diagnose. Be on the lookout for multiple declining ash in a given area. As infestation progresses, small vertical splits in the bark can be seen on twigs or trunk and woodpecker holes may be present on trees. Trees may die after 2-4 years or less (small trees).

crown dieback Typically the top 1/3 of the tree crown dies first and works its way down the tree Trees appear to lose about 30%-50% of their canopy after 2 years of infestation.

suckers on infested tree As the top of the tree continues to decline epicormic shoots form Epicormic shoots can arise at the interface between healthy and dead tissue anywhere in the canopy Dense root sprouting may occur after death of a tree

galleries under bark Distinct “S” shaped frass filled larval galleries that score the outer sapwood and phloem underneath the bark Galleries in an affected area can range from 4- 20 inches in length Galleries from an individual larvae become progressively wider as the larvae grows

D-shaped exit hole D-shaped exit holes Exit holes are generally present after an infestation has been present for 1 yr. or more Approximately 1/8 inch in diameter

 

Signs of EAB

Adults

• Usually bronze or golden green with dark metallic emerald green wing covers
• Adults are slender and can be 1/4 inch to 1/2 inch in length
• Top of the abdomen under the wings is metallic purplish red (seen when wings are spread)
• Adults may be difficult to detect even in areas of high infestation as they are very small
• Short period of activity (3-6 weeks of activity)
• Generally active during the day (sunny and warm days) Adults will hang out in bark crevices or on foliage during rain, heavy cloud cover, high winds, or when temps reach above 90 F.
• Adults can be found most years beginning from late May into Mid-August
• Peak Mid to Late June

Larvae

• Slender, flattened, segmented (10 total abdomen segments) cream colored larvae with a brown head can be found by peeling back loose bark on infested trees
• Larvae range in size from 1 -1 1/4 inches in length
• Pincer-like appendage on the last segment
• Larvae hatch from eggs deposited in bark crevices
• Larvae chew through the bark and begin feeding on phloem
• Feeding is completed in autumn and pre-pupal larvae over winter in the outer sapwood or bark.
• Pupation begins in late April or May
• Newly formed adults will often remain in pupal chamber for 1-2 weeks prior to emergence in late May into Mid-August
• Some larvae may require a second year of maturation feeding prior to emerging the following year as adults

Host Trees (listed from most susceptible to less susceptible): Green Ash Fraxinus pennsylvanica Black Ash F. nigra White Ash F. americana Blue Ash F. quadrangulata

Distinguishing EAB from Similar Species

- All will be attacked if beetle populations are high enough - Some evidence to suggest that green ash may be preferred over other species EAB can infest ash trees as small as 1” DBH up to the largest specimen trees Stress may contribute to the vulnerability and speed that a tree declines from EAB EAB has also killed seemingly vigorous trees growing under optimum conditions (especially as beetle densities build)

EAB has distinct features, but it can be confused with the following beetles: o Banded Ash Borer o Japanese Beetle o Six- Spotted Tiger Beetle o Bronze Birch Borer o Two-lined Chestnut Borer o Caterpillar Hunter More information can be found at: http://www.forestpests.org

 

Management Strategy

The most critical strategy is easy, DO NOT move firewood. The most common source of EAB spread has been through the transportation of wood products.

The best protection from the EAB is prevention. Individual, high value trees at risk for infestation by EAB can be treated preventively with soil applications of the insecticide, Xytect. A soil drench in the fall or early spring will provide season long protection. Both preventive treatments and theraputic options are availabe. An evaluation by a certified arborist will determine the best treatment option for your tree.

Rainbow Treecare can help:

Rainbow Treecare is nationally known for having developed the standard of protection for Dutch elm disease, likewise RTC has been developing EAB treatment strategies for prevention of EAB. Our latest research with the Ohio State University, completed in 2008, has resulted in the new standards in preventing EAB.

Here is how Rainbow Treecare is helping locally in Minnesota:

• Our 45 certified arborists are experts at identifing EAB
• We have Minnesota Department of Agriculture EAB first detectors on staff
• We offer and provide EAB education
• We have treatment options for your valuable trees

Rainbow Answers Your Questions about Emerald Ash Borer (EAB)

1. Is EAB in the Twin Cities?
   EAB was discovered in St. Paul, MN, on May 13th, 2009, by Consulting Arborist Chris Naselli, of Rainbow Treecare.  The MN Dept. of Agriculture confirmed the infestation after reviewing the larvae samples submitted to them.  Further examination of  the affected trees determined that EAB has been present in the Minneapolis, St. Paul area for 3 - 5 years.  At this time we do not know how far the infestation has spread into Minnesota.
2. Why do I need to worry about EAB?
   If you have ash trees on your property EAB will kill them unless you treat it chemically every year. If you don’t have ash on your property you will still experience the devastation of all ash trees along our roadways, in our parks, and in our wooded and forested areas.
3. What does an ash tree with EAB look like?
   The initial stages of the infestation are hard to identify and can last for years before decline is detected. The first noticeable stage of decline is early fall color and leaf drop (pic 1). Trees in the second stage of infestation will exhibit tip die back and a systemic decline (pic 2). As the trees ability to transport water to the leaves is disrupted by borer galleries, die back will move down into the main trunk of the tree (pic 3). In the final stages of infestation, the tree will try to survive by pushing shoots out of the main trunk, this is called epicormic sprouting (pic 4).
   

   picture 1

   picture 2

   picture 3

   picture 4

4. How effective is treatment? If I do annual preventative treatment with XytectTM, what are the odds that my tree will die when the EAB gets here?
   We don’t know for sure. There are only two years worth of data to work with. EAB was discovered in 2002, but the extent of the problem was not known until 2003/04. The initial treatment trial data was not available until 2005. Between 2005 and 2007 researchers started learning what products didn’t work. From 2007 to 2009 we have been discovering what will work, with positive results now being seen. The treatments with Xytect are very promising, but at this point Rainbow Treecare is not yet offering guarantees. With each new years’ worth of research under the belt we will be better able to judge management procedures and make better predictions on the efficacy of management efforts.
5. Is my tree an ash tree?
   Ash trees, all in the Genus Fraxinus, have compound leaves (pic 5), many leaflets on one leaf and slightly grooved light grey bark. The buds and the leaves of the tree are opposite each other on the limb (pic 6). Mountain ash is not a “true” ash tree and is therefore not susceptible to EAB (pic 7).
   

   picture 5

   picture 6

   picture 7

6. Can I wait until my tree gets EAB before I apply a treatment to save it?
   We wouldn’t recommend it. The most effective management of the beetle with insecticide occurs when the xylem tissue that transports water and nutrients is intact and when the concentration of the insecticide is high throughout the tree. Once an infestation gets established in a tree, the xylem tissue is compromised and the uptake and distribution of the insecticide throughout the tree is not as effective.
7. Will this EAB problem ever burn out and be a non-issue?
   No, the beetles have been found infesting woody limbs on re-sprouting trees that are only ¼ - ½ inch in diameter. As long as there are re-sprouts the infestation potential will never decrease.
8. Are there ash trees that I can plant that aren’t susceptible to EAB?
   All native ash trees and their cultivars that are on the market are susceptible to EAB. This includes Green Ash (Fraxinus pennsyvanica), White Ash (Fraxinus americana), Black Ash (Fraxinus nigra) and Blue Ash (Fraxinus quadrangulata). Manchurian ash (Fraxinus mandshurica) appears to have resistance to EAB and has a cultivar available for northern climates produced out of Manitoba (Fraxinus mandshurica ‘Mancana’). However, it has not been widely produced and is therefore difficult to find through most nursery outlets.
   Attempts are being made to cross Manchurian Ash, which has an evolutionary history with the beetle in Asia and thus has developed pest resistance, with native American species. Progress with tree breeding programs is slow, and the hardiness of any cultivars to Minnesota winters will need to be examined prior to recommending them for planting in our region.

Links for additional EAB information:

• www.emeraldashborer.info
• www.mda.state.mn.us/plants/pestmanagement/eab.htm
• www.mda.state.mn.us
• www.dnr.state.mn.us/treecare/forest_health/index.html

 

Please feel free to contact us with any questions and concerns you may have about your trees. We are available to help.