Emerald ash borer
|Emerald ash borer|
The emerald ash borer, Agrilus planipennis, is a green beetle native to Asia and Eastern Russia. Outside its native region, the emerald ash borer (also referred to as EAB) is an invasive species, and emerald ash borer infestation is highly destructive to ash trees in its introduced range. The Emerald Ash Borer was first discovered in America in June of 2002 in Michigan. It is believed to have been brought to America unintentionally in ash wood which was used to stabilize crates during shipping.
A. planipennis may take one or two years to complete its life-cycle depending on 1) the timing of egg deposition, 2) the health and stress level of the tree, and 3) local temperatures. The one-year EAB life-cycle is described below.
Adults The adult beetle is dark metallic green, bullet-shaped and about 8.5 millimetres (0.33 in) long and 1.6 mm (1⁄16 in) wide. The body is narrow and elongated, and the head is flat with black eyes. Adults begin to emerge from the trunks of ash trees after the accumulation of 400-500 growing degree days base 50°F (GDD). Peak adult emergence occurs at ~1000 GDD. After emergence, adults fly into the ash canopy where they feed on leaves throughout their lives. EAB adults start mating one week after emergence, and females begin laying eggs 2–3 weeks later. In the field, EAB adults are readily observed mating and egg-laying on the trunks of ash trees on warm, sunny afternoons and evenings. The adults of both sexes are strong fliers.
Eggs A female EAB may lay >100 eggs in her lifetime, depositing them individually or in groups on the bark along the trunk and portions of the major branches. Eggs are laid in areas where the bark is rough, and between bark layers or in bark crevices. Eggs are approximately 1.0 mm long x 0.6 mm wide and creamy white when laid; fertile eggs gradually turn amber after a few days. The eggs hatch after about two weeks.
Larvae Newly hatched larvae bore through the bark to the phloem and outer layer of new sapwood where they feed until the weather gets too cold in the fall. There are four stages of larval development (instars). As they feed, the larvae create long serpentine galleries filled with frass, which enlarge in width as they grow. Larvae are creamy white, and dorso-ventrally flattened. When fully mature, fourth-instar larvae are 26 to 32 mm long. Their head is mostly retracted into the prothorax with only the dark brown mouthparts visible. The prothorax is enlarged, with the mesothorax and metathorax more narrow. Larvae have 10 bell-shaped abdominal segments and a pair of small brown structures called urogomphi, which are characteristic of all larvae in the genus Agrilus.
Overwintering larvae, pre-pupae, pupae, and adults In the fall, mature fourth-instar EAB larvae excavate pupal chambers in the sapwood or outer bark where they fold into overwintering “J-shaped larvae”. In the spring, the J-shaped larvae shorten into prepupae then shed their cuticle to become naked pupae. Pupae are initially creamy white, but the eyes turn red and the body begins to darken as they develop. To emerge from ash trees, adults chew D-shaped exit holes through the bark and are capable of immediate flight upon emergence. EAB larvae that are immature as cold weather arrives in the fall will simply overwinter in their larval gallery. Larger larvae complete development the following spring, whereas smaller larvae may require another summer of feeding to complete development.
Effect on trees
The most significant damage to a tree by the emerald ash borer takes place when the insect is in its larval stage. In an infestation, bore holes and serpentine feeding galleries of the larvae essentially disrupt the flow of nutrients as they rise up the trunk from the roots to the crown via the phloem (the tree's vascular structures) just under the bark. This eventually results in the death of the tree. This can take place over a number of years, and the first noticeable sign is usually some die back in the crown of the tree. The tree will usually be dead by the following year or soon after. In areas where the insect is invasive and has no natural predators, it can and usually does have a devastating effect on the local ash tree population.
Prevention of EAB is possible by the use of a systemic insecticide into the base of the tree. This treatment can prevent damage to the tree for up to two years. Note that application must be reapplied every two years. Soil injections are another option for the prevention of EAB. These insecticides are injected directly into the soil surrounding the base of the tree, and are then transported through the rest of the tree via the roots. In order for these treatments to have the greatest effect soil must be moist when applied. Water logged or dry soils will result in less of the insecticide to be absorbed into the tree. There are two insecticide spray treatments that can be used as well. The first is a spray which is applied to the trunk and absorbed through the bark. This treatment is less invasive to the tree and soil, however if the tree has thick bark absorption is slow and limited. The second spray treatment is a protective cover spray, which is applied to the branches and trunk of the tree. This treatment kills adult beetle and newly hatched larva; however it will not kill eggs.
It is estimated that there are 8 billion ash trees in the United States. Since the arrival of the Emerald Ash Borer, approximately 150-200 million ash trees have already died and this number is expected to rise. The EAB travels by the movement of firewood and nursery stock. The beetle once in its adult life stage can also fly up to a half mile under their own power. The Emerald Ash Borer has spread to 22 states within the United States as well as Canada, since its discovery in 2002. The following link will take you to a map illustrating the spread of EAB. http://www.emeraldashborer.info/files/MultiState_EABpos.pdf States are attempting to decrease the spread of EAB by placing quarantines on infected areas and not allowing the transport of ash nursery stock or logs or fire wood.
- "Data sheets on quarantine pests: Agrilus planipennis". OEPP/EPPO Bulletin (European and Mediterranean Plant Protection Organization) 35 (3): 436–438. 2005. Retrieved August 28, 2013.
- "Agrilus planipennis (insect)". Global Invasive Species Database. ISSG-IUCN. August 14, 2006. Retrieved August 28, 2013.
- "Emerald Ash Borer". Don't Move Firewood. Retrieved August 28, 2013.
- Gould, Juli S.; Bauer, Leah S.; Lelito, Jonathan; Duan, Jian (May, 2013), Emerald Ash Borer Biological Control Release and Recovery Guidelines, Riverdale, Maryland, USA: USDA-APHIS-ARS-FS, retrieved August 28, 2013
- Emerald Ash Borer - The Morton Arboretum
Herms, D. A., McCullough, D. G., Smitley, D. R., Sadof, C. S., & Nixon, P. L. (2009, June). Emerald Ash Borer. Retrieved September 27, 2013, from http://www.emeraldashborer.info/files/Multistate_EAB_Insecticide_Fact_Sheet.pdf
Kovacs, K. F., Haight, R. G., McCullough, D. G., Mercader, R. J., Siegert, N. W., & Liebhold, A. M. (2010). Cost of potential emerald ash borer damage in U.S. communities, 2009?2019. Ecological Economics, 69(3), 569-578. Retrieved from http://www.sciencedirect.com/science/article/pii/S0921800909003681#
McCullough, D., & Usborne, R. (2013, September). Frequently Asked Questions | Emerald Ash Borer Information Network. Retrieved September 27, 2013, from http://www.emeraldashborer.info/faq.cfm#sthash.eVXX903U.dpbs
Partain, C. (2012). Ashes to Ashes. Natural History, 120(8), 48.
USDA (2013, September 5). Cooperative Emerald Ash Borer Project [Map]. Retrieved from http://www.emeraldashborer.info/files/MultiState_EABpos.pdf
|Wikimedia Commons has media related to Emerald ash borer.|
|Wikispecies has information related to: Agrilus planipennis|
- New interview about EAB with prominent Research Entomologist
- United States Department of Agriculture Public Awareness Campaign
- Emerald Ash Borer Most Frequently Asked Questions - A site dedicated to answering the most frequently asked Emerald Ash Borer/Treatment Questions
- Canadian Food Inspection Agency
- Multinational EAB website - US states and Canadian provinces
- "Emerald ash borer". United States Department of Agriculture.
- Southeast Michigan Resource Conservation & Development Council - Ash Utilization Options Project - developing value-added products from ash trees affected by the emerald ash borer
- Emerald ash borer Indiana Information
- Ontario Ministry of Natural Resources
- Ohio Department of Natural Resources page on EAB
- USDA Forest Service Northern Research Station link to research on EAB
- Ohio Department of Agriculture infestation PDF map
- Wisconsin's Emerald Ash Borer Information Source
- Minnesota releases Stingless wasps to fight against emerald ash borer
- Species Profile- Emerald Ash Borer (Agrilus planipennis), National Invasive Species Information Center, United States National Agricultural Library. Lists general information and resources for Emerald Ash Borer.
- The short film Emerald Ash Borer: The Green Menace is available for free download at the Internet Archive [more]