Emerald Ash Borer
(Agrilus planipenni)
Biological Category
Terrestrial Invertebrate
NY Legal Status
Prohibited
Species Type
Terrestrial Invertebrate
DESCRIPTION
Bright metallic green wood-boring beetles, body elongated, head flat. The dorsal surface of the abdomen underneath wings is usually a bright red color.
Note: Research for these pages was generated from citations listed. References for specific statements available upon request.
Adults: Bright metallic green wood-boring beetles, about ½ inch long and 1/8 inch wide, body elongated, head flat. The dorsal surface of the abdomen underneath wings is usually a bright red color.
Pupae: 10-15 mm long, creamy white in color. As it develops, it takes on adult colouration.
Larvae: 25–32 mm long at maturity, creamy white in color, brown head, flat, broad shaped body; 10-segmented abdomen, bell-shaped segments, and a fork-like appendage on the tip of the abdomen.
The emerald ash borer is an invasive wood-boring beetle that attacks and kills ash trees. It was first detected near Detroit, Michigan and Windsor, Ontario in 2002, but has likely been in North America since the 1990s. EAB is thought to have been originally introduced to Detroit via infected wooden packaging materials or shipping crates imported from Asia. The beetle has been rapidly spreading across North America since its arrival, posing a serious threat to all species of ash.
Eggs: This life stage is extremely difficult to visually detect during survey. Oviposition sites are likely to be correlated with the direction of sunlight, with the most eggs being laid on the southwestern side of the tree. Recent research indicates that females may prefer to lay eggs in areas where the bark is rough, cracked, or rippled, as may be found near branch crotches. The female may lay 1-23 eggs at a time, with one being the norm. Each female can lay 60-90 eggs in their lifetime, depositing them individually on the bark along the trunk and portions of the major branches. The eggs typically hatch in 7-10 days.
Larva: Minute larvae bore through the bark and into the cambium where they feed on the phloem from late spring to early autumn. There are four stages to larval development. As they feed, the larvae create long serpentine galleries filled with frass, which enlarge in width as they grow. Larvae continue development into fall. Facultative diapause occurs after fourth instar larvae enter the sapwood or outer bark and excavate a pupal chamber where they overwinter as prepupae. Larvae too immature to prepupate spend the winter in the larval gallery and complete development the following spring. Larval galleries are typically 20- 30 cm long.
Pupa: Pupal development is variable according to humidity and temperature. Pupation may begin upon the accumulation of 100-150 growing degree days and, in ideal laboratory conditions, pupal development typically takes approximately 4 weeks. After pupae transform into adults, the beetle takes 1 to 2 weeks before it emerges through D-shaped exit holes 3-4 mm wide. More research is necessary to fully understand pupal development.
Adult: Newly formed adults typically remain in the pupal chamber for 1-2 weeks after pupation is complete. Initial adult emergence predictively occurs when an accumulation of 400-500 growing degree days is achieved. Evidence of adult emergence appears in the form of a D-shaped exit hole 3-4 mm in diameter. Peak activity for adults is predicted to occur at approximately 1,000 growing degree days. Adults are capable of immediate flight and, in laboratory conditions, adults mate shortly after emergence. Females may mate as many as 3 times with mating lasting 20-90 minutes (average of 60 min.). An approximate 3 week period of maturation feeding occurs before oviposition. The adults feed on ash foliage, causing minimal damage. Adults may feign death when frightened or disturbed. They are phototactic and thermotactic and most active on warm, cloudless, windless days. Oviposition begins 7-9 days after the initial mating. Average longevity for adult males is 13 days; average longevity for females is 22 days. EAB adults are strong fliers, with females flying twice as far as males and mated females flying twice as far as unmated females. Tethered flight under laboratory conditions suggests that a mated female may fly more than 20 km.
Ash borers During early stages of infestation, the initial damage is low. However, after two to three years of continuous infestation, there’s a substantial growth in the population, which disrupts the tree’s nutrient and water transport system, resulting in wilting and eventual tree mortality. With favorable hot and dry climates, populations can kill healthy trees quickly. After one to two years of infestation, the bark often falls off, exposing the tunnel-ridden sapwood. They cause D-shaped exit holes along the lower bole surface with frass, filled, zigzagging tunnels are indications of A. planipennis. Within 1/3 to 1/2 of branches die within the first year, exhibiting a top-down die-back, with the rest of the canopy dying the following year.
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