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Deadly beauty By Sharon Moffat

and deadly to ash trees in North America. At present, tens of millions of ash trees have been destroyed in Canada and the United States, and it is expected that the beetle will continue to increase its range. Native to various Asian coun- tries including China, Korea and Japan, the beetle is also found in eastern Russia. In North America, it was first identified in Michigan and in southern Ontario in the city of Windsor in 2002; though it had likely already been here for several years. As of 2014, it has invaded various locations in southern Ontario,

T includ-

ing Toronto, and into Quebec, including Montreal. In the US, it has been expanded to almost all of the eastern states, as far south as Louisiana, Colorado in the west and St. Paul, Minnesota in the north. The emerald ash borer

(Agrilus planipennis) belongs to the family of insects called metallic wood-boring beetles or jewel beetles, which is clearly seen in the shiny, vivid, deep-green colour of the adult. The size of the adult beetle ranges from 7.5 to 15 mm in length and about 3 to 3.4 mm in width. The larvae are much longer and grow to about 30 mm in length as they develop through four growth stages. The entire life cycle usually takes one year to complete but in colder climates, like those found in most of Canada, the life cycle can take up to two years to complete. It is the larval stage that is destruc-

tive to all species of ash trees. While adult emerald ash borers (EAB) will feed along the edges of the leaves, the larvae feed under the ash trees’ bark, in the tissues that transport nutrients throughout the tree. Eventually this feeding effectively girdles and kills the tree by blocking the channels that trans-

32 • Spring 2015 The Emerald Ash Borer, adult stage (above) and pupae (below).

he Emerald Ash Borer is a beautiful looking insect, but

is invasive

shoots in response to the damage done by these beetles. Epicormic shoots develop lower down on the tree trunk, below the area of insect damage. Signs of EAB infestations can

also include trunk

and bark deformities, the presence of increased numbers of woodpeckers and squirrels, and distinc- tive D-shaped holes in the bark that are about 3.5 to 4 mm wide; the exit holes of new adults emerging from the tree. While all of these symptoms can occur in ash trees for various reasons, the symptoms in EAB infested trees usually occurs more quickly than under

other stressors,

often in the first year or two of infestation. One of the main meth-

ods to control the spread of the emerald ash borer is to be vigilant in not trans- porting ash firewood or other ash products such as bark chips. Keep trees healthy with proper and adequate watering, ferti- lizing and pruning of dead and damaged areas. If an ash tree is suspected to be affected by EAB, the area municipality should be contacted as once EAB is established in a tree, it is usually in many more nearby ash trees and exten- sive monitoring will need to be conducted in hopes of eradicating the emerald

port water and nutrients to the crown. Short of actually finding the adult

beetles on a tree, the first indication that a tree may be under attack by emer- ald ash borers is noticing symptoms of decline in an ash tree. Main symptoms of an EAB infestation include flagging or yellowing of leaves in the crown of the tree, crown thinning, branch dieback and entire

dead branches. Infested trees often put out epicormic

ash borer from the area. While there are insecticidal options, to date they are primarily only commercially available for highly prized trees, though with continuing emerald ash borer research more options may become available in the future. q

Sharon Moffat has a Plant Science degree from the University of Manitoba and has worked for the City of Winnipeg's Insect Control Branch for the last 24 years.

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