Parks Tree

"Climbing to New Heights"

Emerald Ash Borer

(Agrilus planipennis Fairmaire),
an invasive insect native to Asia, has killed tens of
millions of ash trees in urban, rural and forested
settings. This beetle was first discovered in 2002 in
southeast Michigan and Windsor, Ontario. As of June
2009, emerald ash borer (EAB) infestations were
known to be present in 12 states and two Canadian
provinces. Many homeowners, arborists and tree
care professionals want to protect valuable ash trees
from EAB. Scientists have learned much about this
insect and methods to protect ash trees since 2002.
This bulletin is designed to answer frequently asked
questions and provide the most current information
on insecticide options for controlling EAB


I know my tree is already infested with EAB. Will insecticides still be effective?


If a tree has lost more than 50 percent of its canopy, it is probably
too late to save the tree. Studies have shown that it is best to begin
using insecticides while ash trees are still relatively healthy. This is
 because most of the insecticides used for EAB control act systemically —
 the insecticide must be transported within the tree. In other words, a
tree must be healthy enough to carry a systemic insecticide up the trunk
 and into the branches and canopy. When EAB larvae feed, their galleries
 injure the phloem and xylem that make up the plant’s circulatory
system. This interferes with the ability of the tree to transport
nutrients and water, as well as insecticides. As a tree becomes more and
 more infested, the injury becomes more severe. Large branches or even
the trunk can be girdled by the larval galleries. Studies have also
shown that if the canopy of a tree is already declining when insecticide
 treatments are initiated, the condition of the tree may continue to
deteriorate during the first year of treatment. In many
cases, the tree canopy will begin to improve in the second year of
treatment. This lag in the reversal of canopy decline probably reflects
the time needed for the tree to repair its vascular system after the EAB
 infestation has been reduced.