This tongue twister
of a pest with a passion for Fraxinus flowers has a curious life cycle.
A small mite, Eriophyes fraxiniflora can cause
unsightly damage to your Ash trees.
To be clear this pest only attacks the Male flowers of the
ash tree. Ash are a dioecious species, that being trees that have only male
flowers on one set of individuals of the species and female flowers on the
other set of individuals. Female ash trees bear copious numbers of winged seeds
that can be a nuisance in the landscape. For this reason many people plant only
male trees and this makes an abundance of available hosts for this pest.
The damage from
this pest, twisted brown galls are most visible in the dead of winter, but the
injury occurred months earlier when the trees flower in spring. The normal progression is for the flowers to
fall off the tree once they have completed flowering. However as the summer
progresses the distorted mite damaged flowers remain on the tree and turn into
unsightly brown balls. While the trees will not be killed by this activity
their twig growth will be very distorted.
The mites become
active as new tissue emerges in the spring and they begin to dine on unfolding
tissue. They secrete tissue distorting chemicals as they feed and the ash tree
forms galls.
Control of these
pests can be difficult but early season horticultural oil will provide some
control if applied when buds first break. Similarly miticides applied at this
time will control these pests. Ash trees flower early in spring and care must
be taken to time the applications correctly.
Ash trees are
currently under pressure from the potential of Emerald Ash Borer infestation
and are not recommended for planting. Keeping them healthy and growing strong
can help protect them from other insect infestation.
If you have
questions, Certified Arborists are industry recognized experts in plant insect
and diseases control. Contact your I.S.A. Certified Arborist to see if you have
this damaging plant pest.
