Flat Headed Borers

Tree boring insects can cause massive amounts of physical damage to the trees most important system, the vascular system.

These insects feed on the phloem just under the bark of the tree. Damage to the phloem blocks the movement of sugar and water between the leaves and roots. Trees naturally defend against borers by hardening off cells around the insect and not allowing it to continue to move and feed within the vascular tissue. When there is a high population of insects or environmental factors such as a drought comes into play, the trees natural defense is weakened and unable to fight off the insects. This will lead to the decline of the tree and can ultimately lead to its death.

Symptoms:
Often times you will not notice that a tree is infested with borers until the tree starts to show signs of decline which means that its natural defenses are not working.

Bronze Birch Borer:
Yellowing or dying leaves near the top of the canopy followed by the death of a few branches. Horizontally raised scar tissue under the bark of the trunk and branches.
Affects: All birch trees, especially paper, white and gray

Two-Lined Chestnut Borer:
Overall decline of the tree, small “D” shaped exit holes can be found on the trunk or branches.
Affects: Oaks and Chestnuts

Emerald Ash Borer:
Has made its way to Minnesota. The adult beetles nibble on ash foliage but cause little damage. The larvae (the immature stage) feed on the inner bark of ash trees, disrupting the tree’s ability to transport water and nutrients.
Affects: All Ash species

Management
The solution to this problem is through the use of systemic insecticides and frequent watering.The systemic insecticides are taken into the vascular system of the tree and kill the borers living and feeding there. The treatment should be applied preventively for highly susceptible trees, especially during dry summers, but can also be used to stop further destruction of the tree after an infestation of borers is found.

In Season Treatment: Apply a fast uptake, short residual systemic insecticide immediately.

Preventative Treatment: Apply a slow uptake, long lasting systemic insecticide in fall to protect the tree for entire next growing season.

Download PDF

Useful links:

U of M: Bronze Birch Borer Forest Service: Two Lined Chestnut Borer MN Dept. of Ag: Interactive Map U of M: EAB in Minneapolis

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