Bronze Birch Borer
Information about the Bronze Birch Borer
The very trees that are so prized by homeowners for their lovely shade and ornamental value are also popular with an unwelcome pest, the bronze birch borer. This beetle can bring about the demise of a birch tree within 2 to 3 years.
Measuring under ½ inch, the adult bronze birch borer is a greenish bronze colored beetle. The female lays eggs after mating in cracks of the birch tree, underneath bark protrusions or in damaged areas of the tree. After only a few days, small whitish larvae hatch and immediately begin eating their way through the bark. Meandering tunnels mark the presence of this pest, often criss-crossing paths as they make their way through the inner bark of the tree. As winter weather advances, the larvae will bore deeply into the sapwood where they will stay through the cold spells.
The bronze birch borer will remain in the larvae stage for a period of one to two years, depending on the weather conditions and the time of year that the eggs are laid. Four instar stages, periods of molting by the larvae as its size enlarges, will be completed before they enter the pupa stage in late spring. The adult bronze birch borer emerges in early June, eating their pathway through the bark, leaving behind a hole shaped as a “D”; a characteristic unique to this species. The life cycle is then repeated.
White birch and yellow birch trees are both types that are highly susceptible to invasion by the bronze birch borer, although the pests are not averse to attacking other varieties of birch as well. Characteristic marks that a tree has been infested by the pest are by the appearance of the uppermost crown of the tree; wilting of top foliage and dying off of these branches indicate their presence. An examination of the tree’s branches and bark will show raised ridges and lumpy areas on the tree, which are proof of the tunneling habits of the beetle. There may also be the “D” shaped holes showing the departure of the adult bronze birch beetle.
As further proof of the presence of the pest, peel away a bit of the bark at the sites of the lumpy protrusions. Underneath will be the irregular paths chewed as the larvae made their way through the destruction. These “galleries” will be increase in size as the larvae advances in the instar stages; growing wider as the larvae does. Often, the bronze birch beetle’s attack begins at the crown of the tree; cutting off the flow of plant sap carrying necessary nutrients.
If a birch tree is one of your favorites, keeping it healthy and in an environment conducive to its growth may very well protect it from invasion by the bronze birch beetle.