|
A beautiful green tree may already be infested, or worse, dead. The tree can remain green for 12 months or longer after a fatal beetle attack. By the summer and fall of the year following an attack, the tree will start to turn yellow then red because the green chlorophyll in the needles is gone. Beetles will have reproduced and the young left the tree by the time it is red or gray. The red tree will finally change to gray when the needles begin to shed. This process can take up to 3-4 years. It is best to assess your trees in the summer immediately after the flight.
Generally it is thought that 40 successful attacks per square yard will be fatal to the tree. The difficulty is how to access whether the attacks have been successful or not. Sometimes blind attacks occur and these are almost impossible to find if the timing of observation isn’t perfect. It is important to note that when the first few beetles successfully attack a tree, they will emit a pheromone that will attract more beetles into the area. Also, for every beetle that mates inside your tree, up to 60 will emerge next year. Even lightly attacked trees may succumb to further beetle attack in the following year as these trees are highly attractive to beetles. This makes prevention the most important part of any beetle management strategy. Just like interest compounding on a bank loan, early prevention and suppression efforts are the methods mostly likely to succeed in the long run by keeping beetle numbers from growing exponentially.
Look for:
Pitch Tubes:
The first signs of attack are small holes. Whitish globs that look like dried, crusty honey scattered over the bole of the tree are called pitch tubes and are caused by trees producing resin to “pitch out” beetles as they bore into the bark. Large pitch tubes often indicate unsuccessful attacks while very small pitch tubes or no pitch tubes at all may indicate successful attacks.
Boring Dust:
Small mounds of ‘sawdust’ at the base of the tree and in the bark crevice. Boring dust is left when the beetles bore into the bark of the tree. This will have the consistency of flour or fine sawdust and will be reddish in color.
Bark:
Remove a section of the bark to reveal any tunnels created by the beetles. Tunnels indicate a successful attack. At times these tunnels will also contain grubs. Use this method carefully as this will injure the tree and leave it more susceptible.
Woodpeckers:
Woodpeckers find the larvae particularly delectable so an abundance of these birds can also be a good indication of tree infestation.
Blue Stain:
Beetles bring with them a fungus called ‘Blue Stain’. A tree with blue stain fungus is a clear sign of beetle attack; but unfortunately this fungus is only visible when the tree is cut.
NOTE: Beetles prefer to bore into a tree where the bark is the thinnest, namely in the cracks and crevasses. This can make it very difficult to determine the number of beetle hits, and whether or not the hits were successful .
|
