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Trees and their enemiesColorado Every type of tree variety has a specific insect vector that is attracted to it when a tree becomes stressed. There are times when borers enter trees because of an open wound or exposed decaying cambium from improper pruning or breakage during a storm. The cambium is a thin layer of cells which are constantly dividing and forming new wood which in turn increases the girth of the tree. Sometimes a particular insect vector can attack more than one type of tree variety. Cottonwoods, ash, elm and other hardwoods can attract the carpenterworm. These larvae tunnel into the sapwood which continues further inside the tree behind the active cambium layer. These carpenterworms go deeper into the tree's center called the heartwood. Trees heavily infested may break large limbs during high wind storms. Trees may also appear gnarled and misshapen when the vector has chronically infested these trees. This is common in "shelterbelts" or windbreaks in Eastern Colorado. The one most distinguishing characteristic from other borers is an exterior opening in the bark of the tree by which it expels sawdust. The larvae can reach 3 inches in maturity. The adults are moths which appear as adults in May. The moths have stout bodies with grayish-mottled forewings. This is one of the many different types of borers. Borers can be beetles and moths. But the important thing to keep in mind is that they do the most damage in their larval stage. Just like children, they need food to grow. They can eat a lot in one season for some, but with others like the cottonwood borer, a beetle, takes two seasons to complete their lifecycle. Cottonwood borers, beetles of an inch and a half long with yellow and black markings feed in the bark and down into the larger roots the first fall. The second season they tunnel into the galleries of the tree base. Trees like willows, cottonwoods and poplars tend to attract this insect. Mostly, this insect occurs in southeastern Colorado. Pole borers are a reddish-brown beetle about three-quarters of an inch long which enters where the cambium is exposed to the environment. After several attacks the insect is associated with a wood fungus. The key is they come to damaged or wounded sites on the tree which attains high moisture content. Again, trees can break off limbs in high wind storms. These insects get their name from the telephone poles or other poles having their bases covered with soil. These pole borers take up to three years to complete their lifecycle. What does one look for when inspecting their trees in spring? First see if there are any exit holes and fresh sawdust. Second, look for sap or pitch either in the crotches of branches or on the bark of the trunk. Third, look for swellings on larger branches and sometimes even on the trunk. Fourth, look for bark at the base of the tree that peels off easily. If there are tunnels immediately behind the bark, the tree may have borers. Identification is necessary with the adult stage of the insect. The larval stage is the most difficult to distinguish between these insects. If you would like more detailed information on the different types of borers for Eastern Colorado, go on-line to Colorado State University Extension website. There is a fact sheet titled Shade Tree Borers and number 5.530. Since there are so many different types, it makes it too numerous to place in one article. There are colored pictures on the fact sheet which will be of help, if you happen to see a problem and spot an insect of this type. Treatments vary according to the family in which the insect is classified. There are some borers in the butterfly family and some in the beetle family. Certain chemicals are more effective with the beetle family. First and foremost, the identification of the insect must be made before determining a solution to the problem. Keeping trees properly watered will help a tree with its own immune system. Water carries nutrients throughout the vessels of the tree. Water helps the tree produce proteins and enzymes. Without water, the tree stops actively growing. This is similar to humans. Without water for humans, our body stops functioning. Without the proper amount of water a tree can survive, but it may not be surviving in a healthy way. Borers are most effectively taken care of by prevention. It is difficult to know if borers are present unless you see some sort of pitch on the bark or an exit hole in the tree. And by that time, a significant amount of damage can be done. Borers are the trees' cancer. They are silent, but deadly and until the damage has advanced no one but the tree knows they are present. If you have any questions or concerns, please call your local Extension office. 3/24/08 Advertisement
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