People can unknowingly
kill their own trees
By Gregory Koteles
Staff Writer

In Southern California’s desert climes, there are few natural resources more treasured than trees. They offer shade from the famous California sun and add a touch of beauty to an otherwise stark landscape.

Though few things appear as strong and resilient as trees, danger abounds for them as for any living organism. There are more threats to trees than just drought–including disease, infestation and human beings.

Infestations pose a significant threat to local trees. The Woolly Aphid and the Australian import, Lerp Psyllid, an insect which attacks the leaves of red gum eucalyptus trees, have cropped up in the last couple of years, according to Kay Greeley, landscape engineer for Agoura Hills and city arborist for Calabasas.

"We’re losing a lot of trees in California to the Lerp," said Greeley. Though aggressive tactics such as bringing in a predatory wasp from Australia that lays its eggs in Lerp larvae have been employed to fight the pest, they’ve failed to eradicate the infestation.

Disease also poses a risk to trees, said Greeley, but the local area experiences few. Some trees on Parkway Calabasas suffer from fire blight, a bacterial disease that attacks mostly pear trees. It causes branches to get mushy and appear as if they’re burnt.

However, according to Greeley, the greatest danger––by far––to trees is "bad trimming."

The practices of "topping" and "stubbing" are twin evils, according to Greeley.

Lobbing off the tops and sides of trees by untrained and unqualified people––attempting to make trees conform with unrealistic perceptions of ideal size and proportion––create trouble for trees.

"If you get a paper cut, within a month you can’t tell you ever had it. The cells are replaced," said Greeley. "Tree cells grow around the wound in a process called compartmentalization."

Improperly pruned trees can suffer from an imbalance that causes weakened branches, posing a falling threat, and other stresses that ultimately result in "disfigurement, disease or death."

Greeley recommends that people wishing to trim their trees call an arborist certified by the International Society of Arboricul-ture, which has established standards for pruning.