Current Tre and Shrub Issues (Summer 2006)

Aphids and Drought?

This has been a banner summer for aphids. Heavy feeding has resulted in either deformed, puckered leaves; or, has resulted in yellowing leaves falling prematurely from the tree. Aphids usually occur with other stress factors affecting the tree such as drought, or other pests, or diseases.

Small trees, confiferous evergreens and all newly planted trees and shrubs should be thoroughly watered weekly during dry periods. Add one inch of water a week to the entire feeding root area. This feeding area in principle is the area swept out by a radious from the trunk equal to half the height of the tree.

Other common problems that have developed this year or have gotten worse this year are the following:

Hawthorn - Juniper Gall Rust disease in Rocky Mountain Juniper
Photo: © M. Allen

Box elder twig borer expanded feeding area in twig of Manitoba maple
Photo: © M. Allen

Rust diseases in the fruits of crab apples, hawthorns, cotoneasters, currants and gooseberries. Plants are alternate hosts to complex fungi whose life cycles grow and develop on two different species of trees or shrubs. One stage of the rust disease on hawthorns, for example, grows on Rocky Mountain junipers such as Medora nad Wichita Blue.
Manitoba maples (or Box Elders) have been infested with heavy aphids causing yellowing and dropping of leaves. This situatin is made worse by teh prsence of the Box Elder Twig Borer feeding inside twigs and small branches. Look for swollen twigs and twigs with an 'exploded' hole in them. This destructive insect is a round headed wood borer and it usually attacks stressed maples. I have also seen the same insect feeding inside the twigs of North West poplars this summer.
Spider mites have been devastating on many columnar cedars throughout souther Manitoba. The leaves go grayish and very fine webbing can often be seen in those gray leaves. left uncontrolled, the leaves will die in large numbers.