AMES, Iowa – Knowing how to properly care for trees and how to identify harmful tree abnormalities is a great skill for all tree owners to have. However, not all tree abnormalities are harmful.
AMES, Iowa – Knowing how to properly care for trees and how to identify harmful tree abnormalities is a great skill for all tree owners to have. However, not all tree abnormalities are harmful. Horticulturists with Iowa State University Extension and Outreach identify some tree abnormalities and explain what exactly they are.To have additional questions answered, contact the ISU Hortline at email@example.com or call 515-294-3108.
The wartlike growths on the hackberry leaves are called galls. Galls are abnormal growths of plant tissue induced to form by mites, insects or other small organisms. They are quite common on trees.
The gall found on the hackberry leaves is referred to as the hackberry nipple gall. The hackberry nipple gall is so common on hackberries that its presence can be used to identify the tree.
While galls may be unsightly, they do not cause serious harm to healthy trees. Preventive insecticide treatments are seldom warranted.
The white, fuzzy objects on the branches of your maple tree are called wooly alder aphids. The insect also is known as the maple blight aphid. Wooly alder aphids feed on the sap of maple trees from bud-break until late June.
Winged adult wooly alder aphids, some with abdomens covered in white fluffy wax, are produced in colonies. These winged migrants readily fly when disturbed and create the illusion of tiny masses of cotton floating through the air. The winged adults leave the maple tree and fly to alders where they establish new colonies on the secondary host. Wooly alder aphids require both maple and alder trees to complete their life cycle.
While the presence of white, fuzzy colonies of wooly alder aphids on a maple tree may cause alarm, they don’t cause serious harm to infested maples. Damage is usually limited to the loss of some leaves. Large wooly alder aphid populations usually collapse from predation and parasitism. Control efforts are not necessary.
The gray-green patches are probably lichens. Lichens are unusual organisms. They consist of two unrelated organisms, an alga and a fungus. These two components exist together and behave as a single organism. The alga provides food via photosynthesis while the fungus obtains water and minerals for itself and the alga.
Lichens are common on trees because the bark provides a suitable place to gather sunlight and to grow. They grow especially well on dead branches because they receive more sunlight. In addition to growing on the trunks and branches of trees, lichens can be found on: exposed soil surfaces, rocks, wooden fence posts, shingles, gravestones, stone walls and other sunny surfaces. Lichens may be flat, leafy or branched and hairlike. Lichens on trees are often gray-green. Other species may be: orange, yellow, slate blue or black.
Lichens are fascinating, unique organisms. However, they do not harm trees.
PHOTO: Galls also are common on maple trees. Galls that are formed by insects or mites are basically out growths of the plants tissue.