Question
leaves
Fruitless olives have multiple orange fuzz balls on the underside of the leaves. Two applications of organicide barely reduced the numbers. Are these killing my trees or harmless?
AnswerIt looks like a leaf gall. Galls are abnormal growths on leaves, twigs and flowers, appearing as warts, bumps, or balls and are caused by insects and mites. Mechanical damage or salivary secretions from the pest initiate production of plant growth hormones that stimulate the growth of the gall. The shape, size, and color are extremely variable, but appearance of the galls is unique to the insect causing them. Most gall-making insects and mites are not harmful to the host plant. Control attempts are rarely justified and usually are unsuccessful because the gall protects the insect within it. Some of the galls are quite interesting, adding a touch of uniqueness to plants.
Once the gall appears on the leaf, there is no way to control it. Preventing most leaf galls is extremely difficult. However, other than being unsightly, most leaf galls are not harming the tree or shrub. I would not worry about them the galls do not effect the health of the tree.
