Green Balls That Grow on Oak Trees
Oak trees are prone to infestation from a variety of pests, many of whom are identified by the damage that they inflict on the tree. These pests include a number of tiny wasps that create small balls, referred to as galls, on oak trees. The exact identification of the wasp is usually established by the size and color of the gall. Certain wasp species cause the growth of green galls on oaks.
Pest Identification
The oak apple gall and the roly poly gall are among the green galls seen on oaks. The pests are common on all varieties of oaks in all oak growing regions. Though a number of other pests such as fungi, bacteria or mites may also cause the growth of galls on trees, wasps are the most frequently cause of this disorder, cites the University of Lincoln-Nebraska Extension.
- Oak trees are prone to infestation from a variety of pests, many of whom are identified by the damage that they inflict on the tree.
- Though a number of other pests such as fungi, bacteria or mites may also cause the growth of galls on trees, wasps are the most frequently cause of this disorder, cites the University of Lincoln-Nebraska Extension.
Pest Description
There are about 1,400 different types of gall-creating wasps of which 80 percent infest only oak trees. The wasps are very small in size, measuring ΒΌ inch or less in length. The insects come in shades of red, yellow or black depending on species. The legless larvae and pupae are white. Every gall wasp is identified by the distinct characteristics of the resulting galls.
Gall Production
Galls are small, round balls that may be up to 2 inches in diameter or may be too small even to be noticed. The galls are actually abnormal plant growth resulting from wasp feeding that creates a disturbance in the normal growth process of plant tissues. As a reaction to pest feeding, the plant produces excessive amounts of growth regulating chemicals that in turn disrupts the normal cell growth. The galls contain the eggs and larvae of the wasp. The emerging larvae feed only the gall's tissues and not on tree areas.
- There are about 1,400 different types of gall-creating wasps of which 80 percent infest only oak trees.
- The galls are actually abnormal plant growth resulting from wasp feeding that creates a disturbance in the normal growth process of plant tissues.
Control Strategies
Galls are primarily a cosmetic disorder of the affected tree and pose little threat to tree health. Foliage galls sometimes cause premature leaf drop or distortion by affecting the normal process of photosynthesis. There are no control options to reduce or eliminate galls once they have occurred. Using preventative insecticides may control populations of the adult wasps before they have a chance to lay eggs. Unless preventative pesticides are targeted precisely at wasp flight time, however, they will be of little use. Keep tree areas clear of debris and fallen foliage to remove overwintering pests in branches, twigs and leaves.
Related Articles
References
Writer Bio
Irum Sarfaraz is a freelance writer with over 20 years of nonfiction writing experience in newspaper op-eds and magazine writing, book editing, translating and research writing. Sarfaraz is originally from Pakistan and has been published in both American and Pakistani newspapers and magazines. She holds a Bachelor of Arts in English literature, and diplomas in nonfiction writing.
