Galls - What Are They?

GALLS - Deformations or overgrowths of plant tissues caused by the irritation produced by bacteria, fungi or insects. Bacteria cause the tumors on the stems and crowns of such plants as blackberries and roses. The cedar-apple is a single cedar leaf deformed by a rust fungus. Such galls as the cockscomb gall of elm and the hard spruce gall are due to aphids. A group of plant lice called Phylloxera cause the leaf galls abundant on some trees and on grapes. A large group of insects called gall wasps cause various types of deformations, particularly on oaks, among them the familiar oak-apple.

The life history of some of these gall makers has what is known as alternation of generations, the second generation producing a gall very different from the first, but the third resembling the grandparents. The gall midges (Itonidae) most frequently attack herbaceous plants such as chrysanthemum; to prevent these conical leaf galls, the grower must watch for and destroy the mature insects when they emerge, which is always between midnight and 4 a. m.

Related Articles

• Daddy Long Legs - DADDY-LONG-LEGS. A common or child’s name for insects belonging to the spider group and also called harvestmen. They resemble round-bodied, very long-legged spiders, the legs being carried with the “knees” high. It is not known whether this creature feeds on injurious insects enough to be called beneficial, but it does not bite, sting or injure
• Earwigs - EARWIGS - Chewing insects of the order Dermaptera, meaning skin wing, resembling beetles in their hard wing covers but distinguished from them by pincher-like appendages at the tail end. The hind wings are folded both lengthwise and crosswise. Earwigs are troublesome plant pests in the South and on the Pacific Coast, feeding on the petals