Estimation of the Effects of Phytophagous Insects on Forest Production

Abstract

Insects may damage woody plants in a variety of different ways and, consequently, their potential to reduce the photosynthetic capacity or net primary production of forests is considerable:

• 1. Foliage consumption deteriorates the physiological condition of the tree, decreases the photosynthetic biomass, and indirectly affects the wood increment and the formation of reproductive organs.

• 2. Sap consumption also deteriorates the physiological condition of the tree and reduces foliage and wood production, but not to the extent as does the consumption of photosynthetic tissues by phytophages.

• 3. Consumption of woody tissues decreases wood production; it also can disrupt sap flow and, therefore, deteriorates the overall condition of the tree. However, wood consumption generally affects weakened plants or their parts, and damage to the entire forest stand caused by xylophages is not as great as with foliage consumers. In fact, dead wood consumption may be beneficial to plants, since it thins the nonproductive, but light-intercepting parts of trees.

• 4. Insect damage to reproductive organs (at all stages of their development) may decrease fruit production and reduce the reproductive potential, but normally it does not influence the foliage and wood increment of growing trees.