e03. How do pathogens and insects affect trees?
Parasitic fungi cause the most destructive tree diseases. Chestnut blight
from China, Dutch Elm disease from Asia via Europe, and white pine blister rust
from Europe affect US forests. Insects directly attack parts of the tree. For
instance, bark beetles bore channels through the bark, eventually loosening it.
The pine bark beetle devastated Yellowstone lodge pole pines. Spruce bud worm
and gypsy moth larvae eat the leaves or needles of the tree, interfering with
photosynthesis. Biodiversity is the cheapest and best defense against disease.
Fires help control diseases and pests. Surface fires usually only burn undergrowth and leaf litter. Crown fires are very hot; they burn whole trees and leap from tree-top to tree-top. Prescribed burning can reduce the risk of crown fires by reducing the litter build-up. Ground fires are mostly found in the northern peat bogs; they may smolder beneath the peat for days or weeks.
m02. Are there other threats to forests?
m03. How can the forests, as resources, be sustained?
m04. How are National Forests managed?
m05. How does recycling paper affect forests?
m16. How are forests of commercial importance?
m17. What’s happening to the tropical forests?
m19. What can be done to reduce the destruction of tropical forests?
m44. Why are there detractors of pesticides?