1. Forest insects and pathogens: ecology and managementby
Kristen Baker

2. Insect Feeding categories
Foliage: defoliators, reduce capacity for photosynthesis.
Stems: bark beetles may kill whole tree or individual branches
Cone and seed feeders
Twig and shoot insects: damage new buds and growth
Root insects

3. Biotic causes of plant disease
Fungi - most common
Nematodes
Bacteria
Viruses
Protozoa
Parasitic plants

5. The Disease Triangle
Amount of Disease
Pathogen
Environment
Host

6. Management and control options
Chemical
DDT, copper sulfates, botanicals
Biological
use of one organism to control adverse effects of another (natural enemies such as insect predators, viruses, pathogens)
Cultural
active management of vegetation to prevent or reduce damage or decrease pest population

7. Integrated pest management
Use of a combination of control techniques that are ecologically, economically, and socially acceptable
Does not mean eradication necessarily, but reduction of pest to tolerable level

8. Native insects and pathogens
Regulators of forest ecosystems
cause mortality of weakest trees
create gaps within forest, increase nutrient cycling, available light, insects may increase nutrient availability
provide wildlife habitat (snags and downed woody debris)

9. Example: bark beetles
Many species, some cause widespread mortality of trees, others create small pockets of dead trees
Kill trees by mass attacking: many beetles attack the same tree and breed within the tree

10. Example: root diseases
Fungi that cause tree decline and death by attacking root system (disrupts water uptake by tree)
Often creates distinctive circular patches of mortality
Creates conditions for non-susceptible species to establish in forest

11. Exotic insects and pathogens
Non-native to an area: abnormally large amounts of mortality common
Insects: natural enemies not present in new location to control population
Pathogens: no co-evolution for genetic resistance to pathogen; long life span of trees a problem

12. Example: balsam woolly adelgid
Native to central Europe; introduced to North America ~1900
Adelges piceae
Infests true fir (balsam fir, Frasier fir, subalpine fir, grand fir)
Feeding causes host to produce “early heartwood”, reducing water transport.

13. Management and control
Biological control
insect predators, pathogens
limited success to date
Environment
cold winter temperatures
early or late frost

14. Example: white pine blister rust
Introduced from Europe ~1900
Infects all 5-needled pines: sugar pine, eastern and western white pine, whitebark pine

15. White pine blister rust

16. Whitebark pine (Pinus albicaulis)
High elevations in the western US and Canada
Keystone species
Mutualistic relationship
with nutcracker
Wildlife dependence
Restoration treatments

18. Example: sudden oak death
First reported in 1995, Marin County
Widespread mortality of coast live oak and tanoak
Numerous other hosts: California bay, buckeye, rhododenron
Phytophthora ramorum: a fungus-like organism (Oomycete).