Forest insects and pathogens: ecology and management

1. Forest insects and pathogens:ecology and management by 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).