Forest insects and pathogens: ecology and management

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Forest insects and pathogensecology and
management

• by
• Kristen Baker

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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

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Biotic causes of plant disease

• Fungi - most common
• Nematodes
• Bacteria
• Viruses
• Protozoa
• Parasitic plants

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The Disease Triangle
Amount of Disease
Pathogen
Environment
Host
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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

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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

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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)

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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

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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

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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

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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.

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Management and control

• Biological control
• insect predators, pathogens
• limited success to date
• Environment
• cold winter temperatures
• early or late frost

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Example white pine blister rust

• Introduced from Europe 1900
• Infects all 5-needled pines sugar pine, eastern
  and western white pine, whitebark pine

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White pine blister rust
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Whitebark pine (Pinus albicaulis)

• High elevations in the western US and Canada
• Keystone species
• Mutualistic relationship
• with nutcracker
• Wildlife dependence
• Restoration treatments

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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).