Transcript Exotic insects and pathogens: ecology and management

Forest insects and pathogens:
ecology and management
by
Kristen Baker
Insect Feeding categories
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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
Biotic causes of plant
disease
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Fungi - most common
Nematodes
Bacteria
Viruses
Protozoa
Parasitic plants
The Disease Triangle
Pathogen
Environment
Amount of Disease
Host
Management and control
options
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Chemical
– DDT, copper sulfates, botanicals
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Biological
– use of one organism to control adverse effects
of another (natural enemies such as insect
predators, viruses, pathogens)
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Cultural
– active management of vegetation to prevent or
reduce damage or decrease pest population
Integrated pest management
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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
Native insects and
pathogens
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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)
Example: bark beetles
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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
Example: root diseases
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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 nonsusceptible species to establish in
forest
Exotic insects and pathogens
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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
Example: balsam woolly
adelgid
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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.
Management and control
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Biological control
– insect predators, pathogens
– limited success to date
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Environment
– cold winter temperatures
– early or late frost
Example: white pine blister
rust
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Introduced from Europe ~1900
Infects all 5-needled pines: sugar
pine, eastern and western white pine,
whitebark pine
White pine blister rust
Whitebark pine (Pinus albicaulis)
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High elevations in the western US and
Canada
Keystone species
Mutualistic relationship
with nutcracker
Wildlife dependence
Restoration treatments
Example: sudden oak death
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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).