lecture exam 2 Flashcards
Tussock moths
family erebidae
fuzzy caterpillars with urticating hairs
both native and invasive defoliators in North America
spongy moths
deliberately imported and accidentally released in 1869.
feed on >300 woody plants
tree mortality variable 15% basal area loss; mortality is often delayed.
douglas-fir tussock moths
native species
feed on Douglas fir and true fir species
tree mortality is extensive in mature, heavily defoliated stands.
mortality 20-80%
Brown tail caterpillar
found in Massachusetts in 1897
spread rapidly through the northeast and Canada
has special urticating hairs with strong toxins that can easily break off and go airborne. they remain active in the environment for many years.
by 1914 the species populations went extinct except for 2 small populations in Cape Cod and Casco Bay, Maine.
the population began to spike again in 2015.
Sawflies
belong to the group in Hymenoptera called the symphyta.
bee like adults with chewing mouthparts
some bee and wasp mimics
this group has free feeders, leaf miners, stem borers, wood borers, and a parasitic superfamily.
2 important defoliator families: diprionidae and tenthredinae
DIpronidae
small sawfly family that feeds on conifers.
often colonial with a defensive posture.
aposematic coloration.
tenthredinae
a very large sawfly family of mostly free feeders
Leaf Miners
leaf miners are larval insecrs that live and feed between the epidermal layers of leaves.
most species complete their development within a single compartment of a leaf
~10,000 spp worldwide
evolved independently in many orders including Coleoptera, Lepidoptera, and Hymenoptera
few are major defoliators; most are nuisances or cause aesthetic damage
Invasives: horse chestnut miner, birch leaf miner
native: locust leaf miner, aspen serpentine miner
Effect of defoliation on forests
stand composition: shift in tree species due to mortality and replacement. altered competition balance.
stand structure: dead trees create gaps. mortality may differentially affect size classes creating altered distribution. coarse wood debris. Tree snags.
Bark and ambrosia beetles vs. woodborers
wood borers do not have a complex ecological relationship with the host tree. Bark beetles do and ambrosia beetles tend to be very specialized.
Woodborers primarily feed on non-living xylem tissue
most use dead or dying trees.
species that feed on cambium are more important for tree mortality.
Bark beetles
Scolytinae
feed on phloem
obligate mutualist fungi
mostly conifer feeders
complex communication systems
ambrosia beetles
platypodidae
obligate mutualist fungi
feed on xylem
lack complex pheromones
hardwood and conifer feeders
mycangia
complex cuticular invagination for transporting of symbiotic fungi.
Primary bark beetles
Capable of attacking and killing healthy trees
secondary bark beetles
Attack dead and dying trees including those from primary bark beetle attacks
conifer defense
many conifers are well-defended because they co-evolved with bark beetles.
pitch resin pushes out beetles containing toxins (terpenoids).
hypersensitivity response the cells around a foreign object die or melanize
mass attack
Outbreaks begin when a number of beetles are produced by stressed or unhealthy trees.
as more and more tree beetles attack the tres the effect of resinosis becomes less and less effective allowing more beetles to colonize.
pioneer beetles
select a tree based on many different cues. a pioneer beetle aggregates pheromones to summon more beetles.
tree susceptibility
increases with: drought and warming (reduced beetle mortality)
Semiochemical
chemical messengers. bark beetles produce some of the chemical compounds de novo through chemical synthesis. they akos take conifer phytochemicals and use them as a precursor to other pheromones
pheromones
cause a specific reaction in a receiving organism of the same species.
allomones
evoke in the receiver a reaction that favors the emitter but not the receiver.
kairomones
evoke in the receiver a reaction that favors the receiver but not the emitter.
Emerald ash borer
The emerald ash borer is a green buprestid or jewel beetle native to north-eastern Asia that feeds on ash species. Females lay eggs in bark crevices on ash trees, and larvae feed underneath the bark of ash trees to emerge as adults in one to two years.
feed on: green ash, white ash, black ash
metallic wood boring beetle
bullet shape
serrated head
tucked head
make serpentine gallery
first detected in 2002 outside Detroit
spread to 36 states and 5 provinces
99% mortality of host trees resulting in more invasive
options: tree removal, insecticide, biological control
tetrastichus planipennisi
emerald ash borer parasitoid
Short ovipositor
released in 2007
spathius galinae
emerald ash borer parasitoid
long ovipositor
White pine weevil
Pine and spruce major causes of disfigurement and value loss for structural lumber
adults emerge from the leaf litter in early spring and climb to the top of young conifers
females feed on leaders, creating large egg slits on shoots
larvae hatch and tunnel through the phloem of the leader eventually killing it.
trees are vulnerable for their first 20 years
woodwasp siricidae
specialized family of symphyta - the sawfly
have adapted wood boring and adopted fungal symbionts
2 subfamilies: siricinae and tremecinae
subfamily siricinae
woodwasps and hortails
feed on conifers
most attack dead or dying trees
subfamily tremecinae
Asain Horntails
attack angiosperms
attack mostly dead and dying trees
make extensive tunnels in xylem
may take several years to pupate
genus sirex
multiple species
in the US only a few introduced species
all are associated with conifers
the larval stage gets most of its nutrients from fungi
native species are innocuous and cause little harm.
one European species has traveled all over the world where pines are common and are an added component of the ecosystem that contributes to tree mortality.
Sirex noctilio
one European species has traveled all over the world where pines are common and are an added component of the ecosystem that contributes to tree mortality.
uses a mix of toxins mucous and fungus to suppress the immune system of healthy trees.
in its native range it’s a minor pest.
Sap sucking insects
sap-sucking insects that are of concern are almost entirely from the order Hemiptera.
economically important species are mostly in the order suborder Homoptera like aphids, scale insects, leaf hoppers, delgids, and lanternflies.
cause direct harm from feeding and vectors for disease.
Sapsucker adaptations
1) cibarial pump - works like a siphon to move large amounts of fluid into the esophagus.
2) process large amounts of sweet sticky honeydew
3) specialized symbiotic bacteria for breaking down sap into necessary amino acids
Hemlock wooly adelgid
2 colonization events in North America, one in western NA before the last glaciation, and the other was released by people in the 1950s.
western wooly adelgid had little effect and never became abundant. The eastern wooly adelgid is a major source of mortality for eastern and Carolina hemlock. the eastern wooly adelgids likely came from just 2 females.
Hemlock Wooly adelgid lifecycle
many aphids and adelgids have complex sexual and asexual lifecycles. the sexual generations have wings and can disperse. more complex in their home range (Japan) where they have two host trees.
3 types of HWA: sistentes, progrendientes, sexuparae.
sistentes
adults begin oviposition in late winter and continue laying eggs for a couple of months. these eggs hatch into crawlers which are mobile for a short while before settling and feeding.
- develop flightless progredientes female
- develop into winged sexuparae female
progredientes adult
lay eggs of the sistentes generation mid-may.
sexuparae
the adult flies off in search of a host that doesn’t exist.
Hemlock wooly adelgid feeding
evolved a stylet bundle that is many times longer than its own body to feed on hemlocks. feeds on the parenchyma cells in the xylem, the only living cells in the xylem. naive hemlocks have no defense.
Why are hemlocks important
No other tree can fulfill its ecological role.
long-lived foundations tree creating important habitat. provides habitat for a wide variety of arthropods and vertebrates.
shade tolerant, co-evolved with mixed deciduous forests
mediates soil moisture and stabilizes stream base flow
regulate stream temperature
create cool, moist, microhabitats with a slow rate of N-cycling from the slow decomposition of acidic organic little unique to hemlock-dominated forests.
provides a unique habitat for terrestrial and aquatic ecosystems
other sternorryncha of concern
major pests in horticulture, agriculture and tree plantations but the ones that cause significant harm are mostly invasive.
Green Spruce aphid
native to Europe but now feeds on many NA spruce trees.
wingless adult females continue feeding and producing young parthenogenically through the winter.
in the spring winged aphids are produced and fly to other trees. young nymphs enter diapause during summer and recommence development during autumn.
males are only in their native range. we only have females
Balsam wooly adelgid
Attacks only true firs
native to Eurasia, introduced in 1908
very small: <1 mm
adults and nymphs feed on phloem in the bole and the twigs.
inject chemicals and hormones causing gouty twigs and “rotholtz” in the bole, an abnormal ring compression the inhibits water transport.
increases fir mortality
all are females in NA males only in their native range.
90% fir mortality in northern Appalachia.
