Week 4 Flashcards
when did DED become a problem in north america and when in manitoba
In the 1970s
Most eastern north american elms killed by new strain of DED
arraived in manitoba in 1975
what causes DED
the fungus ophiostoma novo-ulmi
what are the symptoms of DED
Yellow flagging (july/august)
Wilting, canopy die-back
Tree death
what does the DED fungus do to trees
Fungus that infects water-conducting vessels (xylem) of tree resulting in blockage
-Seen as staining when bark removed
-Fungus lives in the xylem
how does the DED fungus move between trees
Fungus may move between neighboring trees through root graphs
Bark beetles carry spores from tree to tree
Long distance transmission by humans moving infected wood
how long does the DED fungus take to kill a tree
Tree canopy wilts and tree dies within 1-2 years
what is DED’s vector in manitoba
the native elm bark beetle, hylurgopinus rufipes
what is the life cycle of the native elm bark beetle
May
Beetles emerge from base of tree and fly to feed on healthy elms
Early summer infection from beetles feeding in spring
Yellow flagging as a result
June
Beetles move to dying and dead elms & elm firewood to lay eggs
Brood development
August
New generation of beetles fly to healthy elms to feed
October
Beetles migrate to base of healthy elms over winter
why do elm bark beetles only lay eggs in dead or dying trees
Can only live in dead/dying trees because have to live in floem
Living trees can kill them
how do bark beetles breed and attract mates
Fly to bark of tree and make little tunnel
Release pheromones which attract males
in what pattern do bark beetles lay eggs and what are these galleries called
Make horizontal gallery across bark (maternal gallery)
Eggs laid in gallery
-Hatch in about a week
-Larvae tunnel out parallel to initial gallery (larval gallery)
Whole gallery called brood gallery
when do DED spores transfer to bark beetle larvae
Spore transfer in pupation chamber
Attach to adult who can transport
what do bark beetle larvae do after emergence
Fly to trunks of healthy elms and make feeding tunnels in bark
‘Leapfrog’ down tree and make feeding tunnels lower
Spend winter in lowest feeding tunnel
Emerge next spring and fly to elm canopy to feed
-Transmission of spores
what is the annual percentage elm loss rate in most NA cities
18%
what is the annual elm loss rate in winnipeg
3-4%
what are the 2 main reasons winnipeg loses less elms than other cities
biology and management
when do DED spores enter elm trees
when beetle feeds on thin bark of canopy twigs and spores make contact with xylem
what makes the manitoba vector bark beetle not transmit as many spores as in warmer areas
they aquire DED spores in mid-summer in brood galleries and feeds on canopy twigs in following spring
During this long period
-Many beetles die
-Many beetles lose spores
In vector species in warmer areas
-Beetles emerge as spore-bearing adults and begin feeding in tree canopy immediately
- don’t have to wait till spring
what are some things we do to manage DED
Limit movement and storage of elm wood
Remove unhealthy elm trees
No pruning of elm trees april-july
Diversification of urban forest
Periodic injections of fungicide into specimen trees
Remove infected elm trees
Manage beetle populations
how are infected elm trees removed
Surveys conducted in july and august
Symptomatic trees tagged
Tagged trees removed following winter to prevent transmission
should infected elm trees be removed rapidly or the following winter and why - what are the trade offs
Beetles can leave newly-diseased trees before winter removal
Rapid removal associated w/ lower infection rates
Difficult to implement in large municipalities
how have beetle populations been managed historically
Spraying bases of boulevard elm trees with insecticides to kill overwintering beetles
- used chlorpyrifos
what is the history of chloryprifos spraying for managing beetle populations
In 1970s most canadian used chlorpyrifos
By 2001, most cities had no elm trees
Basal spray not economic
Winnipeg can’t use for turf insects
By 2023 chlorpyrifos banned due to unsupplied safety data
Insects can no longer be managed by basal spraying
where should basal spraying be done on trees to manage beetle populations
Recommended basal spraying be done on lower 50cm of trunk of tree more than 10cm in diameter
can beetles detect trees with DED before humans
Fungus causes tree to send out volatile chemicals in june that attract breeding beetles before we see symptoms
beetles need dying trees to breed
when do beetles emerge from newly infected trees after larvae and how many contain spores
Late august and september
91% carry spores
how many elm trees has winnipeg kept
Of its original 600,000 American elm trees, Winnipeg has retained about ⅓ after 48 years of DED, which is an excellent track record.
do all infected elm trees contain many beetles
no, 20% contain 90% of beetles
how to identify infected elm trees for rapid removal
Should itdentify 20% of trees with most beetles
Rapid removal would remove 90% of beetles and feasible
Remove remaining trees over winter
Indicators based on canopy inspections
what are some of the definining characters of beetles (coleoptera)
Hardened forewings called elytra
Biting, chewing mouthparts
Holometabolous
why are elytra useful and whats under them
Membranous hind wings, concealed under elytra when at rest
Protected by elytra
Allow beetles to live in rugged environments
what are some defining features of ground beetles
Antennae thread-like, 11 segments
Prothorax is middle compartment
Elytra cover all of abdomen and meso and meta thorax
5 tarsal segments on all legs
where are ground beetles found
Occur from manitoba and minnesota south and east to the atlantic coast
Live on lakeshores and river banks w/ limestone slabs
Adults hide under stones during day
when are ground beetles active
Adults active on surface at night
what is the difference between male and female ground beetles
Male
Front tarsi flattened and broadened
Needed to grip females when mating
Female
Front tarsi cylindrical
how can you tell how old a ground beetle is
new beetles
Look shiny
Old beetles
Look dull from going around rocks
where do ground beetles lay eggs
cemented to rocks
what are some parts of a ground beetles larvae
Head capsule
Thorax w/ 3 pairs of legs
Long abdomen
Urogomphi
-Little things stick out back of abdomen
Anal tube
-Used to secrete glue and hold onto rocks
how can you determine what instar a ground beetle larvae is in
Larval instar determined by width of head capsule
what is dyars rule
Ratios of dimensions of sclerotized organs of adjacent instars are relatively constant
what do ground beetle pupae look like at different stages
New pupa with larval exuvia
Small eye spots
Close to time of adult emergence
Bigger eyes, pigment on parts
what are ground beetles like after emergence from pupa
Very fragile and get harder over time
what is the seasonal pattern of ground beetles in manitoba
Dull adults in may
Mating in june/july
-Larvae appearing
New generation appear in august and disappear in september
what do ground beetles eat mid-summer
diet dominated by fishflies (ephemeroptera)
They live and develop under lake
Emerge above lake and casts exuvia
-Dead adults
-Exuviae from emergence
-Blowfly larvae feeding on above
what do ground beetles eat in spring and late summer
Fragments of other insects found in gut
why is the lake useful for finding food
Lakes conveyor belts bringing food to beach-dwelling insects
Insects falling from above
-Fall in lake and wash up on shore
Emerging from lake bottom
where do ground beetles go in september
Beetles aggregate in gravel mixed with leaf litter at top of beach
-Where wind blows leaf litter, wind blows snow
how do ground beetles get food in winter
Frozen lakes also conveyor belts
-Snow blows off ice and accumulates at top of beaches
-Same place adults aggregated
are ground beetles freezing tolerant or intolerant and why
Does not survive freezing but doesn’t freeze at temperatures above -7c
-Antifreeze in blood
where do ground beetles stay over winter
Relies on finding protected winter habitats for for winter survival
-Under snow where it is warmer
-Why they don’t live on riverbanks as much (not as much snow)
how do ground beetles know when to start entering reproductive state
Day length is cue that initiates reproductive physiology
how do carabid beetles defend themselves
heavily armored and use chemical defences
what is the pygidium and where is it located on a carabid beetle
Pygidium (end bit)
Abdominal segments 7-10 of carabid beetles
Normally somewhat hidden (tucked in)
what are the pygidial glands and where are they located on a carabid beetle
glands that produce defensive chemicals
located on pygidium
what are some parts of the pygidial glands in general for carabid beetles
Secretory lobes
Secrete liquid into collecting canal
Collecting canal
Puts liquid into reservoir
Muscular reservoir
Where liquid is reserved for use
Efferent duct
Where muscular reservoir liquid goes out of
what is special about caradbid beetles with thin walled resevoirs
excretion oozes on the surface of beetle
Makes beetle distasteful
Outlet is a simple pore in abdominal surface
how do beetles with muscular reservoirs excrete chemicals
Can forcibly contract
Sprays secretion for tens of centimeters
Outlet can be extruded into a nozzle
aim spray towards enemy
what is the typical chemical composition of a carabid beetle irritant
> 90% irritant and <10% surfactant
what is a surfactant and why do carabid beetles have it in their chemicals
Surfactant is material that causes liquid to spread over surfaces
Spreads out irritant and spreads over surface of beetle
what is the most common form of irritant in carabid beetles
formic acid
what kind of irritant do harpalus use
Defensive secretion 95% formic acid
MSDS for formic acid
Very hazardous for skin contact, eye contact or ingestion
Skin contact produce burns
Liquid or spray mist may damage mucous membranes of eyes, mouth and respiratory
Inhalation of spray mist produce severe irritation of respiratory, coughing, choking, shortness of breath
what kind of irritant do pterostichus use
90% methacrylic acid
MSDS for methacrylic acid
Hazardous irritant for skin, eye, ingestion, inhalation
what kind of irritant do Chlaenius cordicollis (manitoba ground beetle) use
96% 3-methylphenol
MSDS 3-methyphenol
Very hazardous for skin contact, eye contact, igestion, inhalation
what type of irritant do brachinus (bombardier beetle) use
100% quinones
MSDS for quinones
Extremely hazardous for eye contact
Very hazardous for skin contact, inhalation
what kind of irritant does Anthia, the oogpister beetle use and how does it work
Formic acid in directed spray
Project by muscular reservoir
Not directly from ant food
Aposematic (warning) colouraction
Mimicry
Other species mimic
how far can bombardier beeetle spray
explosively 20cm
what do the accessory glands do in a bombardier beetle
Secrete enzymes
Catalase & peroxidase
Changes irritant to very potent one and produces heat
what happens in a bombardiers explosion chamber
Heat releasing chemical reaction in reaction chamber (100c)
Benzoquinone
Pressure release valve
When not under pressure its closed
Enough pressure valve opens
what are the steps for bombardier beetle to spray acid
- Inlet valve opens, charging reaction chamber
- Valve closes, enzymes are released
- Heat-producing reaction brings liquids to boil
- Pressure increase opens pressure relief valve
- Reduced pressure causes steam explosion
- Spray is released through aimed nozzle
- Temperature and pressure drop, relief valve closes
- Repeat steps 3-7 about 500 times/second
- Repeat steps 1 and 2 when necessary
what kind of irritant secrestion does chlaneius cordicollis have
Muscular reservoirs that can spray secretion 30cm
3-methyl phenol
what else can chlaenius cordicollis use irritant secretion for
Evidence defensive secretion also used in sexual communication
why do carabid beetles use defensive chemicals for other functions
metabolically expensive to produce
