Lecture 19 Flashcards
what is the name of the fungus in dutch elm disease?
Ophiostoma novo-ulmi
where do infections seem to occur?
near streams - method of infection is having dead logs move along streams
what is the initial sign of infection? & then what happens?
yellow flagging in July/Aug
Wilting, canopy dies
Yellow leaves are wilted & dead
All of the leaves can die in a month
leads to tree death
what does the fungus infect?
water-conducting vessels (xylem) of the tree resulting in blockage
xylem
conducting tissue that carries water up the tree of the roots
inner bark/wood
phloem
carries sugar solution down the tree from the leaves (product of photosynthesis)
outer bark
how does DED cause the tree to die?
wilt disease preventing water to reach the canopy
Tree will block the vessels of the xylem to prevent the disease from spreading, which will also prevent the water from spreading to the canopy
where does staining occur during infection?
xylem
how does DED spread?
Bark beetles carry spores from tree to tree
describe the lifecycle of bark bettles
October – Beetles migrate to the base of healthy elms to overwinter
Create tunnels in the tree & spread the spores
May – Beetles emerge from the base of the tree & feed on healthy elms
Look for food, fly to the top of the canopy of elm trees
Feed on bark & transfer the spores to the xylem
June – Beetles move to dying & dead elms & elm firewood to lay eggs
August – 7-8 weeks of development, new beetles then move to healthy elm trees
Will feed
Move down tree to overwinter
describe the breeding process of bark beetles
arrive in June, females arrive first
Females make a hole, go under the bark & reach phloem Release pheromone to attract males
describe the egg production process of bark beetles
females leave a horizontal line behind their tracks & lay eggs
describe the larval growth process of bark beetles
larvae tunnel is perpendicular to maternal tunnel (across grain)
Produces a characteristic pattern
brood gallery
maternal & larval gallery (tunnel paths)
Galleries enable detection of beetles what is there? & what was there? Occurs in phloem
frass
fecal matter
what occurs at the end of the gallery?
there is a plug of frass where the larvae have traveled
Creates a cell
Turns into a pupa & then an adult
At this time the fungus invades the phloem with fruiting bodies where the galleries exist When the adult has formed, the spores are now stuck to the outside of the beetle
The spores attached during other life stages don’t matter b/c they will be shed with molting
what occurs when the beetles emerge?
Beetles fly to trunks of healthy elm trees & make feeding tunnels in the bark
“Leapfrog” down & make tunnels lower on the same tree
why do beetles feed on the outside of healthy trees?
Healthy trees can produce resins which kill the beetles
where do the beetles spend winter?
in the lowest tunnel
Few beetles overwinter on trees less than _____ diameter, max of ______ diameter
10cm
20cm
why does the tree need to have proper thickness?
burrowing &
protection during overwintering
few beetles overwinter _____ above the ground & _____ below the ground
15cm
10cm
what beetles escape the effect of insecticides?
those who overwinter under ground
how do beetles survive when living underground?
most of these will have fed above ground near the base of the tree
how are beetles attracted to the trees?
Fungus manipulates chemicals given off by the tree – since there is fungus present, the tree no longer has its defense mechanism of resin to kill the beetles
why does the fungus attract beetles?
so it can spread it’s spores
when do adults emerge from newly-infected trees?
Aug-Sept
Does delaying removal until winter result in higher infection rates?
yes
should rapid removal be adopted?
yes, assoc with lower infection rates
Can counting galleries on trunks of DED-infected trees identify “super-shedders”?
YES
correspondence of numbers in trunk samples & the total #s per tree
trees with no galleries had low #s overall
