Lecture 19

Question 1

what is the name of the fungus in dutch elm disease?

Answer 1

Ophiostoma novo-ulmi

Question 2

where do infections seem to occur?

Answer 2

near streams - method of infection is having dead logs move along streams

Question 3

what is the initial sign of infection? & then what happens?

Answer 3

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

Question 4

what does the fungus infect?

Answer 4

water-conducting vessels (xylem) of the tree resulting in blockage

Question 5

xylem

Answer 5

conducting tissue that carries water up the tree of the roots

inner bark/wood

Question 6

phloem

Answer 6

carries sugar solution down the tree from the leaves (product of photosynthesis)

outer bark

Question 7

how does DED cause the tree to die?

Answer 7

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

Question 8

where does staining occur during infection?

Answer 8

xylem

Question 9

how does DED spread?

Answer 9

Bark beetles carry spores from tree to tree

Question 10

describe the lifecycle of bark bettles

Answer 10

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

Question 11

describe the breeding process of bark beetles

Answer 11

arrive in June, females arrive first

Females make a hole, go under the bark & reach phloem

Release pheromone to attract males

Question 12

describe the egg production process of bark beetles

Answer 12

females leave a horizontal line behind their tracks & lay eggs

Question 13

describe the larval growth process of bark beetles

Answer 13

larvae tunnel is perpendicular to maternal tunnel (across grain)
Produces a characteristic pattern

Question 14

brood gallery

Answer 14

maternal & larval gallery (tunnel paths)

Galleries enable detection of beetles  what is there? & what was there?

Occurs in phloem

Question 15

frass

Answer 15

fecal matter

Question 16

what occurs at the end of the gallery?

Answer 16

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

Question 17

what occurs when the beetles emerge?

Answer 17

Beetles fly to trunks of healthy elm trees & make feeding tunnels in the bark

“Leapfrog” down & make tunnels lower on the same tree

Question 18

why do beetles feed on the outside of healthy trees?

Answer 18

Healthy trees can produce resins which kill the beetles

Question 19

where do the beetles spend winter?

Answer 19

in the lowest tunnel

Question 20

Few beetles overwinter on trees less than _____ diameter, max of ______ diameter

Answer 20

10cm

20cm

Question 21

why does the tree need to have proper thickness?

Answer 21

burrowing &

protection during overwintering

Question 22

few beetles overwinter _____ above the ground & _____ below the ground

Answer 22

15cm

10cm

Question 23

what beetles escape the effect of insecticides?

Answer 23

those who overwinter under ground

Question 24

how do beetles survive when living underground?

Answer 24

most of these will have fed above ground near the base of the tree

Question 25

how are beetles attracted to the trees?

Answer 25

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

Question 26

why does the fungus attract beetles?

Answer 26

so it can spread it’s spores

Question 27

when do adults emerge from newly-infected trees?

Answer 27

Aug-Sept

Question 28

Does delaying removal until winter result in higher infection rates?

Answer 28

yes

Question 29

should rapid removal be adopted?

Answer 29

yes, assoc with lower infection rates

Question 30

Can counting galleries on trunks of DED-infected trees identify “super-shedders”?

Answer 30

YES

correspondence of numbers in trunk samples & the total #s per tree

trees with no galleries had low #s overall