Tree pathology questions

is tree pathology on important ecologically

no! it’s also important economically (the timber business)

what are some abiotic disease agents

• nutrient deficiency

• temperature extremes

• drought

• sunlight damage

• air pollution

what are some biotic disease agents

• viruses

• bacteria

• fungi

• insects

• parasitic plants

which of the biotic disease agents are the greatest threat to forests

viruses, fungi, and insects

what is the most numerous and destructive agent of tree disease

fungi

how do fungi spread disease

they secrete enzymes that digest their substrate and then absorb leftover nutrients

what are examples of foliage diseases

leaf spot pathogens, anthracnose, and needle blight

what is leaf spot pathogens caused by

mostly fungi, but can be caused by bacteria and viruses

can needle blight defoliate entire trees? how?

yes it can! the blight manifests as dark bands around needles that kill the leaf from there to the tip

do rust diseases impact certain life stages of trees more

yes, it’s especially hard on seedlings and saplings

explain how white pine blister rust infects

a fungus grows into the stem and sporates, forming orange blisters on twigs. spores are released from the tree and infect ribes leaves. spores are relesased from spots on ribes leaves, and go back to infect pine needles, starting the process again

which are more deadly: leaf or stem diseases

stem diseases

what are some examples of stem diseases

wilt and stain fungi

canker diseases

stem decay

dutch elm disease and oak wilt disease are carried by what vectors

insect vectors

how do trees form cankers

the tree forms callous tissue in response to the fungi, leading to a swollen area on the stem

the fungus causes dead sections of bark on trunk

what caused the chestnut blight and how did it impact chestnut trees

• caused by Cryptonectria parasitica

• introduced with asian chestnuts

• wiped out nearly all chestnuts in Easter North America (though small trees/sprouts still exist)

does stem decay have a big impact on tree health

no it’s usually minimal

what do the fungus of stem decay form

they form conks (shelf fungi)

how does stem decay impact wood value

it has a big negative impact

how can root diseases spread

through grafted roots

how does root disease impact the tree

it reduces vigor and can kill trees

what is interesting about armillaria root disease

it lives on multiple species both in tropical and temperate forests

it’s a facultative saprophyte, meaning it can live on live and dead roots/wood, allowing it to kill the tree

what are the types of insect pests and diseases

defoliators, bark beetles, wood borers, sucking insects, shoot/bud insects, root insects

explain the defoliator gypsy moth

it’s an introduced pest of more than 500 host species

often found on aspens and oaks

accidentally introduced by Edward Lee Trouvelot near Boston in 1868

explain how tent caterpillars and web worms are defoliators

• they are moths that build webs as larvae that are made of silk

• usually don’t ahve a strong impact on healthy trees

• they target broadleaved angiosperms, not conifers

• ex. eastern tent caterpillar and fall webworm

  • both native and generalists

what kind of trees do bark beetles target

they attack already stressed trees that can’t “pitch” (sap) them out

can bark beetles kill trees

yes! they make galleries (tunnles in the bark) and these can eventually girdle the tree, killing it

give more details about emerald ash borer

• it was introduced to NA in 2002 and spread to 38 states so far

• it’s host specific, so it only feed on Fraxinus (ash) and sometimes related genera

• mortality rate for large treees is almost 100% within 6 years

what can be considered a wood borer and what do they usually attack

they can be beetles, wasps, and sometiems moths (all in larval stage tho)

they usually attack stressed trees, since their defences are down

what can sucking insects do to the tree

they can damage or kill the tree, and also introduce pathogens

explain how hemlock woolly adelgid was introduced and how they threaten hemlocks

• they’re introduced and invasive

• native to japan

• introduced in NA in Richmond, VA in 1951

• only recently found in Erie because cold climate had been keeping them from establishing but climate change is changing that

• kills hemlocks in 4-10 years, and threatens to seriously alter forests that hemlocks dominate (needles make the floor acidic, thus the composition would change)

Explain how dutch elm disease is a complex interaction

There are two organisms that are needed to spread the diseas:

1. Ophiostoma species - exotic wilt fungi (>1 spp) that aggressively grow in and kill native elms - it can’t disperse it’s own or penetrate intact trees

2. native elm/european/banded bark beetle (2nd and 3rd are introduced spp) - bark beetles spread spores from tree to tree as they eat in the xylem where the fungus lives

both organisms cause problems, and is why they’re not considered vectors (vectors don’t cause problems, just transmit pathogens)

what are some abiotic and biotic agents that are apart of sugar maple decline

• water stress from drought

• defoliation from gypsy moth

• canker fungus

• sugar maple borer in xylem

• fungal pathogen in vascular tissue

• armillaria root rot

• root damage from harsh winters and nematodes