fun guys exam 1

plant disease definition

Any deviation from the normal function of a plant that

threatens its health or survival or decreases its aesthetic

or economic value as a whole or any of its parts

plant disease triangle

pathogen, environment, host

fungi characteristics

1. heterotrophs that absorb nutrients

   1. utilize organic matter for carbon

   2. need water, nitrogen, light, proper temps

2. have a number of different cell types

3. can be difficult to identify and classify

hyphae definition

long slender filaments of multicellular fungi

mycelium definition

mass of connected hyphae

how do fungi obtain food

secreting digestive enzymes into their substrates— external digestion
allows them to break down cellulose and lignin (and sometimes animals)

how are the carbon needs for fungi met (2 options)

1. parasitism of plants or animals, causing disease

2. saprophytism: growing on dead animal, plant, or microbial biomass

pathogen definition

agent that causes disease

endophyte:

live inside tree organs such as leaves or xylem but cause no damage

latent infection

the time between the infection and symptom expression

why is the disease triangle helpful

it emphasizes that disease and pathogen are not the same thing and that disease is caused by a mixture of factors

sign meaning

physical appearance of a pathogen

symptom meaning

alterations in the appearance of the host due to disease

infected meaning

plants or plant parts that a biotic pathogen has entered

infested meaning

areas, stands, plots, soils, containers, etc where pathogen is present

fungi characteristics:

• basic structural unit is almost always a hypha

• reproduction propagule almost always a spore

• nutrition is heterotrophic and absorptive

Oomycota

• technically not kingdom Fungi

• water molds

Ascomycota

• 8 spores in ascus sac that are forcibly discharged

• includes so many

Basidiomycota

• sexual spores

• many have septal structures that clamp connections during most of the life cycle

Agaricomycotina (subphylum)

• inlcudes conks and puffballs

• the basidia are aseptate and spores germinate to give only hyphae

life cycle of basidiomycete

spores are spread by wind
spores germinate (if they land somewhere good)
when sexually compatible germlings grow nearby, their hyphae fuse and mix cell content (plasmogamy)
If conditions allow, produces fruitbody for sexual reproduction and dispersal

control vs management

control: reduction of disease to zero
management: not total control

silviculture for disease management

• thinnings help remove diseased individuals

• planting or favoring resistant species

• choosing management style based on disease

breeding for disease management

• duh

r selected plants

• rapid growth

• dominate disturbed areas

• invest in reproduction

K selected plants

• cope with heavy competition

• long term srvival

• defense against herbivores and pathogens

ash dieback hosts

most european ash highly susceptible, Asian ash more tolerant

ash dieback pathogen

Hymenoscyphus fraxineus

ash dieback environment

moist, cool sites

ash dieback disease cycle

• ascospores produced on fallen leaves

• they are fired upwards and wind dispersed

• infects leaf, causes necrosis

• moves into shoot if leaf is not dropped

• if leaves are shed, they restart cycle

ash dieback signs and symptoms

• small brown lesions on leaves that become large black and necrotic

• cankers on shoots

• diamond shaped cankers on stem around branches

• wilting and branch dieback

ash dieback distribution

• native to asia

• introduced to europe, killed 80% of young ash in norway

swiss needle cast hosts

• douglas fir that’s it

• dense young stands

swiss needle cast pathogen

• Nothophaeocryptopus gäumannii

swiss needle cast environment

• moise

• young, dense stands like Christmas tree plantations

• epidemic in Oregon

swiss needle cast symptoms

• needles become yellow-green, chlorotic, then mottled or brown, then fell

• thin crowns, particularly in lower inner foliage

• lines in stomata on needles

powdery mildew of flowering pear environemnt

free moisture on leaf surface NOT required

xylem location and purpose

inner bark transport water

phloem location and purpose

outer bark, transport nutrients

mechanisms of wilting

• plugging by mycelium and spores

• plugging by gels, gums from cell wall breakdown

• parenchyma cells may produce tyloses- blocks pathogen invasion but also blocks water flow

dutch elm disease pathogen

Ophiostoma ulmi

dutch elm disease spread

beetle inoculates tree during feeding, beetles breed in infected dying tree

oak wilt pathogen

bretziella fagacearum or something

most and least susceptible groups to oak wilt

red oaks most
white oaks least

oak wilt environment

disease progression favored by hot dry conditions, disease transmission favored by cool moist condistions

oak wilt treatment

• trenching

• avoid pruning in spring and summer

• treat wounds

mistletoe genus

viscum

what hype of parasite is mistletoe

hemiparasite and obligate parasite- takes water an inorganic nutrients from host but makes organic food

how does mistletoe affect host plant

kills them by using all their water

canker definition

infection disease of the phloem and cambium on stems, branches, or twigs of trees

what causes cankers

mostly Ascomycota