- Foliar Disease
- Overview
- Causes
- Abiotic
- frost, drought, pollution, nutrient def.
- Biotic
- virus, bacteria, FUNGI
- Simplified life cycle (fungus)
- spores released in spring (from leaves infected last year)
- may also have spore build-up in spring/summer
- conifer foliar disease often asymptomatic in year of infection
- Epidemic (wave year)
- lotsa spores
- cool & moist
- susceptible tissue
- tissue age (new thru' epidermis; old thru' stomata)
- phytoplane community (antagonism)
- Checks & Balances
- endemic .. epidemic - discussion topics
- 1. successful infection requires
- a) living spores
- most spores release in few bursts
- b) susceptible tissue
- tissue age
- usu. new - thin cuticle (wax) & epidermis
- older tissue ... usu. stomata
- phytoplane community
- new tissue invaded (not infected)
- antagonism
- c) suitable env. - cool & moist (not hot & dry)
- so ...
- epidemic requires all 3 to coincide
- but ... variation in flushing provides nat. protection (see 3)
- but
- Hw/ Cw have indeterminant growth ... epidemic less likely, but ...
- pine needles elongate most of growing season ... susceptible to foliar outbreaks
- 2. secondary pathogens help collapse an epidemic
- some only infect "already infected sites"
- 19 known pairs in BC
- e.g. L. concolor & H. pinicola
- low L.c. ... H.p. very rare
- L.c. outbreak ... H.p. follows suit
- H.p. inhibits L.c. spores
- L.c. pop'n collapse
- H.p. pop'n collapses too
- 3. genetic variation ... 'resists' epidemics
- a) susceptiblity to infection
- b) again, variation in flushing time
- clones could be very susceptible!
- Conifer: Blight vs. Cast vs. Rust
-
- current (new) tissue (often thru' epidermis)
- premature needle drop (cast)
- from few spore bursts in early spring (young tissue)
-
- all age of needle infected (often thru' stomata)
- needles often held until next year
- infection throughout growing season
-
- alternate hosts
- infection generally close to ground
- white or orange pustules on leaf underside
- broom rusts
- Spruce broom rust
- Fir broom rust
- not considered significant in BC
-
- Damage
- seedlings/ saplings - can be serious (death, growth loss, stress)
- older trees - growth loss
- conifer vs. deciduous
- life of foliage
- ability to releaf mid-season (~3 week delay)
- stored starches in roots (to survive & to releaf)
- Management
- in forest - nothing (except DFS)
-
- D. septosporum DFS (Red Band)
- most destructive needle disease of pines in the world
- affects >60 spp of pines worldwide
- big problem on Radiata Pine in NZ & Chile (introduced)
- in BC
- all pines in BC susceptible
- exotics esp vulnerable
- ... now an issue for Pl in NW BC
- cause ... climate change
- warmer & moister summers
- also along big streams/rivers
- all age needles susceptible
- infection through-out growing season
- warm and moist (rain) is bad
- 1-2 years after infection ... spores
- impact on productivity
- reduced growth, stress (mortality)
- management
- harvest
- don't clearcut in cold air pockets
- planting
- mix spp in M-H hazard
- <20% pine in H hazard
- at JS time
- favour other spp
- but leave Pl as "ghost trees"
- breeding
- shown promise in other areas of the world ... so maybe
- fungicide
- copper-based fungicides used elsewhere
- not in BC
- human health
- produces a toxin closely related to aflatoxin
- its a potential carcinogen
- low risk as needs to be ingested
- Systemic Infection
- "grows with tree" & reinfects new foliage yr after yr
- Snow Moulds
- like low temp & high humid
- spread by external hypha under snow
