Foliage Diseases and Rusts

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Foliage Diseases and Rusts
Reading Text, Chapter
13 Some slides provided by Daniel Omdal
Forest Pathologist Department of Natural
Resources Olympia, WA
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FOLIAGE DISEASES - caused by
Ascomycota RUSTS - caused by Basidiomycota
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A. FOLIAGE
DISEASES 1. General life cycle - foliage diseases
are caused by Ascomycota. Typically produce
sexual ascospores in spring to infect new foliage
and asexual spores (conidia) during the rest of
the growing season. A few produce ascospores in
fall. Both spore stages may not be produced.
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Inoculation
Germination
Dissemination
(Asexual)
Reproduction
(Sex)
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Tar spot on maple
Common hardwood foliage diseases - tar spots,
leaf spots, sooty molds, powdery mildews, etc.
Also sycamore and dogwood anthracnose (infect
leaves and twigs).
Leaf spot on aspen
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Discula sp. on C. nuttalii
Dogwood Anthracnose
Sycamore Anthracnose
Apiognomonia sp. on Platanus
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• 3. Common conifer needle diseases in the Pacific
  Northwest
• Douglas-fir
• i. Rhabdocline pseudotsugae causing Rhabdocline
  needle cast.
• ii. Phaeocryptopus gaeumanii causing Swiss
  needle cast
• b. Pines
• Elytroderma deformans causing Elytroderma needle
  cast - ponderosa and Jeffery pines
• Mycosphaerella (Dothistroma) pini causing red
  band needle blight - ponderosa, bishop, Monterey
  pines - important in exotic plantations in the
  southern hemisphere.
• c. Larch needle blight caused by Hypodermella
  laricis

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Rhabdocline Needle Cast on Douglas-fir
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Disease History
Swiss Needle Cast

• First described from Douglas-fir in Switzerland
  in 1925 as Adelopus sp.
• By 1927, the same fungus was identified on
  Douglas-fir in England and Ireland (distinct from
  Abies, so named gaeumannii and tagged SNC)
• 1938 surveys confirmed that the fungus was widely
  distributed throughout the PNW

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History (cont.)

• Herbarium specimens placed the fungus in Oregon
  as early as 1916
• By 1940, SNC had been identified in six
  northeastern states
• SNC discovered on the North Island of New Zealand
  in 1959

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History (cont.)

• By 1970, SNC reported on Christmas trees in MI
  and WI
• By the mid 1970s, Christmas tree growers in the
  PNW began reporting damage caused by SNC
• By 1990, SNC began appearing in forest
  plantations along the Oregon coast

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SWISS NEEDLE CAST ON DOUGLAS-FIR
Fruiting bodies (pseudothecia) plugging
stomates
Heavily infected tree with loss of foliage
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Cross section of Douglas-fir needle revealing
stomate fully occupied by pseudo- thecia of P.
gaeumannii
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Foliage Disease Management Cultural -
thinning to increase wind movement and reduce
canopy moisture use correct seed sources and
tree species. Fungicides generally not used in
Pacific Northwest except in Christmas trees.
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SNC- Silvicultural Recommendations
Damage Severity
Medium
High
Low
Clearcutting
At appropriate economic point
A.S.A.P
When desired
Uneven-age silviculture
Encourage non D-f species
Encourage non D-f species
Encourage non D-f species
Can use chlorothalinol fungicide Fertilize with
sulfur and nitrogen
needle retention low 2.6-3.5, medium
1.6-2.5, high lt1.5 yrs.
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Elytroderma needle cast
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Mycosphaerella (Dothistroma) needle blight
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Larch Needle blight and cast
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• B. RUSTS
• Rust life cycles
• - long cycle rusts (2 hosts) - pycniospores and
  aeciospores on one host, urediniospores,
  teliospores and basidiospores on other host.
• Example -white pine blister rust
• short cycle rust (1 host) - typically aeciod
  teliospores can infect same host
• Example -Western gall rust

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RUST SPORES STAGES Spore
type Structure Host Spermatia Spermagon
ium Host 1 (pynciospores) (Pycnium) Aeciospores
Aecium Host 1 Urediniospores Uredinium Host
2 (Uredospores) (Uredium) Teliospores Telium
Host 2 Basidiospores Basidium Host 2
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2. Important rusts a. White pine blister rust
caused by Cronartium ribicola (an introduced
fungus) - economic host - 5 needle pines -
alternate host is Ribes spp. (currants and
gooseberries). b. Western gall rust - caused by
Endocronartium harknessii economic host shore
pine and lodgepole pine - no alternate host
(short cycle rust). Native pathogen. c. Poplar
rust - caused by Melampsora spp. economic host
poplars, especially hybrid poplars - alternate
host conifers, particularly Douglas-fir - several
species of Melampsora are involved (some
introduced). d. Fusiform rust - caused Cronartium
quercuum f. sp. fusiforme economic hosts slash
and loblolly pines in SE USA - alternate host
oaks - native pathogen..
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• White pine blister rust was introduced from
  Europe into eastern North America in late 1890s.
• Introduced into Vancouver, British Columbia in
  1910 on a shipment of eastern white pine
  transplants from France.
• Native to Asia and has now invaded the range of 5
  needle pines in North America and is still
  spreading.
• The alternate hosts are Ribes spp. (currants and
  gooseberries) and new hosts.
• Little resistance in North American 5 needle pine
  populations.
• In western North America C. ribicola has spread
  throughout the North Rocky Mountains, the Cascade
  Range and the Sierras. There are isolated
  populations in New Mexico, Nevada, Utah and
  Colorado.

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Allen et al. 1996. Common tree diseases of BC
White pine blister rust
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WHITE PINE BLISTER RUST
Allen et al. 1996. Common tree diseases of BC
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White pine blister rust - causing mortality in
white bark pine at Crater Lake
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Western gall rust, a native disease caused by
Endocronartium harknessii, has generally not been
a problem in the past. However, with recent
intensive management of lodgepole pines where
large areas of young trees are regenerating in
inland western North America young trees have
become severely infected. Gall formation
severely distorts growth, kills branches and can
even kill trees. This disease can also be a
problem in forest nurseries. Short cycle rust.
Rust infects from pine to pine.
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Western gall rust
Allen et al. 1996. Common tree diseases of BC
Aeciod teliospores
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Poplar rust
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• In contrast to Cronartium ribicola, Cronartium
  quercuum f. sp. fusiforme the cause of fusiform
  rust is a native pathogen, with oak species as
  alternative hosts.
• Little impact before 1930, but now the most
  important disease in the SE USA.
• So what happened to make it so important in a
  region where the fungus had evolved with the
  hosts? Rreasons related to forest management
  include
• (1) fire control - oaks are more sensitive to
  fire than pine, so fire control has increased the
  abundance of oaks,
• (2) off site planting of slash and loblolly pine
  in areas where resistant longleaf pine used to
  grow,

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• 3) thinning and fertilization increased growth of
  southern pines, but made them more susceptible to
  rust infection,
• (4) genetically superior trees were selected only
  for growth not for rust resistance,
• (5) seeds from infected trees were used for early
  plantings, and
• (6) infected seedlings from nurseries were widely
  planted.

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Stem cankers on southern pine. Stems can break
at cankers
Uredinia on an oak leaf (alternate host)
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Management of Rust Diseases A
number of strategies can be used to manage rust
diseases, including (1) quarantine, (2) genetic
resistance, (3) identification of high hazard
areas, (4) correct nursery practices, (5)
management of the alternate host (Ribes
grubbing), (6) thinning and pruning, (7) Control
burning for fusiform rust, (8) fungicides. Had
quarantine been practiced in the early 1900s,
white pine blister rust probably would not have
spread so easily.
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Breeding white pine for blister rust resistance
Seed orchard for producing blister rust resistant
white pines
Rust resistance test in the field