root rots: phytophthora that attack the fine feeder roots...
TRANSCRIPT
Root Rots: Phytophthora that Attack
the Fine Feeder Roots of Trees
Symptoms •Damping off (seedling diseases)
Preemergence = death of seedling before hypocotyl emerges
Postemergence = death of seedling after emergence from soil
•Stem canker
•Chlorotic foliage
•Wilting
•Shoot dieback
•Stunted growth
•Collar rot
Root rot Post-emergence damping off
Damping off of Seedlings
Control – Cultural - Reduce irrigation
Chlorinate irrigation water
Plant on raised beds
Plant in porous potting mixtures
Plant during weather that favors
seedling growth
– Chemical - Fumigate soil (methyl bromide)
Do not over fertilize
Diseases caused by Phytophthora
Little Leaf Disease of Shortleaf Pine -
Phytophthora cinnamomi
Ohia Decline
Jarrah Decline
Root Rot of Port Orford Cedar-
Phytophthora lateralis
Sudden Oak Death - Phytophthora ramorum
Oomycetes (Water Molds) Fungus-like organisms, but more closely related to brown
algae
Asexual Spores -Zoospores : Motile with two flagella
Form in sporangia (zoosporangia).
Chlamydospores: asexual thick-walled
survival spores.
www.botany.hawaii.edu
• Sexual Spores
Oospores - spherical thick-walled survival structures
Diseases Caused by
Phytophthora cinnamomi
• Littleleaf Disease – Hosts = short leaf pine, southeastern USA
– Symptoms = sparse foliage, chlorotic needles, dieback,
death in 3-10 yrs
– Zoospores attacks feeder roots under wet conditions
Control = remove diseased trees, replant to non-host, do not
plant trees on sites that will cause stress (e.g. poorly
drained sites), fertilize landscape trees
Littleleaf Disease and P. cinnamomi in the Southeast
1. P. cinnamomi introduced into the SE
200+ yrs ago
2. Killed lots of chestnut (ink stain
disease of roots)
3. Shortleaf pine was planted extensively
4. P. cinnamomi killed shortleaf pine
especially over former chestnut range
Phytophthora cinnamomi
Ohia Decline in Hawaii
• Root rot of Ohia Forests
– Symptoms = forest decline
– Wet sites with decreased drainage
Phytophthora cinnamomi
Jarrah Decline
• Jarrah Decline – Hosts = Eucalyptus marginata (Jarrah); Also attacks 50-
75% of southern Australian forest species
– Symptoms = chlorosis and necrosis, stunted leaves, wilt, dieback, mortality
– Zoospores attack fine roots, especially in soils with a hardpan layer
– Control = quarantine, apply fungicide to vehicles moving through diseased zones, prevent entry of the pathogen in disease free areas (vehicles, people, livestock)
Root Rot of Port Orford Cedar Caused
by Phytophthora lateralis
Root Rot of Port Orford Cedar Caused
by Phytophthora lateralis
– Host = Chamaecyparis lawsoniana
– Symptoms = inner bark discoloration, root rot,
girdling of tree base, chlorotic/necrotic foliage, death
– Zoospores attack fine roots, hyphae spreads through
inner bark
– Severe epidemics along streams and roads
– Control - Prevent spread! Search for and plant
resistant trees
Sudden Oak Death
Coast live oak and tan oak
in California
P. ramorum life cycle
Asexual – Sporangia produce zoospores
Chlamydospores
Sexual Stage – Oospores not found in
US
Phytophthora ramorum causes deadly cankers
and foliar or twig blight. The disease has been
found in 68 species of plants in 40 genera.
Surveys: Phytophthora on Woody Ornamentals
Phytophthora species
found in Minnesota
Nurseries
P. cactorum
P. cambivora
P. citricola
P. citrophthora
P. fragariae var. rubi
P. hedraiandra
P. inflata
P. nicotianae
P. alni
Unknown species
Phytophthora Species Found in:
Potting Media
Irrigation Water
