root rots: phytophthora that attack the fine feeder roots...

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

https://www.youtube.com/watch?v=rTo6UwnZiQg

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