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IN INTRODUCTION TO PLANTIN INTRODUCTION TO PLANTDISEASES, PART II-FUNGI & BACTERIABACTERIA
FUNGIFUNGI
Fungi are composedFungi are composed of living filaments called hyphae
Need an outside food source
Pathogens of plants and animals, sometimes
300,000 species of f i d ib dfungi described; most are not plant pathogens
THE HUMONGOUS FUNGUSARMILLARIA GALLICAARMILLARIA GALLICA
In 1992, ,Armillaria gallica, a fungus found near Crystal Falls, MI covered 37MI covered 37 acres, was estimated to weigh 10 tons and age was estimated at 1,500 yrs old. You may have seenmay have seen this graphic on Uhaul trucks. Since then larger, older Armillariaspp. have been noted in CO and OR.
FUNGI THE GREATDECOMPOSERS
Fungi recycleFungi recycle nutrients by breaking down dead plant material. Fungi that live on dead plant material are calledare called saprophytes.
MEET THE TROPH FAMILYMEET THE TROPH FAMILY
Autotrophs
Biotrophs
Necrotrophs
AUTOTROPHSAUTOTROPHS
S th i th i t iti l d Synthesize their own nutritional needs (photosynthesis)
Example: Green Plants
BIOTROPHSBIOTROPHS
A i th t l li d An organism that can only live and reproduce on another living organism
Example: powdery mildews, downy mildews, rust fungi
Biotrophs areBiotrophs are also called obligate parasites.
NECROTROPHS A parasite that kills and obtains its A parasite that kills and obtains its
nutrition from dead host cells
Example: Sclerotium rolfsii causesrolfsii, causes southern blight/southern stem rot. Thisstem rot. This fungus survives by producing spherical presting structures called sclerotia.
EXAMPLES OF FUNGALDDISEASES
Mildews (Powdery and Downy)
Rusts and smuts
Vascular wilt diseases Vascular wilt diseases
Root and stem rots
Leaf spots and blights
POWDERY MILDEWS
E il Easily identified by white Powdery mildew mycelium
Resistant
ycan be managed with fungicides. Sprays can be initiated after species and
cultivars are available for
initiated after signs of disease are visible, but don’t wait too
lilac, dogwood, crape myrtle, phlox
late.
phlox, crabapple
Powdery mildew on English oak.
DOWNY MILDEW ONIIMPATIENS
Downy mildew of impatiens has damaged landscape plantings in the U.S. in 2011 andU.S. in 2011 and 2012.
BOXWOOD BLIGHT OFBBOXWOOD
Defoliation of boxwood in one season due to b d bli htboxwood blight (Cylindrocladium buxicola). Boxwood blight gwas first discovered in the U.S. in NC and CT in Oct 2011in Oct 2011.
Photos courtesy of M. Inman, CT Ag Exp Station
RUSTSRUSTS
C d l t Yellow leaf spots and
rust colored pustules
Cedar apple rust is a heteroeciousrust, requiring two unrelated
Numerous hosts including conifers,
hosts to complete its lifecycle. Autoecious rusts
broadleaf plants
May also cause galls,
Autoecious rusts only require one host to complete their lifecycle. y g ,
twig dieback
APPLE SCAB
Found on apple and crabapple
Causes premature leaf drop
Symptoms may be found on leaves and fruit
Also found on pyracantha
ANTHRACNOSE DISEASES
Fungal leaf spot, twig blight and/or
k dicanker disease
Favored by cool, wet weather
Hosts: ash, ,dogwood, maple, oak, sycamore
FUNGAL CANKER DISEASEFUNGAL CANKER DISEASE
Localized infection, often causing b h di b kbranch dieback
May follow drought stress
Prune out dead branches to stop spread
1 YEAR LATER- CANKER HASSMOVED TO MAIN STEM
To prevent: irrigate to i i i tminimize water
stress
Prune out dead branches when ththey are observed or you could lose thecould lose the whole plant
ROOT ROT DISEASES
Affected plants may be stunted, wiltedwilted
Discolored, decayed rootsdecayed roots
Poor drainage, standing waterstanding water, excessive irrigation, favor
Ph t hth t t/j idisease development
Phytophthora root rot/juniper
BLACK ROOT ROT – FOLIARSSYMPTOMS
Black root rot is caused by the fungus Thielaviopsis. BRR causes a slow, progressiveprogressive decline. Initial symptoms are yellow foliage; roots of infected plants are discolored and decayed.decayed.
ROOT SYMPTOMS OF BLACKROOT ROT
Dark, discolored roots on Japanese and bl h ll dblue holly, and inkberry are almost always a symptom of y pblack root rot. Herbaceous hosts include: pansy vincapansy, vinca, petunia
BACTERIABACTERIA
Single celled organisms muchorganisms much smaller than fungal spores
Not visible to the naked eye
Shaped like rods, spheres, helical
BACTERIAL DISEASESBACTERIAL DISEASES
Soft rots
Vascular wilts
Leaf and fruit spots Leaf and fruit spots
Crown gall
Fire blight
Citrus canker Citrus Greening Citrus canker, Citrus Greening
BACTERIAL LEAF SPOTBACTERIAL LEAF SPOT
Xanthomonasleaf spot on English ivyEnglish ivy.
BACTERIA STREAMING FROMPLANT TISSUE
Bacteria streaming from a portion of a bb l fcabbage leaf
infected with black rot. Photo courtesy P. yBachi, Univ of KY.
CROWN GALL
Tumors/galls on stems/rootsstems/roots
Soft, spongy to wooden
Crown gall on a wisteria to wooden
and corky with maturity
a wisteria stem
Bacteria enter through wounds
FIRE BLIGHTFIRE BLIGHT
A bacterial disease of apple, crabapple andcrabapple and pear. Symptoms at right include a classic symptom for fire blight, a “shepherd’s crook” and acrook and a stem canker.
BACTERIAL LEAF SCORCHBACTERIAL LEAF SCORCH
Leaf hoppers are the insect vectors of bacterial leaf scorch Thescorch. The xylem inhabiting bacterium that is the causal agent plugs those vessels that transport water to leavesto leaves resulting in leaf scorch.
Bacterial , vascular wilt disease of shade trees, especially pin oak