adria bordas on diseases in the garden
TRANSCRIPT
Diseases in the Garden
Adria BordasFairfax County
Virgi nia Cooperative Extension
Techniques in Good DiseaseDiagnosisCl Use your eyes.Cl Use a good hand lens.Cl Look around: close up and far
awayCl Notice if it is only one plant
family with problem or wholearea
Cl Dig to look at the roots.Cl Use a knife to look under bark.
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Non-living Factors
o Nutrient deficiencyo Water stress (too much or too little)o Temperature stresso Herbicide Damageo Prir Pollution/Ozone
Conditions Necessary forPlant Disease
Pathogen Susceptible host
t Time
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Favorableenvironmental conditions
'0 All three must come together for plantdisease to occur
Living Pathogens:
o Fungi - 8,000o Bacteria - 200-300o Virus - 500+o Nematodes - 500o Insects-- Thousands
Look at the pattern of symptoms for clues ...
[J Random distribution of symptoms more likely to be causedby ..• a living organism (biotia:ause)
[J Non-random distribution of symptoms more likely to becaused by:..• a nonliving factor (abiotic cause)
Look at the patte~of symptoms at differentlevels ...
a Plant parta Whole planta Whole planting
Look for signs of living organisms ...a Fungi
--Fruitin bodies--Mycelium
RustsApril-rest of Season
a Rust Fungi: cedar applerust galls are swelling atthis time
a Two hosts required byfungi to complete lifecycle
a- Mo~t common on apple,crabapple, and hawthorn
a Spores wind blowna Plant resistant varieties
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Timing of symptom development can alsoprovide clues ...a Gradual onset/spread of symptoms usually
indicates ...• a biotic cause
a Sudden onset of symptoms usually indicates ...• an abiotic cause
Remember that decay organisms can foolyou ...
Discula Anthracnose
D Attacks bracts, leaves, stemsa Lethal to treea Progresses from lower
branches upa Favored by cool, wet weathera Problem in shaded, fog-prone
areas
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Control of Discula Anthracnose
[] Plant in full sun, water welln Fungicides:
• Banner Maxx (propiconazole)• DaconilWeather Stik
(chlorothalonf]• Dithane (mancozeb)
[] Resistance• C. florida 'Appalachian Spring'• C. kousa• C. kousa X C. florida hybrids
(Stellar series)
Powdery Mildew of Dogwood
[] Dogwood powdery mildew lessconspicuous than other powderymildews
[] More damaging than other powderymildews• Reduction in root mass• Stunting of tree
[] Fungicides:• Immunox, Systhane(myclobutanil)• Fertilome Systemic Fungicide
(propiconazole)• First Step(potassium bicarbonate)
- [] Resistance
-Days are warm and humid,nights are cool-Good air circulation-Systernic fungicidesareeffective
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Anthracnose ControlsD Do not fertilize with
high nitrogenfertilizers.
D Use trickle or soa kerirrigation.
D Prune out infectedbranches.
D Rake and destroyleaves in fall.
Early July-through rest of season
D Powdery Mildews-600+types
D Host range: Variousherbaceous plants, crapemyrtle, dogwood,sycamore, oak, lilac,phlox, grapes
Galls:
D A gall is an unusualgrowth, usually onthe leaves and stemsof various plants.
D They can be causedby insects, mites,bacteria, and fungi.
D Insect galls areformed the insects ormite release growth -regulating chemicalsas they feed anddevelop.
D The chemicals causethe plant to form agall which provides ahome for thedeveloping insect ormite.
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Crown GallI:J Caused by a bacteriaI:J Affects many different
types of plants
I:J Usually on trunk,crown, or roots
I:J Poor growthI:J Avoid wounds
Black Knot Controlv
lJ Infection occurs onwood of the currentseason's growth
I:J Prune out affectedbranches 12 inchesbelow the infection
Bacterial Scorch
[J Affects many tree specieso Transmitted by leafhopperso Xylella fastidiosainhabits xylem and causesa
slow declinec Symptoms appear initially on individual
branches• Marginal necrosis• Chlorotic halo between brown and green tissue
0_ No qhemical controlsc Oiseasei$ enhancedby drought.
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Seiridium Canker of Leyland Cypress
o Drought predisposes treesto infection
c Elongate cankers form onbranches or trunk
c Cankers bleed resinc Dieback may begin at top
or bottom of treec No Chemicalsc Need proper
watering
Leaf spots and leaf drop
Cl Leaf spots and leafdrop during the laterpart of season
Cl Not a huge concernCl Clean up the leaves,
often, no need forchemical
Cl Make note for nextyear.
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Cherries - Leaf Spots /Leaf Drop
[J Leaf spots/Shot Hole[J Brought on by rains
in April and June[J Fungicide sprays as
a preventative[J Not much you can
do in Aug.[J YES! It can weaken
the tree
Root Rots Cont...a Roots often discoloreda Use plant lab to
diagnose problema Treatment difficult -
soil drenchesexpensive
a Prevent with properplant selection andplanting
Septaria Leaf Spot5eptoria fycopersici
[J Black specks in the centers 0the spots
[J De~oliation is severe w/penods of prolonged warm,wet weather
[J Management requires acombination controls
[J Can survive in soil for 3 years
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~. Phytophthora and other Root Rotsa Plants that are in
water-logged soils dueto over-watering orheavy rains arepredisposed toinfection
a Moisture allows motilespores to move in thesoil
a Pathogen has a widehost range
TomatoDiseases
Most CommonOnes
Early blight-Alternart'a solani
a Can infect plants at anystage during the growingseason
a Progresses rapidly afterplants have set fruit-bottomleaves affected first thenmoves to upper leaves
a Can survive in soils for 1year
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Late Blight:Pi?ytophthora infestans
D Devastate tomatoplantings
D Common in periods ofcool, rainy weather
D water-soaked areasthat enlarge rapidly
D Gives the plant a frostdamaged appearance
Veggie Disease Prevz ntiono Good air circulationo Prune off disease and
chlorotic leaves .o Water at the base of
the plant/no overheadsprinklers
n Increase organicmatter to improvedrainage
o Maintain good soilfertilization andirrigation
o 3 year rotation
Weekly Pest Updates-Univ. Maryland
CI http://ipmnet.umd.edu
Verticillium WiltD Soil borne fungusD Can survive in the
soil for many yearsD Lower leaves yellow
and wiltD Entire plant shrivels
up and diesD V-shaped lesion on
the leaves
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Pest Management
D Records or history of theplant, so you will knowwhat diseases to expect.
D Know the diseasescommon in your area.
D Watch the weather.D Monitor pestsD Good sanitation
Adria Bordas
VirginiaCooperative Extension
Extension AgentHorticulture
Fairfax County(703)[email protected]
!lIJVirginiaTechInvent the Fvturo
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