bacterial diseases of stone fruit: spots and cankers · 2017-08-01 · bacterial diseases of stone...
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BACTERIAL DISEASES OF STONE FRUIT: SPOTS AND CANKERS
December 16, 2015Kari Peter, Ph.D.Department of Plant Pathology and Environmental MicrobiologyPenn State University Fruit Research and Extension CenterBiglerville, [email protected] 717-677-6116 Ext. 223 @drtreefruit
Overview
– Predisposing factors
– Disease Cycle– Symptoms– Management
Bacterial cankerPseudomonas syringae pv. syringaePseudomonas syringae pv. morsprunorum
Bacterial spotXanthomonas arboricola pv. pruni(Xap)
G. Sundin, MSU
S. Bardsley, PSU
Bacterial Spot• Predisposing factors favoring the occurrence
of bacterial spot Cultivar susceptibility
Early bud break and early fruit ripening
Sandy soils (ring nematode) Very clay soils (drainage)
~ 86 °F temperature
Relative humidity of 100% over a period of 3 days = appearance of disease
http://www.ent.uga.edu/peach/peachhbk/pdf/stages.pdf
Forestryimages.org
Bacterial Spot Disease CycleSpring
SummerFall/Winter
Polycyclic diseaseOptimum conditions:Warm and wetDisease slows down:Hot and dry
Overwinter in cankers, infected buds, leaf scars
First infect leaves
Infect leaves and fruit
Left untreated: bacterial
populations “explode”
Bacterial Spot Symptoms - Twigs
• Cankers• Bark cracking• Black Tip
• Lack of vegetative growth• Overwintering site for bacteria
D. Ritchie, NCSU
K. Peter, PSU
Bacterial Spot Symptoms - Leaves
Bacterial Spot
Copper/Chemical Injury
• Round (like a water droplet)
• Follows spray pattern
• “Swiss cheese”
• Yellowing not always associated with lesions
• Defoliation of older leaves
• Captan and sulfur injury: similar symptoms
• Angular• Always
bordered by the veins
• Few or many lesions
• Yellowing associated with lesions
Defoliation– it does not take many lesions for this to occur
K. Peter, PSU
K. Peter, PSU
See spots? Ask yourself:• Are the spots angular?• Are the spots defined
by the small leaf veins?
Bacterial Spot Symptoms - Leaves
K. Peter, PSU
Early symptoms –light green water-soaked lesions
See spots? Ask yourself:• Are the spots angular?• Are the spots defined
by the small leaf veins?
Bacterial Spot Symptoms - Leaves
K. Peter, PSU
Bacterial Spot Symptoms - Fruit• Early Season Lesions
– 3 weeks after petal fall– Irregularly shaped– Pits extend deep into fruit
• Late Season Lesions– Shallow pits – Skin Cracking– Secondary infection: brown rot
Early season
After pit-hardening
Bill Shane, MSU
K. Peter, PSU
S. Bardsley, PSU
S. Bardsley, PSU
Japanese plum
Bacterial Spot Symptoms - FruitNot to be confused with Peach Scab
– Circular lesions– Dark olive-brown, fuzzy lesions
– Lesions form pattern– No fruit surface pitting– No foliar symptoms
BACTERIAL SPOT PEACH SCAB
S. Bardsley, PSU Bugwood.org
Bacterial Spot ManagementMain Strategies
– Prune out cankers– Resistant Cultivars
• Not immune = Still need control measures
– Chemical Control• Copper• Oxytetracycline• Biological products• Product rotation
http://njaes.rutgers.edu/peach/
Bacterial Spot ManagementCopper– Fixed vs. Bluestone– Dormant spray– Cover sprays using fixed copper
• Clean fruit vs. Leaf phytotoxicity• Defoliation: older leaves
– Avoid using copper during slow drying conditions: worsens leaf phytotoxicity
– Do not mix copper with phosphorous acid products (Rampart, ProPhyt, etc.) or foliar fertilizers
K. Peter, PSU
Bacterial Spot Management: Copper recommendations (N. Lalancette, Rutgers)
Recommended rate based on the metallic copper concentration of 0.5% = 1XCan increase concentration to 2X (1%multiply current recommended rate times 2)
** Be sure to monitor shoot s for increase in defoliation when using 2X rate**
Bacterial Spot Management
Oxytetracylcine (Mycoshield, FireLine)– Suppresses bacteria– 48 hr control window (UV degradation) – Risk of resistance– Persistent yield loss– Best when used in rotation with other products– Label limitations
Bacterial Spot ManagementA plan…
– Start applications late petal fall to early shuck split– Spray 7 – 14 days according to conditions– Rotating other products with oxytetracycline (21
day PHI) and copper (PHI varies)• Serenade Optimum (14 oz/A) or Double Nickel (1 qt/A)
– Works well in rotation– Can be tank mixed with oxytet
– For apricots, plums, etc: Cueva, Badge, Kocide, etc; Serenade Optimum, Double Nickel
– ** Always double check the label**– Phosphorous acid products ineffective
If your crop was frozen out: you still need to control for bacterial spot!
• If you don’t control the disease in no-crop years:• Build up of inoculum—issues for subsequent
years• Stress – defoliation; weakens tree making it
more susceptible to bacterial spot in coming years
Bacterial Spot Management
Overview
– Predisposing factors
– Disease Cycle– Symptoms– Management
Bacterial cankerPseudomonas syringae pv. syringaePseudomonas syringae pv. morsprunorum
Bacterial spotXanthomonas arboricola pv. pruni(Xap)
G. Sundin, MSU
S. Bardsley, PSU
Bacterial Canker
Perpendicular VVertical AxisMarchantVogel SlenderSpindleModified Central Leader Spanish Bush
Ranked in order of increasing vulnerability to canker infections Training systems
• Predisposing factors favoring the occurrence of bacterial canker
Least susceptible
Most susceptible
Source: http://nysipm.cornell.edu/grantspgm/projects/proj09/fruit/carroll5.pdf
Bacterial Canker• Predisposing factors favoring the occurrence of
bacterial canker
Cultivar susceptibility – varies by cultivar• Sweet cherry, sour cherry, plums, prunes,
peaches
Rootstock susceptibility• Gisela rootstocks highly susceptible• Mazzard more resistant
Bacterial Canker• Predisposing factors favoring the occurrence of
bacterial canker Acidic soils Sandy and clay soils Nutrient deficiency High ring nematode populations
Winter pruning Spring freezes Bacteria: Ice nucleation proteins & frost injury
• Proteins allow water to freeze at higher temperatures resulting injury to the plant
• Bacteria “feed” on the nutrients released by the injured plant tissue
Bacterial CankerFavorable conditions - susceptibility
• Mid-April (cool, wet, frost injury):– Bacteria overwintering in buds, cankers– P. syringae populations increase 10 – to 100 – fold during
bloom (blossom infection – blossom blast)• Summer:
– Humid, wet weather: symptoms on leaves and fruit– Hot and dry conditions: P. syringae populations low
• Autumn rains and cooler temperatures:– P. syringae detected at high levels prior to and during leaf fall
• *** Infection at leaf scars can be high• Early to mid-winter
– Bacteria overwinter in cankers, dead buds, healthy buds– Exposed to severe temperatures increases chance of infection
**Wind and rainstorms move the bacteria
Bacterial Canker Symptoms
Blossom – Blossom Blast
G. Sundin, MSU
• Not to be confused with blossom blight caused by the fungus causing brown rot
• No sporulation(differentiates from brown rot)
Bacterial Canker SymptomsFruit
• Sporadic• Water – soaked lesions• Chocolate – brown lesions
Leaves• Sporadic• Necrotic lesions, chlorotic rings• “Shot hole” appearance• Lesions occur along leaf margin
– curling effect
www.omafra.gov.on.ca
K. Peter, PSU
W. Turechek, USDA-ARS
Bacterial Canker SymptomsBranches and Trunk
• Facilitated by stress– Spring frost– Severe winter freezes– Water – soaking– Blossom infection– Pruning wounds– Insect injuries
• Sunken bark• Amber gummosis• Girdled branches and
trunks• Limb or tree death
• No alternating callus rings
http://commons.wikimedia.org/wiki/File:Bacterial_Canker_-_Gummosis_on_Cherry.JPG http://commons.wikimedia.org/wiki/File:Bacterial_Canker_on_Cherry.JPG
Bacterial Canker Management• Goal: reduce number of bacteria before trees
enter susceptible period
• Using Copper*– Copper alone: evidence shows limited ability to
control– Bordeaux mixture PLUS vegetable oil
• Win Cowgill – Rutgers• Described:
http://jerseyfruitagupdates.blogspot.com/2012/09/spray-cherries-for-bacterial-canker.html
– Sept, Oct, Nov, and in spring– EXAMPLE:Timing Copper sulfate Lime Water Veg. OilSept 4 lb 6 lb 100 gal 2.8 qtOct - early 5 lb 7 lb 100 gal 2.8 qtOct – late 8 lb 10 lb 100 gal 2.8 qtNov 10 lb 10 lb 100 gal 2.8 qtSpring 5 lb 7 lb 100 gal 2.8 qt
Notes: Use Powdered copper sulfate (bluestone or blue vitriol); Use FRESH hydrated lime (good quality calcium hydroxide)
Tank ½ full of water + agitation: Add copper, then lime, then the oil
K. Peter, PSU
Bacterial Canker Management
• Pruning* – Avoid large dormant cuts– Minimize impact of disease
with summer pruning– 12 inch rule: distances infection
from the main trunk– “Ugly stub”
www.extension.umd.edu
Bacterial Canker Management• Avoid tree training methods that cause
injury (limb spreaders)• Remove/Prevent tree stressors
– Plant in well drained soils– Maintain adequate nutrients– Weed control: weeds support
populations of bacteria– Control nematodes– Remove wild Prunus– Do not interplant new trees with old
trees• Old trees source of bacteria
K. Peter, PSU
Take home messages:
Bacterial spotResistant cultivarsWarm, humid temps favor high bacterial populationsDormant copper sprays; reduced rates during the seasonFavorable conditions throughout the season: Use a rotation of
products (copper, oxytetracycline, biologicals)Still need to control with or without crop
Bacterial cankerSusceptibility of rootstocks and cultivarsSpring freezes, cool fall weather promote diseaseMindful pruning – summer (low bacteria numbers)Limited control options (Bordeaux mixture in fall and early
spring)
Maintain healthy trees!
QUESTIONS?Kari Peter, [email protected] @drtreefruit
BACTERIAL DISEASES OF STONE FRUIT: SPOTS AND CANKERS