handout-ken eastwell-impact of viruses on cherry...
TRANSCRIPT
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Impact of Viruses on Cherry Fruit Size
Dan VillamorKen Eastwell
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�Physiological / Horticultural
�Winter damage to vascular system
�Mineral imbalance (Zn+2 deficiency)
�Pathogens
�Root or crown rots
�Virus-like agents**
Damage to vascular tissue contributes to small fruit:
Many of the VLA’s that lead to small fruit are found in the PNW
Cherry necrotic rusty mottle
Cherry rusty mottle
Cherry raspleaf
Cherry mottle leaf
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�Little cherry virus 1 (LChV1)
�Little cherry virus 2 (LChV2)
�Western X disease phytoplasma (WX)
Pathogens Number of positives per county Total(145)Chelan Yakima Grant Benton
LChV1 0 0 0 0 0
LChV2 38 23 0 10 71
WX 29 6 15 1 51
LChV1/LChV2 1 7 0 0 8
LChV1/WX 4 0 0 0 4
LChV2/WX 6 1 0 2 9
LChV1/LChV2/WX 2 0 0 0 2
(Beers, Villamor, Bixby-Brosi, Eastwell: funded by WTFRC)
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Little cherry virus 2:
� Family Closteroviridae
� Genus Ampelovirus
Little cherry virus 1:
� Family Closteroviridae
� Genus unassigned
Thread-like particles
Symptoms of Little cherry virus 2 :
�LChV2 infected fruit is small, late ripening and insipid
0
2
4
6
8
10
12
Yellow(-22 days)
Pink(-10 days)
Ripe(Harvest)
Fru
it w
eig
ht
(gm
)
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Symptoms:
‘Sweetheart’‘Lambert’
‘Canindex 1’ ‘Bing’
Premature autumn coloration is unreliable
in most cherry cultivars in most years
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(courtesy Landon Michaelson)
Three major factors:
1. Series of cool springs
2. Elevated insect vector populations
3. Heightened awareness of fruit size
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Little cherry virus 2 transmission:
�Apple mealybug:
�Reported in Wenatchee in 1997 (R. Miller)
�Grape mealybug:
�Populations increasing from Southwest
�Infestations becoming more prevalent because of shift to different chemistries.�No spray programs until 2012
�Not an economical pest in absence of virus
Mealybugs are difficult to manage:
� Crawlers dispersed long distances:� in wind� on debris� on farm equipment
�Overwinter in crevices, under bark
�Tree tops�Quickly out of
control
(E. Beers)
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Little cherry virus 1:
�Occurs in Washington State and British
Columbia
�Relatively low incidence throughout state
�Vector(s) unknown for Little cherry virus 1�Spreads more slowly than Little cherry virus 2
�Symptoms:
�Milder than those of Little cherry virus 2
�Together, symptoms are very severe
“Albino”
� Symptoms spread slowly through tree
� Reduced extension
� Fruit severely impacted� Bitter taste
Western X phytoplasma
• Specialized bacteria with no cell wall
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Western X disease
� X-disease of peaches prevalent mostly “in close proximity to virgin, sagebrush land.” (Coe 1942)
�First diagnosed in cherry in Washington in 1946
Western X phytoplasmatransmission:
�Mountain leafhopper (Colladonus montanus)� Overwinters on winter
annual weeds near water (clovers, dandelions, curly dock)
� Adults migrate to orchard weeds in late spring
� Most abundant in sweet cherry (only) but not preferred host and does not colonize
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Western X phytoplasma transmission:�Cherry leafhopper (Fieberiella florii)
�Feed on wide range of woody plants (sweet
cherry, bitter cherry, & choke cherry)
�Most important species for tree-to-tree spread
Cherry leafhopperCherry leafhopperCherry leafhopperCherry leafhopper
Management of Little cherry virus 2:
�Plant only virus-free trees (pollinators!!)
�Prompt removal and replanting
�Rogue symptomatic trees and replace
�Be wary of root grafting
�Remove entire orchard and replant
�Bitter cherry (Prunus emarginata) is a host
�Choke cherry (Prunus virginiana) is NOT a host
�Vector control
�Caution during tree removal
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Western X management:
�Remove diseased trees
�Most important source
�Treat with insecticide before removal
�Manage nearby ornamental hosts
�Includes chokecherry and bitter cherry
�Remove or treat with insecticide
�Control weeds that harbor leafhoppers and phytoplasma
�Treat orchard for leaf hopper vectors
�Delayed dormant oil sprays plus insect control until leaf drop
The correct control strategyis essential for success!!
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For more information:http://healthyplants.wsu.edu