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Aphid Ecology and Epidemiology of Cucumber Mosaic Virus in Snap Bean Fields:
Implications for Management
Aphid Ecology and Epidemiology of Cucumber Mosaic Virus in Snap Bean Fields:
Implications for Management
Brian A. NaultDepartment of EntomologyCornell UniversityNew York State Agric. Exp. Stn.Geneva, NY
Brian A. NaultDepartment of EntomologyCornell UniversityNew York State Agric. Exp. Stn.Geneva, NY
Updated March 2007Updated March 2007
Snap Bean/ Aphid/ Virus ProjectSnap Bean/ Aphid/ Virus ProjectCornellEntomology - Brian NaultHorticultural Sciences - Alan Taylor, Phillip Griffiths, Steve
ReinersPlant Pathology - Denis Shah, Helene Dillard, Tom Zitter and
Marc FuchsCooperative Extension - Arlie McFaul and Julie Kikkert
Penn StateEntomology - Shelby Fleischer and Amanda BachmannPlant Pathology - Fred GildowCooperative Extension - Tom Butzler
Snap Bean/ Aphid/ Virus ProjectSnap Bean/ Aphid/ Virus Project
IndustryNY and PA Vegetable Industries – growers and processors Seed Companies – Seminis, Harris Moran and SyngentaSeed Health Testing – STA Inc.
CollaboratorsUniversity of Wisconsin - researchersUSDA-ARS - researcher
Snap Bean/ Aphid/ Virus ProjectSnap Bean/ Aphid/ Virus Project
2001 - Catastrophic yield losses due to viruses observed in NY
2002 - Systemic seed treatments (e.g., Gaucho and Cruiser) andfoliar insecticide sprays not effective against viruses;Identified aphids and viruses in fields
2003 - CMV can be seed transmitted, but uncommon;Identified aphids and viruses in fields
2004 - Search for CMV-tolerant cultivars;Identified aphids and CMV incidence in fields;Determined transmission efficiency by aphids
2005 - Perhaps, worst epidemic of CMV ever experienced in NY;Search for CMV-tolerant cultivars;Identified aphids and CMV incidence in fields
Estimated Losses in Processing Snap Beans Attributed to Viruses in New York
Year Loss (US $) 2001 2,000,000 2002 700,000 2003 1,000,000 2004 500,000 2005 1,500,000 2006 0 Total 5,700,000
*Estimate in 2006 from Bird’s Eye Foods, Rochester, NY
‘Goldmine’‘Goldmine’
Yield Reduction Attributed to Viruses
‘Hystyle’ ‘Hystyle’
Quality Reduction Attributed to VirusesQuality Reduction Attributed to Viruses
Viruses Detected in Snap Bean Fields in Midwestern and Northeastern US Since 2000
Viruses Detected in Snap Bean Fields in Midwestern and Northeastern US Since 2000
Cucumber mosaic virus (CMV)Alfalfa mosaic virus (AMV)Bean common mosaic virus (BCMV)Bean yellow mosaic virus (BYMV)Clover yellow vein virus (C1YVV)Watermelon mosaic virus (WMV-2)Clover yellow mosaic virus (C1YMV)Bean pod mottle virus (BPMV)Tomato spotted wilt virus (TSWV)Tobacco streak virus (TSV)
* Viruses highlighted yellow may be transmitted by aphids
Cucumber Mosaic Virus (CMV)Cucumber Mosaic Virus (CMV)
‘Hystyle’‘Hystyle’
Modes of CMV TransmissionModes of CMV Transmission
Seed transmitted
Transmitted by aphids in a non-persistent,stylet-borne1 manner
- Acquired within seconds- Transmitted within seconds- Persists in aphid less than 1 hour- More than one plant can be infected- Non-colonizing aphids common vectors
1 Nault, L. R. (1997). Ann. Entmol. Soc. Am. 90: 521-541.
Soybean aphidSoybean aphid
Key Vector?Key Vector?
Aphis glycines
Soybean
AlfalfaAlfalfa Snap BeansSnap Beans
Major Source of CMVMajor Source of CMV
avg. 13 to 19% of alfalfa plants infectedperennial (4 to 6 year rotation)>230,000 ha of alfalfa (17x more than snaps)grown in proximity of bean fields
avg. 13 to 19% of alfalfa plants infectedperennial (4 to 6 year rotation)>230,000 ha of alfalfa (17x more than snaps)grown in proximity of bean fields
soybean alfalfa
snap bean
NO CMV CMV
Expected Sequence of Events
Soybean aphid
Solutions for Managing CMV or Aphids that Spread CMV
Solutions for Managing CMV or Aphids that Spread CMV
Most effective solutionCultivars resistant to CMV
Ineffective solutionInsecticides (e.g., foliar sprays or seed treatments)
Alternative solutions for some cropsReflective mulches Row coversMineral and stylet oilsCultural practices (e.g., field location, planting dates)
Short-Term Solution for Reducing Risk of Yield Loss by CMV
Short-Term Solution for Reducing Risk of Yield Loss by CMV
Plant CMV-tolerant cultivars ratherthan CMV-susceptible ones duringperiod of greatest risk for a highlevel of CMV infection
Objectives
1) Monitor CMV incidence in snap bean fields
2) Monitor aphid flight activity in snap bean fields and identify most common species
3) Identify commercial snap bean cultivars that are tolerant to CMV
Regions Sampled in New York
Orleans
Genesee Ontario
CMV and Aphid Sampling PeriodsIn Snap Bean in New York
0
10
20
30
40
5/5 5/19 6/2 6/16 6/30 7/14 7/28 8/11 8/25 9/8 9/22 10/6
Date
Middle-Planted
Planting PeriodPlanting Period
Late-Planted
Early-Planted
Monitoring CMV IncidenceMonitoring CMV Incidence2002-2006 in NY
Planting periods:Early (5/15 - 6/15)Middle (6/25 – 7/10)Late (7/20 – 7/31)
n = 4 fields/period
125 plants/ field
Sampled weekly
DAS-ELISA
Monitoring Aphid DispersalMonitoring Aphid Dispersal2002 –2006 in NY
Planting periods:Early (5/15 - 6/15)Middle (6/25 – 7/10)Late (7/20 – 7/31)
n = 4 fields/period
5 traps/field
Sampled weekly
Aphids identified by Dr. Randi Eckel
ceramic tile on bottomceramic tile on bottom
Maximum % Incidence of CMV in Snap Bean Fields in New York
Planting Period 2002 2003 2004 2005 2006
Early 27.3 a 15.6 a - 12.2 a 5.1 a
Middle 54.2 b 4.5 a 1.5 a 100.0 b 3.0 a
Late - - 12.4 b 100.0 b 0.3 a 1 Means within a year followed by the same letter are not significantly different
(P>0.05; Fisher’s Protected LSD; n=4).
Year1
Season Total Number of Aphids per Trap in Snap Bean Fields in New York
Planting Period 2002 2003 2004 2005 2006
Early 10.7 a 15.7 a - 19.9 a 14.9 a
Middle 30.7 b 22.6 b 10.1 a 85.7 b 6.1 a
Late - - 17.1 b 22.3 a 1.7 a
1 Means within a year followed by the same letter are not significantly different(P>0.05; Fisher’s Protected LSD; n=4).
Year1
Highest within Season Total Number of Aphids and % Incidence of CMV
Planting Period 2002 2003 2004 2005 2006
Early 10.7 a 15.7 a - 19.9 a 14.9 a
Middle 30.7 b 22.6 b 10.1 a 85.7 b 6.1 a
Late - - 17.1 b 22.3 a 1.7 a
1 Means within a year followed by the same letter are not significantly different(P>0.05; Fisher’s Protected LSD; n=4).
Year1
Most Common Aphid Species Dispersing in Snap Bean Fields
Yellow clover aphid
Pea aphid
Major host - Alfalfa Major host – Corn or Soybean
Corn leaf aphid
Soybean aphid
Probability of a Single Aphid Successfully Transmitting CMV (Le-Strain) to Snap Bean
Yellow clover aphid
Pea aphid
Alfalfa Corn and SoybeanCorn leaf aphid
Soybean aphid
8.2% 8.6%
5.2% 3.5%
F. Gildow, Penn State Univ., unpublished
Most Common Alate Aphids in Snap Bean Fields in New York
Period 2002 2003 2004 2005
Early
Pea aphid (56%)
Yellow clover aphid (14%)
Pea aphid (23%) Corn leaf aphid (15%)Yellow clover aphid
(11%)
- Pea aphid (33%)
Yellow clover aphid (19%)
Middle
Yellow clover aphid (77%)
Soybean aphid
(64%) Corn leaf aphid
(12%)
Pea aphid (15%)Soybean aphid
(13%) Corn leaf aphid
(35%)
Pea aphid (13%) Soybean aphid
(14%)
Yellow clover aphid (58%)
Late - -
Soybean aphid (10%)
Corn leaf aphid (30%)
Soybean aphid (24%)
Yellow clover aphid
(25%) 1 Percentage of total number of aphids captured within planting period.
Year1
alfalfa
snap bean
CMV
Likely Sequence of Events(mid May – late June)
“early”
Very little aphid migration into beans and very little CMV infection
alfalfa
snap bean
CMV
Likely Sequence of Events(late June – mid July)
“early”
Pea aphid
Pea aphid migrates into beans, but CMV infection occurs between bloom and harvest
soybean
alfalfa
snap bean
NO CMV
CMV
Likely Sequence of Events(mid July through September)
NO CMV
corn snapbean
“early” “late”
Yellow clover aphid
Soybean aphid
Corn leaf aphid
Assigning CMV Risk Periods forSnap Bean Planting in New York
0
10
20
30
40
5/5 5/19 6/2 6/16 6/30 7/14 7/28 8/11 8/25 9/8 9/22 10/6
Planting PeriodPlanting Period
“Late”
“Early”
Date
High RiskLow Risk
Impact of CMV on Snap Bean Yield?Impact of CMV on Snap Bean Yield?
3
A. Taylor, Cornell Univ.
0
20
40
60
80
100
0 1 2 3 4 5
Severity Rating
% R
educ
tion
in Y
ield
Low High
Predicted Relationship Between Foliar Symptom Severity Rating and % Reduction in Yield
0
20
40
60
80
100
0 1 2 3 4 5
Severity Rating
% R
ed
uct
ion
in
Yie
ld
Low High
DandyMasai Summit
Titan
Hystyle
Zeus
Goldrush
Actual Relationship Between Foliar Symptom Severity Rating and % Reduction in Yield
Impact of CMV on Snap Bean Yield Impact of CMV on Snap Bean Yield
Planted cultivars intwo row plots
Covered plants with Reemay Row Cover
Inoculated 1 row withCMV at 1st trifoliate;the other row notinoculated
Harvested, weighed and graded pods
A. Taylor, Cornell Univ.
Response of Cultivars to CMV Infection (large seeded cultivars)
% Yield Reduction Cultivar Source 2004 2005 2006a 2006b
Hystyle HM 31 12 23 0
Sparticus Syngenta - 38 12 9
Summit Syngenta 22 55 38 29
Titan Seminis - 45 23 22
Zeus Seminis 0 0 33 0
a – Planted on 25 Mayb – Planted on July 6
Note: % CMV infection levels were not determined in 2004 or 2005; % CMV infection levels in 2006 were low – only 8 to 52%
ConclusionsConclusionsSoybean aphid is one of four major vectors ofCMV in snap bean fields
Yellow clover aphid, Therioaphis trifolii, is likelythe most important vector of CMV
Only plantings of snap bean during last halfof season (planted after late June) may be at highrisk for yield loss due to CMV
Management should focus on the late plantings; Substitute CMV-tolerant cultivars for susceptibleones