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