Evaluation of Actigard for Control of Iris Yellow Spot Virus in Onion Bulb Crops

Lindsey du Toit & Mike Derie Washington State University Mount Vernon NWREC

Evaluation of Actigard, as discussed in this presentation, was done using an experimental use permit granted by WSU/WSDA. Application of a pesticide to a crop or site that is not on the label is a violation of pesticide law and may subject the applicator to civil penalties up to $7,500. In addition, such an application may also result in illegal residues that could subject the crop to seizure or embargo action by WSDA and/or the U.S. Food and Drug Administration. It is your responsibility to check the label before using the product to ensure lawful use and obtain all necessary permits in advance.

Iris yellow spot • Iris yellow spot tospovirus (IYSV) • Host range: - iris, lisianthus, Eustoma, … - Alllium spp. - ‘experimental’ hosts (e.g., Nicotiana benthamiana) - possible weed hosts (redroot pigweed, kochia, …) • Onion thrips vector (Thrips tabaci) • Strains of IYSV IYSV on iris in the Netherlands

Symptoms of IYSV: Onion bulb crops

Photo courtesy of M. Trent

Talon

Redwing

Symptoms of IYSV: Onion seed crops

Dissemination and survival of IYSV: Host • Volunteers • Transplants • Viruliferous thrips on bulbs • “Green bridge” effect • NOT seedborne

Impact of IYSV: Onion bulb crops

(du Toit & Pelter, 2005. Biological & Cultural Tests 20:V006)

Bulb yield (tons/acre) = 33.45 + Bo(cultivar) – 0.11 X1 – 0.14 X2 – 0.12 X3 Bo ranged from -5.83 (for ‘Copra’) to +33.03 (for ‘Ranchero’) (R2 = 0.88, CV=12.1)

% Colossal + jumbo bulbs = 16.38 + B0(cultivar) – 0.15 X1 – 0.17 X2 – 0.18 X3 Bo ranged from -1.34 (for ‘OLYH 02N2’) to +37.69 (for ‘PX 2599’) (R2 = 0.83, CV=34.4)

Impact of IYSV: Onion seed crops 1.40

Seed yield (g/umbel)

1.20 1.00 0.80 0.60 0.40 0.20

1.2716 X 10% increase in IYS Yy ==-0.0081x 1.272 –+ 0.008 2 2 = RR = 0.7486 = 6% loss in seed yield 0.75

0.00 0.00

20.00

40.00

60.00

80.00

Incidence of plants with IYSV (%)

100.00

Actigard Acibenzolar-S-methyl (Syngenta Crop Protection) - induces systemic resistance in plants to diseases, insects, nematodes, … - does NOT kill pathogens or pests - effective at very low doses (0.25-1.00 oz/acre) - expensive (~$100/oz) - 4 applications/season, 7-10 day spray interval - phytotoxic at higher rates & no. of applications

Actigard Acibenzolar-S-methyl (Syngenta Crop Protection) - induces systemic resistance in plants to diseases, insects, nematodes, … - does NOT kill pathogens or pests - effective at very low doses (0.25-1.00 oz/acre) - expensive (~$100/oz) - 4 applications/season, 7-10 day spray interval - phytotoxic at higher rates & no. of applications - Actigard for control of IYS in onions?

- bulb crop trials by Schwartz, Colorado State Univ. - reduced losses to IYS & Xanthomonas leaf blight - CO Section 18 emergency registration - WA seed & bulb crop trials by du Toit, WSU

Disease Suppression by Actigard and Imidacloprid 45

(Howard Schwartz, Colorado State University)

D isease Incidence (# infected plants)

40 35 30

Untreated Actigard Admire

25 20 15 10 5 0 10-Jul-03

17-Jul-03

24-Jul-03 Date

31-Jul-03

Yield of Actigard and Imidacloprid Treated Onions, Fagerberg Farm 2003 (Howard Schwartz, Colorado State University)

Yield (cw t/A )

600 500

Untreated

400

Admire

a

Actigard

300 200

a b

b

a

a bc c

100 0 Medium

Jumbo Yield Component

Total

a

2005-2006 Actigard Studies

Howard Schwartz, Colorado State University

------------------------------------------------------------------Control = 27% IYSV 56% IYSV Actigard @ 0.76 oz x 4 apps = 16% 62% [4, 3, 2 & 1 week pre-bulb initiation] ------------------------------------------------------------------Control = 47% IYSV Provado @ 3.75 oz x 4 apps = 29% Warrior @ 3.84 oz x 4 apps = 25% [addition of Actigard did not reduce incidence of IYS] ------------------------------------------------------------------No phytotoxicity when tank-mixed with other pesticides ------------------------------------------------------------------Control = 74% IYSV 19% Xanthom. Actigard @ 0.76 oz x 4 apps = 54% 4% [4, 3, 2 & 1 week pre-bulb initiation] -------------------------------------------------------------------

IYSV onion seed crop trial in WA 2004-05 = RCB design, 5 reps, 3 x 4 factorial (60 plots) • Neonicotinyl insecticide seed treatments: - Cruiser (thiamethoxam, Syngenta) - Poncho (clothianidin, Bayer) - Control • Foliar applications of Actigard (acibenzolar-S-methyl, Syngenta) + Provado (imidacloprid, Bayer): - Fall only (early + late Sep.) - Spring only (4x @ 3-wk intervals starting late Mar.) - Fall + spring - None (control) • Entire trial duplicated without Provado in foliar applications • Assessments: - Plants sampled & assayed for IYSV (3x, Pappu’s lab) - Symptoms rated (incidence & severity in July ‘05) - Seed yield & germination measured

Results: No significant effects on IYS or seed yield

IYSV onion seed crop trials in WA: 2005-06 Seed or drench treatments

ELISA assays (%)

IYSV symptoms (Jul 2006)

Oct 2005#

Jul 2006*

Severity (0-4)

Incidence (%)

Lodged (%)

Seed yield (g/5’ row)

Control

13.0 a

7.3 a

0.83 a

47.4 a

4.65 a

35.9 a

Cruiser

13.3 a

7.3 a

0.75 a

47.6 a

2.88 a

31.3 a

Poncho

11.3 a

9.3 a

0.89 a

50.0 a

4.92 a

23.7 b?

Platinum

10.3 a

10.0 a

0.75 a

45.7 a

4.19 a

20.8 b?

Foliar Actigard treatments Control

11.0 a

11.0 a

0.71 a

41.0 a

3.80 a

21.2

Fall only

16.5 a

11.0 a

0.87 a

50.5 a

4.27 a

25.0 bc

Spring only

16.0 a

10.0 a

0.80 a

46.8 a

4.45 a

17.1

d

Fall + spring

9.0 a

4.0 a

0.84 a

47.6 a

4.68 a

17.4

cd

Act. + Provado

9.5 a

8.0 a

0.88 a

53.3 a

4.51 a

27.9 b

Act. + Success

10.0 a

7.0 a

0.74 a

46.7 a

3.26 a

59.1 a

Oct 2005 = % of 10 seedlings sampled randomly/plot that tested positive for IYSV by ELISA * Jul 2006 = % of 5 asymptomatic plants positive by ELISA + % symptomatic plants

#

cd

2007 WA Onion Bulb Crop Actigard Trial

1. Rates of Actigard: 0.25 to 1.00 oz/acre 2. Timing of application relative to bulb initiation (~20 June): 6 weeks prior (9 May), to 1 wk after (28 June) 3. Number of applications: 0, 2, 4, or 8 • Randomized complete block design, 4 replications • Drip-irrigated crop of cv. Talon, planted 4 April

2007 WA Onion Bulb Crop Actigard Trial Actigard treatments Treatment no.

Number of weeks pre-bulb initiation 6

5

4

3

2

1

0

+1

5/09

5/16

5/23

5/30

6/08

6/14

6/20

6/28

1

0

0

0

0

0

0

0

0

2

0.75

0.75

0.75

0.75

3

0.75

0.75

0.75

0.75

4

0.75

5

0.75

6

1.00

0.75

0.75 1.00

7

0.75

8

0.75

9

0.25

0.25

0.25

0.25

0.25

1.00 0.75

0.75

0.75 0.75

0.25

0.25

0.25

• R-11 surfactant (2.0 pt/100 gal) used for all applications, including control plots • Applied with a CO2-pressurized backpack sprayer (33 gpa), on 25’ of 2 center beds/plot

2007 WA Onion Bulb Crop Actigard Trial 20 June 2007

• Thrips counted on 10+ plants every 2 weeks • IYS symptoms 1st observed in late June • Incidence & severity of IYS rated for 5’ of 1 bed/plot on 18 July, & 3 & 15 August • Bulbs topped, sized, & weighed by size for 5’ of center 2 beds/plot on 26 September

2007 WA Onion Bulb Crop Actigard Trial Severity of IYS (0 to 6)

1 5

2

3

4

6

2007 WA Onion Bulb Crop Actigard Trial

2007 WA Onion Bulb Crop Actigard Trial Mean severity of IYS 6

No significant differences among treatments at any date

Severity of IYS

5 4

*

*

3 2 1

C 0. 75 on tr oz o :6 l ,5 ,4 0. ,3 75 oz 0. 75 :6 ,3 oz :4 ,3 ,2 0. ,1 75 oz :4 ,1 1 oz 0. 75 :4 ,2 oz : 2 ,0 ,1 ,0 0. ,+ 75 1 o 0. 25 z: 2 ,+ oz :6 1 to +1

0

18-Jul 3-Aug 15-Aug

2007 WA Onion Bulb Crop Actigard Trial Mean incidence (%) of plants with IYS 90 80

*

*

70

No significant differences among treatments at any date

60 50 40 30 20 10 0 C 0. on 75 oz tro :6 l ,5 ,4 0. ,3 75 0. oz 75 :6 oz ,3 :4 ,3 ,2 0. ,1 75 oz :4 ,1 1 oz 0. :4 75 ,2 oz ,0 :2 ,1 0. ,.. 75 . oz 0. :2 25 ,+ oz 1 :6 to +1

Incidence (%) of IYS

100

18-Jul 3-Aug 15-Aug

C on tr

ol oz :6 ,5 ,4 ,3 0. 75 oz 0. :6 75 ,3 oz :4 ,3 ,2 ,1 0. 75 oz :4 ,1 1 oz :4 0. ,2 75 ,0 oz :2 ,1 ,.. 0. . 75 oz :2 0. 25 ,+ 1 oz :6 to +1

0. 75

Total marketable yield (tons/acre)

2007 WA Onion Bulb Crop Actigard Trial Total marketable yield (tons/acre) 35

No significant differences

30

25

20

15

10

5

0

2007 WA Onion Bulb Crop Actigard Trial Mean bulb yield by size (tons/acre) *

*

No significant significant No differences differences among among treatments treatments

15

10

5

0 C 0. on 75 oz tro :6 l ,5 ,4 0. ,3 75 0. 75 oz: 6, oz :4 3 ,3 ,2 0. ,1 75 oz :4 ,1 1 o 0. z: 75 4 oz ,2,0 :2 ,1 0. ,.. 75 . oz 0. :2 25 ,+ oz :6 1 to +1

Yield (tons/acre)

20

Jumbo + Colossal Medium Pre-pack

2007 WA Onion Bulb Crop Actigard Trial Effect of IYS gradient W

E

3.3 3.2 3.5 3.2 3.3 3.2 3.7 3.6 3.9 3.5 4.1 4.2 3.1 2.7 3.0 3.2 3.2 3.1 3.2 2.9 3.9 3.5 3.9 3.9 2.8 2.8 3.2 2.7 3.1 3.1 3.3 3.7 2.9 3.5 3.8 3.7 • All IYS ratings and yield measurements differed significantly among replications • Replications 1 & 3 (east) = highest disease & lowest yields • Disease gradient confounded ability to differentiate among Actigard treatments

Conclusions & recommendations for use of Actigard to control IYSV • Difficulty: natural thrips & IYS outbreaks = non-uniform disease & vector pressure • Actigard efficacy - potential value for management of IYS - questions: timing, rate(s), phytotoxicity, costs? - bulb vs. seed crops = annual vs. biennial • IYS management = effective thrips management - conventional & “soft” insecticides - select thrips-tolerant or “less attractive” cv’s • Avoid green bridges • Fumigate bulbs &/or transplants? • Cultural practices - irrigation (overhead) - straw mulch, avoid stress & poor stands - avoid excessive nitrogen

• Nitrogen fertility & thrips/IYSV?

- Utah onion grower: - build soil organic matter - minimize nitrogen fertility - 10 gpa 10-34-0 at planting + biological product - 300 lb ammonium sulfate at 2-leaf stage - split rest of N through to late July/early Aug leaf color & soil conductivity (~300 uS) liquid 32 applied in water - Has not had to spray for thrips (in 3 years)!

Acknowledgements Chris Clemens, Syngenta Crop Protection

Columbia Basin Vegetable Seed Assoc. Pacific Northwest Vegetable Assoc. WA State Comm. on Pesticide Registration Seed companies, growers, field reps

Mike Derie,

© Play With Your Food

Alyse Douglass, Cynthia Hansen, Leigh Ann Harrison, Barbara Holmes, Carrie Miller