predicting tomato spotted wilt virus on tobacco in north carolina a.l. mila dept. of plant pathology
TRANSCRIPT
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Predicting Tomato Spotted Wilt Predicting Tomato Spotted Wilt Virus on tobacco in North Virus on tobacco in North
CarolinaCarolina
A. L. Mila
Dept. of Plant Pathology
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TSWV symptoms on tobacco
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Thrips: the culprit
Frankliniella fusca
TSWV epidemiology on tobacco
• Wide range of hosts
• (>500 spp.,>50 families)
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TSWV incidence in NC
2.12.82.9
3.53.9
1.240.48
6.30.70.71
10.08
0 2 4 6 8
199819992000200120022003200420052006200720082009
Question:
What is next season’s expected TSWV risk
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TSWV in NC (1993-2007)
Severe TSWV epidemics (8 counties)
TSWV epidemic in 2002 and then occasionally (12 counties)
TSWV in “trace” (38 counties)
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What can a grower do?
Imidacloprin (such as, Admire Pro: 0.8 oz/1000 pl)AND Actigard (0.5 oz – 1 oz/50,000 pl drench OR 10 – 25
ppm float water)
Chemical control in the greenhouse
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Untreated control
Actigard 25 ppm [float water]
Actigard: 4 weeks after transplant
Wake co. 2006
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Actigard: 6-7 weeks after transplant
Untreated controlActigard 25 ppm [pretra]
Wake co. 2006
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Question:
Which fields will have > 25% TSWV?
What can a grower do?
• Imidacloprin (such as, Admire Pro: 0.8 oz/1000 pl)
AND (if TSW incidence > 25%) • Actigard (0.5 oz – 1 oz/50,000 pl drench OR 10 –
25 ppm float water)
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Two questions to answer:
• Question - pre-season risk
What is next season’s expected TSWV risk?
• Question - in-season riskWhich fields will have > 25% TSWV?
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TSWV in NC (1993-2007)
Severe TSWV epidemics (8 counties)
TSWV epidemic in 2002 and then occasionally (12 counties)
TSWV in “trace” (38 counties)
A total of 489 cases 58 counties 14 years (1993 – 2007)
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Objectives
• Determine if any weather factors are predictors of TSWV risk at the county level
Time: September before transplant to August (harvest)
Weather factors: Total precipitation, days with rain, degree days, and average air temperature
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Pre-season risk - Results
Precipitation and temperature of Dec – Feb most significant explanatory weather factors
Parameter Estimate
Total Precipitation (December) -0.007
Total Precipitation (January) -0.014
Total Precipitation (February) -0.008
Sum of monthly average temperature (December, January & February)
0.14
* Magnitude of effect different for counties
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Pre-season risk – “county effect”
►Correction between counties?
(Structured heterogeneity)
► Other missing factors?
(Unstructured heterogeneity)
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Investigate the “county” effect: Bayesian disease mapping
yi ~ Bin (ni, pi) (likelihood)
pi = f (T, Pr) + Ui + Vi
Structured (autocorrelation)
“Auto-regression function”
Unstructured
N (0, σ2)
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• Structured heterogeneity? NO
• Unstructured heterogeneity? YES
Pre-season risk – “county effect”
Sampson co.
TSWV incidence
Pro
bab
ilit
y o
f T
SW
V i
nci
den
ce
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Validation (2008 – present)
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Predicted Pre-season riskNorth Carolina - 2008
County Station Predicted
Craven Havelock 14 – 22Duplin Mount Olive 4 – 9 Sampson Clinton 13 – 26Lenoir Kinston 4 – 11 Pitt Ayden 1 – 4 Johnston Clayton 0.6 – 3.5Wilson Sims 0 – 1
Reported
14
8
2
10
2.3
4
1
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Predicted Pre-season riskNorth Carolina - 2010
County Station Predicted
Craven Havelock 1 – 14 Duplin Mount Olive 1 – 5 Sampson Clinton 0.5 – 10 Lenoir Kinston 1 – 12 Pitt Ayden 0 – 3 Johnston Clayton 0 – 0.5 Wilson Sims 0 – 1
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Conclusions
• Winter weather good predictor of TSWV risk for upcoming season
* Importance of spring weather was not discussed…
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Pre-season risk on the web
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Expand effort - 2009
• Pre-season risk
(Georgia, North Carolina, South Carolina and Virginia)
• In-season risk
(Georgia, North Carolina, South Carolina)
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• K. Cherry
• J. Radcliff & M. Browne
• NC Tobacco Agents
• NC Tobacco Research Commission
• Tobacco Education & Research Council
Acknowledgements