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Spatial and Temporal Distribution of Iris yellow spot virus and Thrips in Colorado Onion Fields


Tables 1 and 2 from:


Schwartz, H. F., Gent, D. H., Fichtner, S. M., Khosla, R., Mahaffey, L. A., Camper, M. A., and Cranshaw, W. S. 2010. Spatial and temporal distribution of Iris yellow spot virus and thrips in Colorado onion fields. Online. Plant Health Progress doi:10.1094/PHP-2010-0820-01-RS.



Table 1. Summary of field, plant, edaphic, thrips and Iris yellow spot virus data (low to high) collected from six onions fields in western and northeastern Colorado during 2005 and 2006.

Variable 2005 2006
Loma-
North
Loma-
South
Peckham
seed
Peckham
transplant
Fort
Collins
Peckham
Field size (ha) 4.0 4.2 13.3 3.2 6.1 20.0
No. of sample sites
(0.2 ha grid)
21 24 67 16 34 56
Plant stand
(plants/3 m bed)
48.2 60.4 -- 48.7 55.7 83.7
IYSV incidence –
season (%)
0-7.0 0 2.3-97.2 73.5-100.0 0 0-56.6
IYSV-rAUDPCw 0-0.0259 0-0.0081 0.0020-0.5120 0.4409-0.8754 0 0-0.2830
No. of thrips-season
(total of 1st to last
sample/plant)
4.6-64.4 8.2-103.8 30.0-570.0 100.0-374.0 12.8-30.8 1.1-11.4
Thrips-tDaysx 0.09-1.26 0.13-1.62 0.18-3.35 2.22-6.94 0.41-0.99 0.06-0.57
Total marketable
yield (MT/ha)y
4.5-54.4 0.7-32.0 0.6-23.5 14.4-52.0 8.3-29.1 0.1-35.5
Soil texturez CL, L, SiL CL, L, SiL LS, SL SL SL SL
Soil pH 7.7-8.2 7.7-8.4 6.1-7.4 5.7-7.0 7.7-8.1 7.3-8.1
Organic matter (%) 1.0-1.3 1.1-1.6 0.8-1.4 0.8-1.5 1.1-1.8 0.5-1.9
Soluble salts 0.5-4.8 0.5-3.6 0.3-0.8 0.0-0.6 0.6-3.9 0.2-0.9
Nitrogen (ppm) 20-523 12-124 9-96 13-103 4-139 3-88
Phosphorous (ppm) 11-33 10-39 30-146 32-76 5-39 24-169
Potassium (ppm) 85-136 96-150 102-363 137-359 149-379 136-653
Magnesium (ppm) 218-323 153-334 137-313 160-269 533-1084 95- 383
Calcium (ppm) 3454-4657 3438-8067 802-1762 922-1569 2142-4419 558-1997
Sulfur (ppm) 26-495 25-999 17-80 24-54 240-999 6-67
Zinc (ppm) 1.0-2.5 1.1-2.4 4.2-15.8 4.8-16.3 0.6-1.4 2.0-30.7
Manganese (ppm) 1.3-3.2 0.9-3.4 0.8-46.4 1.4-46.4 4.1-11.5 4.6-19.8
Copper (ppm) 1.4-3.0 1.5-2.5 2.6-11.5 3.6-11.5 0.9-1.8 1.5-13.8
Iron (ppm) 6.8-12.9 8.8-24.4 16.4-52.7 19.7-46.3 5.4-12.8 17.6-53.6
Boron (ppm) 0.8-1.1 0.8-1.0 0.7-1.1 0.7-1.0 1.8-3.4 0.7-2.1
Sodium (ppm) 112-1189 98-218 75-208 111-162 108-475 71-230
% potassium
(base saturation)
1.1-1.5 0.7-1.8 3.4-11.1 4.1-8.2 2.5-3.8 5.5-11.2
% magnesium
(base saturation)
9.1-10.3 3.0-12.6 15.9-23.0 14.9-19.9 19.3-32.5 17.8-21.4
% calcium
(base saturation)
73.9-87.2 83.2-95.2 55.0-73.6 59.6-71.9 57.5-74.6 63.1-70.0
% sodium
(base saturation)
2.4-16.4 1.0-3.9 4.0-9.8 4.0-7.5 1.9-7.3 2.8-7.3
% hydrogen
(base saturation)
0 0 0-13.4 0-13.4 0 0
CEC 20.0-31.5 11.5-42.3 5.8-13.0 7.6-12.0 18.0-32.8 5.2-14.9

  w Relative area under the disease progress curve (rAUDPC) = AUDPC values divided by the total area of the graph (21). AUDPC = ∑[(xi+n1 + xi)/2] [ti+1+1 – ti)] where xi is incidence of IYS at the ith observation, ti = time in days at the ith observation, and n = total number of observations. IYS incidence measured as number of symptomatic/total plants in a 3-m section at each sampling point.

 x t-days = Thrips-days calculated by dividing the average number of thrips/plant by the number of days between the first and last sample for each experiment (38).

 y Total marketable yield = combined weight of medium, jumbo, and colossal bulbs (32).

 z CL = clay loam, L = loam, LS = loamy sand, SL = sandy loam, SiL = silt loam. Soil texture for 2006 was obtained from Soil Survey Staff (39).



Table 2. Pearson’s correlation coefficients for plant population, yield, thrips density, Iris yellow spot disease incidence, and edaphic characteristics for six commercial onion fields in western and northeastern Colorado during 2005 and 2006.

Edaphic
factor
Plant
population
v
Yieldw Thrips-
days
x
IYS
incidence
y
rAUDPCz
% organic matter -0.08  0.21 -0.07 -0.37* -0.27
Nitrogen -0.32  0.10  0.20 -0.06 -0.03
Bray 1 P  0.57** -0.37*  0.01  0.24  0.19
Potassium  0.41** -0.19 -0.15 -0.02  0.01
Magnesium -0.21  0.32 -0.03 -0.38* -0.31
Calcium -0.45**  0.41** -0.15 -0.54** -0.44**
Sulfur -0.32  0.34  0.06 -0.29 -0.23
Zinc  0.47** -0.34 -0.01  0.36*  0.32
Manganese  0.16 -0.21 -0.02  0.28  0.29
Copper  0.32 -0.23  0.01  0.44**  0.43**
Iron  0.38* -0.37  0.18  0.53**  0.48**
Boron  0.08  0.14 -0.16 -0.35 -0.30
Soil pH  0.20  0.11 -0.44** -0.61** -0.56**
Salts -0.42**  0.35*  0.11 -0.32 -0.27
Sodium -0.28  0.19  0.04 -0.22 -0.17
% potassium  0.54** -0.44** -0.01  0.36*  0.31
% magnesium  0.16 -0.06  0.11  0.09  0.06
% calcium -0.27  0.25 -0.20 -0.40** -0.37*
% sodium  0.07 -0.19  0.25  0.40*  0.33
% hydrogen -0.17 -0.03  0.23  0.40*  0.47**
CEC -0.44**  0.42** -0.13 -0.53** -0.43**

 x Number of onion plants/3 m of one row/sample site/field.

 w Yield of colossal and jumbo grade bulbs estimated from 3 m of one row/sample site/field.

 x Thrips-days were calculated as:

n [(xi+1 + xi)  / 2] [ti+1ti]
i=1

    where xi is the mean number of thrips/plant at time ti.

 y Incidence (%) of plants with iris yellow spot (IYS) symptoms on the final disease assessment near crop maturity.

 z rAUDPC is relative area under the disease progress curve (21). rAUPDC was calculated as:

{ ∑ n [(xi+1 + xi)  / 2] [ti+1ti] } / tnti
i=1

    where xi is IYS incidence at time ti.

   * = significant at P < 0.05.

 ** = significant at P < 0.01.




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