Forewarning Rice Blast in India

Forewarning Rice Blast in India
Table 10. Regression equations based on step-down regression of one week
preceding weather data (Andhra Pradesh)
Year Equation R R 2
LEAF BLAST
DRR, 2002 Y = 43.287 - 2.859** T + 0.354** Rh + 1.635** L Min E W 0.854 0.729
DRR, 2003 Y = -1537.742 + 13.589** T + 13.413** T - 6.197** R Max Min W
+ 9.431** Rh + 1.758 L M W
0.858 0.735
Medchal, 2001 Y = -19.618 + 1.241* T + 0.348** Rf Min 0.678 0.459
Medchal, 2002
NECK BLAST
Y = - 88.021 + 0.925** Rh +2.908** R M W 0.785 0.616
DRR, 2002 Y = 128.885 -1.968** T - 0.98 Rh + 0.18* Rh + 1.499* L Min M E W 0.945 0.894
DRR, 2003 Y = - 155.37 + 8.493** T - 8.061** T + 3.82* R + 0.924 Rh Max Min W E 0.929 0.864
Medchal, 2001 Y = - 259.522 + 8.86** TMax 0.376 0.141
Medchal, 2002 Y = 34.684 - 1.403 T + 0.602** Rf Min 0.673 0.453
T Max = Maximum temperature, T Min = Minimum temperature, Rf = Rainfall, R W = Rainy days per week,
Rh M = Relative Humidity in morning, Rh E = Relative humidity in evening, L W = Leaf wetness, Y = Disease
variable, R = Multiple correlation coefficient, R 2 = Coefficient of determination.
In general, the step-down multiple regression analysis shows, the minimum
temperature, morning relative humidity, rainy days per week, followed by evening
relative humidity, leaf wetness, maximum temperature and rainfall were found
significant weather factors for the leaf blast development, while both minimum and
maximum temperature, rainy days per week followed by the intensity of rainfall and
leaf wetness were found to have significant effect on neck blast incidence.
This clearly indicates that minimum temperature, morning relative humidity
and rainy days / week increased the leaf blast severity, while the minimum and
maximum temperature and rainy days / week increased the neck infection under
natural conditions, and so these may be selected as contributing factors for prediction
of leaf and neck infection in nature.
Himachal Pradesh:
Field trials on rice blast progress in relation to weather were laid out at three
locations in Himachal Pradesh, viz., Palampur, Malan and at the farmers’ fields (Arla
and Pharer). At Palampur, trials were conducted at different dates of transplanting on
a susceptible variety Himalaya 2216, at Malan only one date of transplanting was
done and at farmers’ fields, a local susceptible variety was transplanted. Data on
leaf blast and neck blast were recorded as per Standard Evaluation System for Rice
(IRRI, 1996).
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