INTRODUCTION
The fungal seed born disease popularly known as Karnal bunt is generally
expressed as a cool winter/spring weather disease in the North. The
weather conditions during the susceptible period are critical factors
in bunt development. An average temperature range of 18 °C to 22 °C,
coupled with high relative humidity (morning) or the day relative
humidity, is considered optimum for infection. In the study of various
diseases, it appearance in or over the crops, plants, trees and its
economical product parts or grains of the crops i.e. wheat, field crops
and other which were influenced by the weather condition along with the
crucial parameters. The weather fluctuation and variability and
environment condition will be play the very crucial role to create the
optimum favourable condition and resulted to cause the infestation. Long
term weather parameters were analyzed i.e. temperature, relative
humidity, radiation and rainfall from 1st to
12th standard meteorological weeks but
6th to 12 SMWs are favored to development of the grain
infestation disease. Workneh et al. (2007) studied the weather variables
(temperature and rainfall amount and frequency) were collected and used
as predictors in discriminant analysis for classifying bunt positive and
-negative fields using incidence data for 1997 and 2000 to 2003 in San
Saba County. Due to western disturbance in the North West part of the
country were received the periodically rainfall to maintained the high
level of relative humidity (Singh et al ., 2018). The higher level
of relative humidity that can be maintained the higher humidity within
the crop canopy and favored the fungal growth might be due to the
increasing leaf or canopy wetting period. The momentum within the crop
canopy will be reduced so higher level of humidity will be maintained.
The simple linear regression model showed that the maximum temperature
and morning relative humidity had maximum influence on the development
of leafhopper population. The stepwise linear regression model was
explained the coefficient of determination (R²) of leafhopper population
with the range 40 to 90 per cent in respective year (Janu et al.,2018). sStansbury and McKirdy (2002) reported that there was a strong
correlation (r :0.83) between the Humid Thermal Index (HTI) model,
which used long-term, average-monthly data, and the rainfall model,
which was based on the per cent chance of at least three Suitable Rain
Events (SRE) during the susceptible period (August to October). Results
suggest that northern wheat growing areas are too hot and dry
(HTI<2.2, chance of SRE 15–27%), southern areas are marginal
to too cold and/or wet (HTI > 3, chance of SRE 68–97%),
eastern areas are marginal to too hot and dry (HTI around 2.2, chance of
SRE 24–50%), and western areas are suitable (HTI between 2.2 and 3.3,
chance of SRE 41–78%).