Effect of weather parameters on the incidence of H. armigera
The data presented in Table 1 and Fig 1,2 revealed that the larval population of
H.
armigera first appeared in the third and fourth week of January during
rabi, 2014-15 and 2015-16, respectively. Initially only 0.3 and 0.9 larva per meter row length (mrl) were recorded during
rabi, 2014-15 and 2015-16, respectively. The present results are in agreement with those of
Lal (1996),
Reddy et al., (2009) and
Dhaka et al., (2011), who reported activity of larvae of
H.
armigera during the months of January and February. The larval population increased gradually after appearance with the vegetative growth of the chickpea and attained its peak in the fourth week of February (5.8 larvae per mrl) during
rabi, 2014-15 and third week of February (6.0 larvae per mrl) during
rabi, 2015-16; there after, population declined abruptly. The results corroborate the findings of
Gupta and Chandel (2008),
Dhaka et al., (2011), Pandey et al., (2012), Sharma et al., (2012) and
Shinde et al., (2013) who reported peak period of larval infestation in last week of February and beginning of March.
Correlation between weather parameters and larval population of H. armigera
The correlation studies (Table 2) revealed that during first year (
rabi, 2014-15) the larval population showed non-significant positive correlation with maximum temperature and minimum temperature (r=0.022 and 0.163, respectively). These results corroborates with findings of
Krishna et al., (2007), Gupta and Chandel (2008),
Reddy et al., (2009), Sharma et al., (2012) and
Mahawar et al., (2015), who reported positive non-significant correlation with larval population and temperature. During second year (
rabi, 2015-16), the significant positive correlation was also existed between larval population and maximum and minimum temperature (r=0.884 and 0.898).
Kulhari and Singh (2008),
Pandey et al., (2012), Shinde et al., (2013) and
Yadav et al., (2016) also computed significant positive correlation between larval population and temperature, which supports the present findings.
Maximum relative humidity showed negative non-significant (r=-0.110) and significant correlation (r=-0.761) with larva population during first and second year, respectively, while minimum relative humidity showed significant negative correlation during both the years (r=-0.588 and -0.582, respectively). The present finding confirms with the results of
Pandey et al., (2012) and
Sharma et al., (2012) they recorded negative non-significant correlation between larval population and relative humidity.
Umbarkar et al., (2010), Wakil et al., (2010) and
Mahawar et al., (2015) computed negative significant positive correlation with larval population and relative humidity; these findings are also supports present findings.
Rainfall showed significant and non-significant positive correlation (r=0.807 and 0.115) with larva populationduring first and second year, respectively. The present results corroborates with the findings of
Gupta and Chandel (2008),
Kulhari and Singh (2008) and
Kumar et al., (2015), who also found positive non-significant correlation between larval population and rainfall.Sunshine hours showed non-significant and significant positive (r=0.010 and 0.868) correlation during first and second year, respectively.
Mahawar et al., (2015) recorded positive non-significant correlation with sunshine hours and larval population which supports the present findings.
Regression analysis between larval population of H. armigera and weather parameters
The regression equation was computed by taking of larval population of pod borer as dependent variable and other weather parameters as independent variable. It was evident from the study that none of the weather parameters were alone responsible for larval population of pod borer on chickpea (Table 3). All weather parameters collectively accounted for 81.30 and 52.20 per cent variability in larval population of pod borer during 2014-15 and 2015-16, respectively.
