Studies on seasonal incidence of leaf webber, Spoladea recurvalis F. and Spodoptera litura F. on amaranthus (Amaranthussp. L)

Abstract

Seasonal incidence of leaf webber. Spoladea recurvalis F. and Spodoptera litura F. on amaranthus (Amaranthussp. L) was studied during 2017-18 in Tamil Nadu, India. The incidence of leaf webber was recorded throughout the season, the infestation was observed from the first week of observation (1 SMW) but a considerable larval population was recorded from the 05th SMW to the 10th SMW with the range of 1.22 to 2.31 larvae/ plant. The infestation of leaf caterpillars was observed from the 1 SMW and the incidence increased from the 5th SMW (0.15 larvae/plant) and reached a peak during the 10th SMW (1.14 larvae/plant). The fluctuation in the incidence of leaf caterpillars occurred throughout the survey. The correlation between the leaf webber incidence and weather parameters revealed that leaf webber incidence had a strong negative correlation with rainfall (-0.445") and minimum temperature (-0.286) and had a non-significant negative correlation with minimum temperature (-0.238NS) whereas leaf webber non-significantly positively correlated with relative humidity (-0.175NS). The leaf caterpillar had a significant negative correlation with maximum temperature (-0.346"), minimum temperature (-0.487"). and rainfall (-0.303") whereas significantly positively correlated with relative humidity (0.348").