Seasonal fluctuation of Banana leaf and fruit scarring beetle, Nodostoma subcostatum (Jacoby) (Coleoptera: Chrysomelidae) in terai region of West Bengal

Studies on seasonal fluctuations of Banana leaf and fruit scarring beetle in terai region of West Bengal revealed that the pest was active and caused damage throughout the year, highest population (39.83 beetle/plant) and scars (60.65 scars/20 cm² leaf area) were observed during second week of August in both the year. Population of beetle and scars started decreasing from September onwards and reached lowest (5.50 beetle/plant and 7.03 scars/20 cm² leaf area) in last week of December, due to gradual decrease of temperature. In case of fruit, maximum infestation (120.10 scars per fruit) noticed in 3^rd week of august. Population and scar production on leaves as well as fruit had positive and significant correlation with maximum and minimum temperatures, morning and evening relative humidity and weekly total rainfall. Whereas the humidity temperature ratio and bright sun shine hours exhibited non-significant negative correlation with the population and scar development on leaves but in case of fruit infestation HTR had non-significant negative correlation and bright sunshine hours exhibited non-significant positive correlation. Further weather parameter during winter (low temperature and low humidity) was responsible for low population of the beetle and no of scars/20 cm² leaf areas.