Seasonal Variation in Incidence of Insect Pests Occurring on Black Gram [Vigna mungo (Linn.) Hepper] in Lower Gangetic Plains of West Bengal

Abstract

The experiment was conducted in the 'A-B' Block Farm of Bidhan Chandra Krishi Viswavidyalaya situated at Kalyani, Nadia, West Bengal during both summer and kharif seasons of 2016 with an objective to study the seasonal variation in incidence of insect pests on two varieties of black gram viz. Pant U-31 and Pant U-19 as well as their relationship with abiotic factors in the lower Gangetic plains of West Bengal. The results revealed Aphis craccivora, Bemisia tabaci, Megalurothrips distalis, Maruca vitrata, Helicoverpa armigera, Spilarctia obliqua as the major pests of the crop. Whitefly population on black gram reached its peak in 5 WAS in both the seasons. Maximum aphid population has been recorded in 6 WAS and 7 WAS during summer and kharif seasons, respectively. Flower thrips was recorded highest 9 WAS during both the seasons. Gram pod borer population has been recorded maximum in 8 WAS and 7 WAS during summer and kharif seasons, respectively. Spotted pod borer population reached its peak in 10 WAS in both the seasons, while, hairy caterpillar population has been recorded highest in 5 WAS in both the seasons. In black gram, whitefly population was significantly and negatively correlated with both temperatures irrespective of season, however, it was significantly and positively correlated with minimum relative humidity in summer season, but it was negative correlation during kharif season. Both the temperatures were significantly and positively correlated with aphid population during summer, but during kharif minimum temperature only was positively correlated with the pest population. In case of flower thrips, the pest population was significantly and positively associated with minimum relative humidity during summer season but the association was reverse during kharif season. The correlation of gram pod borer population in black gram with all the weather parameters were found non-significant irrespective of season and crop variety. Spotted pod borer population significantly and negative correlated with maximum temperature during both seasons, however, a significant and positive correlation with minimum relative humidity and rainfall, negative correlation with minimum temperature during summer and positive correlation with bright sunshine hour were also observed. Significantly negative correlations were found with hairy caterpillar population and both the relative humidity and rainfall, while, the association was significantly positive with both the temperature and bright sunshine hour during summer.

Evaluation of IPM module against major insect pests of green gram, Vigna radiata (L.) Wilczek in lower Gangetic plains of West Bengal

“…Observations were taken during early morning hours when most insects are less active. Data on insect pest population in test plot was recorded following the methodology adopted by Biswas (2017). Afterwards, the mean population was calculated.…”

“…This classification is expedient in judging the economic importance of the pest, especially their impact on seed yield and to work out control measures. Among the 64 species of insect pests reported on the green gram (Siddadappaji et al, 1979), the aphid (Aphis craccivora), whitefly (Bemisia tabaci), flower thrips (Megalurothrips distalis), spotted pod borer (Maruca vitrata), gram pod borer (Helicoverpa armigera), plant bug (Riptortus pedestris), pod bug (Clavigralla gibbosa) and blue butterfly (Catochrysops strabo) were found to be the major insect pests in West Bengal condition (Biswas and Banerjee, 2019). In most cases, farmers are not interested to take any control measures for the insect pests due to their less return (Machocho et al, 2012).…”