Biochemical factors associated with mango mealy bug (Drosicha mangiferae G.) infestation in different mango cultivars at Malda, West Bengal (India)

Five different popular mango cultivars (Fazli, Guti, Lakhanbhog, Gopalbhog and Langra) of Malda, West Bengal, India were screened for the mango mealy bug (Drosicha mangiferae G.) population in panicle and trunk throughout the pest infestation period during 2018 and 2019. The average pest number at peak time (13 Standard Meteorological Week or SMW) of infestation indicated that maximum pest number of 132.57 and 28.05 was noted in the 30 cm branch of inflorescence and 10 cm2 area of the trunk in Fazli cultivar. Whereas, minimum number of 20.27/ 30 cm branch of inflorescence and 6.36 in the same area of trunk was found in Langra. Study of various biological parameters of mealy bugs also indicated the the order of infestation of the five cultivars as Fazli>Guti>Lakhanbho g>Gopalbhog>Langra. Analysis of various biochemical parameters revealed that there was a significant positive correlation between pest density phagostimulants like sugar, protein, moisture and nitrogen. Significant negative correlation was observed between pest number and alkaloid, flavonoid, phenol, tannin, ascorbic acid as well as crude fibre suggesting their pivotal role in low pest incidence. By considering the adjusted R2 in stepwise multiple regression model, it was noticed that tannin was the most significant factor (39.2 %) followed by nitrogen (15.5 %), flavonoid (11.4 %), phenol (7.7 %), ascorbic acid (6.9 %) and protein (6.2 %) to influence pest number. Factors like moisture (1.0 %), sugar (2.7 %), antioxidant (1.0 %) had minor contributions. Therefore, it can be concluded that a combination of factors influence pest density and a single factor is not adequate to affect the pest population. The study is helpful in understanding the host preference of mealy bug.