Trends in Biosciences

The seasonal occurrence of sucking pests was similar on Bt, stacked Bt and non Bt cotton hybrids. The initial incidence of aphids was recorded on 34^th standard week (4^th week of August) and the peak incidence was observed from 39^th standard week (4^th week of September) to 46^th standard week (3^rd week of November). The leafhoppers incidence showed increasing trend from 39^th standard week onwards crossing ETL from 42^nd to 47^th standard week (2^nd week of October to 3^rd week of November). While the peak incidence was on 35^th to 37^th standard week for thrips and 44^th to 48^th standard week for white flies. The incidence of sucking pests was slightly high in stacked Bt, Bt versions compared to non Bt versions but the differences were non significant. The incidence of aphids recorded in all the stacked Bt, Bt and non Bt hybrids had positive correlation with all the weather factors except maximum temperature which showed significant negative correlation. All the major weather parameters showed positive correlation with the population of leafhoppers except maximum temperature with significantly positive correlation with relative humidity and rainfall. Thrips showed highly significant positive correlation with maximum temperature, minimum temperature, evening relative humidity and rainfall. There was significant negative correlation with maximum temperature on the white flies population. The total influence of all the weather parameters was high and significant on the leaf hoppers (59.10%) and thrips (80.5%), while it was non significant on aphids and white flies population.