Effect of meteorological parameters and natural enemies on population dynamics of rose aphid, Macrosiphum rosae L. under mid hills of Himachal Pradesh, India

The study revealed that the rose aphid first appeared in 8th standard meteorological week (SMW) and attained the first peak on 10th SMW, when maximum and minimum temperatures were around 20.5 and 5.9 (°C), respectively and morning relative humidity was 62.50% during both the years. The second mean population build-up was observed on 36th SMW and the population fluctuated between 37th to 52nd SMW and peak population was recorded on 51st SMW (29.05 aphids/shoot), which declined to 1.48 aphids/shoot on 52nd SMW during both years. The rose aphid population was significantly negatively correlated with T_max (r = -0.453**) and T_min (r = -0.572**); whereas relative humidity (morning and evening) and rainfall showed a nonsignificant negative correlation with the rose aphid population. The stepwise regression analysis of rose aphid population with weather parameters showed that the maximum temperature contributed 20.50% variation in rose aphid population followed by morning relative humidity (17.90%) and minimum temperature (12.70%). The difference between coefficient of multiple determination (R²) and adjusted R² was less, indicating that the abiotic variables (T_max: 0.017; T_min: 0.030) have a significant effect on the rose aphid population. Hence, this study gives information on abiotic and biotic factors that naturally suppress the rose aphid, which helps develop management strategies against M. rosae in the mid-hills of Himachal Pradesh, India.