Degree-day model for development and incidence of lucerne weevil, Hypera postica (Gyllenhal) in central India.

摘要

A degree-day model was developed for weevil (H. postica) on lucerne (cv. RL-88) grown in Jhansi, Uttar Pradesh, India, during the rabi seasons of 2004-07. The hatching of the eggs, which was completed in approximately 10 days, required 62 degree-days. The larval period, which consisted of 4 instars, required 160 degree-days. The pupal period lasted approximately 11 days and required 99 degree-days. Thus, the total degree-day requirement from egg stage to adult stage was 321, and this process lasted approximately 49 days in India. The weevil population with respect to degree-day accumulation during the crop growth period was also investigated. The earliest degree-day accumulation was observed on 1 December. As the accumulation of degree-days proceeded, the larval population increased and attained the peak value (ranging from 121.2 to 141.4 larvae/ft-1) on the first week of February. During this period, lucerne showed significant defoliation. The larval population then gradually decreased and by the third week of March, the larval population was low (<30 larvae/ft-1). A second-order polynomial model described the relationship between weevil population and accumulated degree-days.