Degree-day models for emergence and development of the rice water weevil (Coleoptera: Curculionidae) in southwestern Louisiana

The rice water weevil, Lissorhoptrus oryzophilus Kuschel, is the most destructive insect pest of rice in the United States. Degree-day (DD) models were developed to predict the emergence date of adult rice water weevils from overwintering in the spring and to describe larval and pupal development on two varieties of rice under field conditions. The model that best described emergence of weevils from overwintering was derived from 14 yr of light trap captures. The temperature threshold for the best-fit model was 15.6°C, the start date for the model (date at which degree-day accumulation begins) was 33 d after 1 January, and the end point for the model was a cumulative light trap capture of six weevils. By using these parameters, emergence of weevils occurred after accumulation of 139.2 DD (°C x day). The model predicted emergence of weevils in 2001, 2002, 2003, and 2004 with an error of 4, 7, 1, and 2 d, respectively. For the model describing larval development, the number of degree-days required for development from egg to 50% pupation was 359.1 ± 19.4DD (°C x day) with a low temperature threshold of 10°C. The number of degree-days required for pupal development was 264.3 DD (°C x day), and the total degree-days required for development of one generation was ≈623.4 DD (°C x day). Larval development did not differ on cultivars 'Jefferson' and 'Bengal'.