BLACKHEADED FIREWORM (LEPIDOPTERA, TORTRICIDAE) LARVAL PHENOLOGY MODEL-BASED ON DIET-SPECIFIC DEVELOPMENTAL RATES

Phenology of blackheaded fireworm larvae, Rhopobota naevana (Hubner), was simulated with developmental rate-summation models. The relationsh ip between temperature and median developmental rates of third instars and pupae were determined by using linear splines. Variation in devel opmental rates within a population was determined by using Weibull fun ctions. Phenology of summer-generation larvae was simulated in multipl e weekly cohorts starting from the estimated times eggs were laid. The model predicted within an average of 1 d (sigma = 3.6 d) the date whe n 50% of the larvae in the field were past the second stadium. Develop ment of larvae in the spring was predicted starting from the time of h atch of sampled eggs. The model included lower developmental rates and higher mortality before new leaves were available. When diet was incl uded in the model, it predicted the date when 50% of the spring-genera tion larvae was past the second stadium within an average of 2.5 d. Th e models for the spring and summer generations were sensitive to the e stimated dates of egg hatch and oviposition, respectively.