The development time of different stages of Sesamia nonagrioides Lefevbre w
as studied in the laboratory at constant temperatures in the range 10-36 de
greesC. The relationship between the developmental rate (1/d) and the tempe
rature (degreesC) was determined using both linear and nonlinear (Logan typ
e III) models. The fit of the linear regression in the temperature range 15
-27.5 degreesC and Logan type III equation was good (R-2 > 0.97). The lower
developmental threshold, calculated using the linear model, was t(b) = 12
degreesC. The nonlinear model gave a higher threshold of T-max = 36 degrees
C, and an optimal developmental temperature of T-max = 30 degreesC. The nig
hts of S. nonagrioides were studied in Lleida, Spain, from 1984 to 1997, an
d the number of degree-days required for their occurrence was calculated. A
relationship between the degree-days required for the first night calculat
ed ly the averaging method and the degree-days required for estimated diapa
use termination was obtained (R-2 = 0.84). This relationship allowed the pr
ediction of the first night occurrence in the field. The degree-days requir
ed for the second and third generations were then calculated as 730 and 491
, respectively.