Age-stage, two-sex life table of Parapoynx crisonalis (Lepidoptera: Pyralidae) at different temperatures

Parapoynx crisonalis is an important pest of many aquatic vegetables including water chestnuts. Understanding the relationship between temperature variations and the population growth rates of P. crisonalis is essential to predicting its population dynamics in water chestnuts ponds. These relationships were examined in this study based on the age-stage, two-sex life table of P. crisonalis developed in the laboratory at 21, 24, 27, 30, 33 and 36 degrees C. The results showed that the values of S-xj (age-stage-specific survival rate), f(xj) (age-stage-specific fecundity), l(x) (age specific survival rate) and m(x) (age-specific fecundity) increased as the temperature rose from 21 to 27 degrees C, then decreased from 30 to 36 degrees C. Temperature also had a significant effect on the net reproductive rate (R-0), gross reproductive rate (GRR), intrinsic rate of increase (r) and finite rate of increase (gimel.). The value of these parameters were at low levels at 21, 33, and 36 degrees C. Further, the r value decreased as the temperature rose from 24 to 30 degrees C, while the GRR reached its highest level at 27 degrees C. The results indicated that optimal growth and development of P. crisonalis occurred at temperatures between 24 degrees C to 30 degrees C when compared to the lowest temperature (21 degrees C) and higher temperatures of 33 degrees C and 36 degrees C.