Survivorship assessment for Spodoptera littoralis susceptible and field population after insecticide sublethal dose treatment

Abstract

Spodoptera littoralis (Lepidoptera noctuidae) (Boisd) is the most economic and series pest in Egypt with highly fecundity and dangerous attacking many crops. Insecticide efficiency trials showed failure and need more investigation periodically by many subject area. Susceptible laboratory reared population and field collected batches were subjected to bioassay of time mortality of the life survivors recording is the data producer by treating larvae with sublethal dose (LC30) of insecticides candidates for this testing. Time-mortality data are improved method involves proportional survival and hazards modeling, known as Cox regression. The survival analysis of S. littoralis treated with sublethal dose of some insecticides exhibit slight differences in the median survival time (LT50) observed for each insecticide, where the higher values was 224.4 hour for metaflumezone and the smallest was 170.1 for pyridalyl in susceptible population while in field, the higher was 336 for indoxacarb and the smallest was 144 hour for imidacloprid. The median survival time was 265 for susceptible control and 375 hour for field control. Log rank test exhibit significant differences among treatments for susceptible (Log-rank test, Z = 259.91, d.f. = 4, p