2021, Vol. 2, Issue 1, Part A
Survivorship assessment for Spodoptera littoralis susceptible and field population after insecticide sublethal dose treatment
Author(s): Hanan Salah El-Din Taha
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<0.001) and field (Log-rank test, Z = 297.48, df. = 4, p<0.001). Hypothesis testing were computed for testing the survival curves, and every two hazard rates equality, at all times less than the maximum observed. Survival curves within insecticide groups and within population and control were differ according to p-values are less than 0.05, verify the null hypothesis is success to be rejected. Some hazard rates decreases with time in both population. The hazard ratios of insecticides in relation to control was 95% confidence intervals of the susceptible and field calculated were smaller than one prove great indication that field population were dying at a significantly slower rate than susceptible, and males population of some insecticides have more chance to die at any point in time more than males from the susceptible. The results for field population were achieved only 1% of population survived at 555 hour, from 20 to 30 % at 336 hour, from 30 to 40% and from 40 to 50 % after treatment for all pesticide tested, where population stages were old moths, emerged moth, pupae and 5th instar larvae respectively. This result evidenced that all insecticide tested at low concentrations treatment through a long period of exposure, must stimulate a continuous mortality and the time mortality assay using Kaplan–Meier and Cox regression analysis methodology were accurate and provide clear decision about pesticide toxicity, efficiency status and differences.
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How to cite this article:
Hanan Salah El-Din Taha. Survivorship assessment for Spodoptera littoralis susceptible and field population after insecticide sublethal dose treatment. Acta Entomol Zool 2021;2(1):61-72. DOI: 10.33545/27080013.2021.v2.i1a.32