The survival and biological characteristics of Oryzaephilus surinamensis L. (Coleoptera: Silvanidae) in the feeding conditions on three date palm cultivars

Abstract

The Saw-toothed grain beetle, Oryzaephilus surinamensis L. is a stored product pest that 7 imposes significant damages on the dried and semi-dried date fruits. The current study aimed to the 8 investigate the effects of diets on the biological parameters of the adults and the larvae of O. surinamensis. Two groups of individuals were fed to the three diets containing Sayer, Zahedi and 10 Deiri date cultivars, and monitored at temperature 27 ± 5 °C with relative humidity 60 ± 5% in the 11 growth chamber. The daily mortality of O. surinamensis was recorded in each cultivar separately to 12 analyse survival and hazard function determination through Gompertz, exponential, Weibull, and 13 logistic models. The results showed that survival and hazard functions of the larvae and the adults 14 had the most appropriate fit with Weibull and exponential models for all date cultivars. In the first 15 three to four days of experiment, the risk rate was low in all the three cultivars. The effect of nutrition 16 on the larvae and the adults showed similar trends but with different coefficients on the three dates cultivars. During the 12-day period, survival decreased gradually and the hazard rate increased as well. The slope of life expectancy changes and risk rates for the larval stages were steeper than adults 19 on all cultivars. The highest and the least slope of the speed of changes were observed in the larvae 20 and the adults fed on Deiri and Zahedi cultivars, respectively. There were significant differences 21 between the mean growth rate, fertility index and vital index as the highest values were recorded in 22 Deiri cultivar. These findings confirmed that selection of the date cultivars for feeding by adults is in 23 a way to ensure higher larval survival rates.