Study of Thermal Requirements for the Development of Two-Spotted Mites Tetranychus urticae Koch (Acariformes: Tetranychidae), Reared on Castor Leaves (Ricinus communis L.) Under Laboratory Conditions

Abstract

The two-spotted spider mite Tetranychus urticae Koch (Acariformes: Tetranychidae) is an important pest affecting several important oil crops in Iraq. The aim of this study was to determine the minimum temperature and calculate the necessary heat units for the time of development of the duration of these mites stages. The application was carried out in incubators with different temperatures (10, 15, 20, 25, 30, 35 and 40 +2 °C), relative humidity (50-60 +5%) and light: 8: 16 hours dark period on the lower surface of the grown castor leaves. newly. The results showed that the development time of the egg incubation, the larval stage, the first nymphal(protonymph) stage (active + quiescence), and the second nymphal (deutonymph) stage (active + quiescence) at temperatures 15, 20, 25, 30, and 35 °C. It decreased gradually with increasing temperature. Moreover, the egg incubation period was 8.533 and 2.067 days, the larval stage (active + quiescence) 5.821 and 1.298 days, the first nymph (protonymph) (active + quiescence) 5.521 and 1.309 days, and the second nymph (deutonymph) (active + quiescence) 5.417 and 1.150. days to the effect of 15 and 35 degrees Celsius. In addition, the development time from egg to adult was 24.972 and 5.833 days at 15 and 35 °C, respectively. The temperature threshold was 9.763, 10.693, 9.543, 10.314, and 9.957 degrees Celsius, respectively. Finally, the accumulated heat units required for the growth time of each mite cycle differed according to the different temperature threshold and growth time and the mite could not grow and develop at 10 and 40 °C.