The Accumulated Heat Units Required for the Development of the Different Stages of the Grape False Spider Mite, Tenuipalpus granati Sayed Under Laboratory Conditions

Al-Sweedi, T.M.M. 2022. The Accumulated Heat Units Required for the Development of the Different Stages of the Grape False Spider Mite, Tenuipalpus granati Sayed Under Laboratory Conditions. Arab Journal of Plant Protection, 40(4): 351-355. https://doi.org/10.22268/AJPP-40.4.351355 The grape false spider mite Tenuipalpus granati Sayed (Acariformes: Tenuipalpidae) is one of the significant pests on the grape trees in Iraq. The aim of this study was to determine the threshold temperature and calculate the heat units needed for the development time of the duration of this mite stage. Different incubation temperatures (10 15, 20, 25, 30, 35, and 40±2°C), relative humidity (50-60±5%), and light:darkness period of 16: 8 hours were applied to rear this mite on the lower surface of the newly grown grape leaves. The results showed that the development time of the egg, larva, protonymph, and deutonymph (active, quiescent, active + quiescent) at temperatures 15, 20, 25, 30, and 35°C were decreased gradually with temperature increase. Furthermore, the development time of the eggs incubation period was 15.3, 4.98 days and the larva (active + quiescent) were 15.1, 4.43 days, and the protonymph (active + quiescent) was 14.4, 3.48 days and of the deutonymph (active + quiescent) was 15.6, 5.58 days for the effect of 15 and 35°C. Additionally, the development time from egg to adult was 60.00 and 18.26 days at 15 and 35°C, respectively. The threshold temperature was 6.73, 7.89, 9.38, 6.47 and 7.3 °C, respectively. Finally, the accumulated heat units required for the development time of each mite instar varied according to the threshold temperature difference and development time. Keywords: False red mite, heat units, Tenuipalpus granai, developmental rate.