Long-Term Characteristics of Seasonal Development of Spider Mites of the Genus Tetranychus Dufour, 1832 (Acariformes, Tetranychidae) on Strawberry in Moscow Province

摘要

Data on the seasonal development of spider mites in strawberry fields over 13-14 years have been obtained in Moscow Province, Russia. Tetranychus atlanticus McGregor, 1941 was found to be the dominant species, Some fields were also infested by the Sawzdargi spider mite, Tetranychus sawzdargi Mitrofanov, 1980; the two-spotted spider mite, Tetranychus urticae Koch, 1836, was found on commercial strawberry plants only in greenhouses. The observations demonstrated that the reactivation and oviposition ofthe overwintered T, atlanticus females begins at the maximum air temperature of 12 and 14°C. The maximum and the daily mean air temperatures recorded between April 1 and June 10, which is the developmental period of the first generation of spider mite,were used to calculate the low-temperature threshold, estimated by the daily mean temperature. From the data obtained, 9°C appeared to be the most reliable threshold for prediction of development, Peak reactivation of overwintered females in strawberryfields was recorded at 11.8 day-degrees above 9°C in the third decade of April, Peak oviposition was recorded at 16,6 day-degrees. Hatching of the first larvae was observed at 48,0, and peak hatching, at 78.7 day-degrees (on the average), in the firstand second thirds of May, respectively. Approximately 101.4 ± 5,6 and 141.1 ± 5.2 day-degrees accumulated above 9°C were required for the first and peak emergence of the first generation of mites, respectively. The average duration of the developmentof the first generation was 31 days. A strong correlation between the mean temperature and the time of development was found. The thermal constant of spider mites in strawberry fields, determined by numerical and graphical methods, was found to be about160°C. In Moscow Province, spider mites completed 5 (7 at maximum) generations per season, Approximately 802 day-degrees were required for 5, and 962 day-degrees, for 6 generations, The relation between the total day-degrees and the number of generations in spider mites can be described with the formula: y = 159.72x + 3.45. The results obtained can be used in IPM programs for modeling of the population dynamics of spider mites, prognosis of the appearance of certain developmental stages, and calculation of the optimum time of application of acaricide or predatory mites for control of spider mites.