Seasonal changes in the deleterious effects of solar ultraviolet-B radiation on eggs of the twospotted spider mite, Tetranychus urticae (Acari: Tetranychidae)
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Solar ultraviolet-B (UVB) radiation has deleterious effects on plant-dwelling mites. We assessed the biological effects of UVB radiation on the eggs of the twospotted spider mite, Tetranychus urticae Koch, under both near ambient (UV+) and UV-attenuated (UV−) conditions from spring to autumn and compared them to the effects of temperature and humidity. The ambient daily UVB irradiance increased from January to August and then decreased rapidly until December, whereas egg hatchability under UV+ was lowest in April (10.7%) and increased almost linearly until October (74.9–92.3%). In contrast, hatchability under UV− was consistently high (96.2–99.8%) through all seasons. For UV+, the stepwise multiple linear regression analysis supported the negative correlation of hatchability with cumulative UVB irradiance during egg periods (cumulative dose), but did not support that with the mean daily UVB irradiance (dose rate), suggesting that UVB-induced mortality in T. urticae eggs is cumulative dose dependent rather than dose rate dependent. The high mortality in April may have reflected the slower development caused by the relatively lower temperature and higher UVB radiation, increasing the cumulative dose, while the low mortality in October may have reflected the faster development caused by the relatively higher temperature and lower UVB radiation, decreasing the cumulative dose.
KeywordsMite community Habitat determination UV damage Ambient UVB toxicity
This study was supported by a Grant-in-Aid for Scientific Research from the Ministry of Education, Culture, Sports, Science, and Technology of Japan (18580053).
- Ferro DN, Chapman RB (1979) Effects of different constant humidities and temperatures on twospotted spider mite egg hatch. Environ Entomol 8:701–705Google Scholar
- Jones VP, Parrella MP (1984) Intratree regression sampling plans for the citrus red mite (Acari: Tetranychidae) on lemons in southern California. J Econ Entomol 77:810–813Google Scholar
- Perring TM, Holtzer TO, Toole JL, Norman JM, Myers GL (1984) Influences of temperature and humidity on pre-adult development of the banks grass mite (Acari: Tetranychidae). Environ Entomol 13:338–343Google Scholar
- Shih CT, Poe SL, Cromroy HL (1976) Biology, life table, and intrinsic rate of increase of Tetranychus urticae. Ann Entomol Soc Am 69:362–364Google Scholar