Abstract
The spider mite, Eotetranychus smithi Pritchard & Baker (Acari: Tetranychidae), exhibits a facultative diapause that occurs at the egg stage. Diapause was induced by low temperatures alone (≤ 17.5°C) and averted by high temperatures (≥ 20°C). Photoperiod had little effect on diapause induction. This is the first example of temperature-induced diapause in spider mites. The diapause eggs became larger and darker (orange) than non- diapause eggs (white to pale yellow), suggesting that egg size and egg color are associated with diapause. When mites that were reared from eggs at 25°C and 16:8 L:D were transferred to 15°C and 16:8 L:D just after the start of the teleiochrysalis stage (the final molting stage before adulthood), all females laid non-diapause eggs during the first 30 days and then switched over to laying diapause eggs. The switch to diapause may be caused by the aging of mothers.
Highlights
Many arthropods enter diapause to synchronize their activities to favorable times and to enhance their survival during unfavorable periods in the year (Friedrich 1984; Tauber et al 1986; Danks 1987, 2007; Friberg et al 2011)
Eotetranychus smithi is a potential pest of grape and strawberry in Japan, and sometimes outbreaks occur in greenhouse cultivated crops (Itagaki 1998; Ehara and Gotoh 2009)
As 2–5 unhatched eggs, shown in parentheses, were observed at 20 and 25°C, they were discarded from the calculation of egg duration. bData analyzed using analysis of variance (ANOVA); ***: P < 0.001
Summary
Many arthropods enter diapause to synchronize their activities to favorable times and to enhance their survival during unfavorable periods in the year (Friedrich 1984; Tauber et al 1986; Danks 1987, 2007; Friberg et al 2011). Photoperiods mainly regulate the timing of the onset of diapause, and temperatures can have a secondary effect by enhancing or inhibiting the induction of diapause by photoperiod (Claret and Carton 1980; Tauber et al 1986; Danks 1987). The E. smithi Akitsu strain enters facultative diapause in the embryonic stage under 20°C/12 hr light and 10°C/12 hr dark conditions
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