Ecological characteristics of the perilla rust mite, Shevtchenkella sp., a serious pest species of Perilla frutescens

Ecological characteristics of the perilla rust mite, Shevtchenkella sp., that causes damage to Perilla frutescens (Lamiaceae) were studied under a range of temperatures. The mean generation times were 27.3, 15.4, 11.3, 8.8, and 7.8 days at 18, 21, 24, 27, and 30°C, respectively. The estimated lower thermal threshold was 12.8°C, and the thermal constant for egg-to-egg development was 133.5 degree-days. The intrinsic rate of natural increase (rm) was 0.1001, 0.1504, 0.2020, and 0.2146 at 21, 24, 27, and 30°C, respectively. The rm value was not calculated at 18°C as more than 70% of the mites failed to reach adulthood, and of those that did, only 2.6% laid eggs. Zero fecundity was estimated at 12.8°C based on regression analysis performed using the average number of eggs per female per day. Most females reared with a 13 h photoperiod at 21°Cin the laboratory were in diapause. The population of the perilla rust mite used in these tests in the laboratory was collected from Kochi Prefecture, Japan.Fifty percent of the diapause females of the perilla rust mite collected from the field in Tokyo in 2015 were forecasted to appear in early October. The nymphs and adults were trapped outside two greenhouses on glass slides coated with high-vacuum silicone grease in Kochi Prefecture throughout the year, indicating that perilla rust mites disperse through air.