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.