BIOLOGICAL CHARACTERS OF KOREAN NEOSEIULUS CALIFORNICUS MCGREGOR (ACARI: PHYTOSEITDAE) IN RELATION TO ENVIRONMENTAL PARAMETERS

Abstract

Spider mite is one of the most important pests of apple in Korea. Two spotted spider mite and European red mite are the most common in apple and they are in competition. Recently European red mite is becoming dominant over two spotted spider mite in Korean apple orchards. As the acaricide application has been the most option employed to control spider mites and as wide range of acaricide resistances have been the concerns, alternative control options are in demand. Biological control of spider mites by predatory mites has been tried on a wide range of crops including apples. This study examined the feasibility of using a Korean isolate Neoseiulus californicus (Acari: Phytoseiidae) as a potential biological control agent in apple orchards in the mainland Korea. The distribution of this naturally occurring predatory mite is restricted only to the southern, warmer island, Jeju but not in the relatively cooler main domain of Korea. Scanty of information is available on the biological characters and overwintering phenology of this native predator. Temperature effect on life history parameters of N. californicus using Panonychus ulmi was experimented to evaluate the suitability of this predatory mite for controlling apple mites. The results specified that the developmental time is decreased with increasing temperature between 15 and 30°C. At 25°C, females laid maximum number of eggs. The highest net reproductive rate (Ry = 49.24) and the intrinsic rate of natural increase (r,, = 0.29) were found at 25 and 30°C, respectively. Environmental 126 tolerance of Neoseiulus californicus was compared to the native dominant phytoseiid, Neoseiulus womersleyi and the introduced, most widely used phytoseiid, Phytoseiulus persimilis (Phytoseiidae) by treating combination of temperatures and relative humidity for egg hatching, immature survival, and adult female performance. Korean N. californicus was most tolerant to high temperature and low humidity, N. womersleyi was more humid susceptible and P. persimilis showed high temperature susceptible with high reproductive ability. While food limited, cannibalism was higher in N. californicus and they may get benefit for their survival. Overwintering phenology was studied with a view to establish this predator in the lion cooler part of Korea. As a part of overwintering phenomena, diapause propensity of the native predator was measured and diapause induction was not found in N. californicus isolated from Korea. Cold tolerance of the Korean WN. californicus was also measured as the non-diapausing population can survive up to certain limit of cold temperatures for a certain period. The survivorship of this predator at all subzero temperatures could assume the possibility to establish in the main domain.