In Jeju cirtrus orchards, Panonychus citri, citrus red mite is the most important pest requiring 3 times acaricide sprays. In open field conventional orchards, P. citri usually shows three population peaks; from end of Jun to July, from end of Aug. to Sep., from end of Oct. to Nov. However, natural enemy complex and its function regulating P.citri are poorly understood. From the survey of P.citri natural enemy in citrus orchard in Jeju from 2004 to 2006, predatory beetle, Oligota spp. was most abundant. Three predatory mite, N. californicus, Amblyseius eharai, and N. barkeri, were identified. Among them, the predatory mite, Neoseiulus californicus (McGregor) (Acari: Phytoseiidae), was first found in Korea. Even though it was first found, N. californicus was the dominant species occupying 84% of phytoseiid mites. These predatory mites mostly occurred in Jun and peaked at July, which was accorded with the high humidity season of the year. From the survey, the density relationship with P. citri was unclear. From the study conducted in 2005-2007, N. californicus was more abundant in greenhouse citrus (var. Shirahuhi) than in open field orchards; conventional or organic mandarine citrus. In greenhouse citrus, phytoseiid mites showed suppressing P. citri population. As a next step, the inundative biological control study was conducted using commercial strain of N. californicus, which was originated from Jeju, 2005, in greenhouse citrus. One thousand N. californicus per 1a were released 2 times at 10 day interval on citrus leaves when the initial density of P. citri was about 0.2 per leaf. The release effects were variable depending on the field condition. However, N. californicus did successfully reduce P. citri in greenhouse citrus orchards.

As suggested by Kawashima (2006), the most abundant Tetranychidae was Tetranychus sp. as a pest in persimmon orchards. The observatory orchards were selected 16 in total, 2 from Gurye, 2 from Gwangyang, and 2 from Suncheon in Jeonnam Province and 3 from Jinju, 4 from Sacheon, and 3 from Sancheong in Gyeongnam Province. Number of mites in 100 persimmon leaves were observed from each orchards nearly every ten days. Careful rearing of the mites sample collected from the four observaory persimmon fields at which the mite had occurred the most seriously among 16 fields and results from taxanomical identification process indicated that the species was identified Tetranychus urticae. Maximum number of T. urticae reached to 436 on 27 June at Jeongdong, Sacheon, 108 on 1 August at Sinann, Sancheong, 406 on 26 June Okgok, Gwangyang, and 509 on 15 June Muncheok, Gurye. When the number reached to more than 400 mites, the persimmon leaves changed from clear yellow dots, to pale yellow, and to grey in the backside. An experiment was conducted to control T. urticae and to select highly active miticide in persimmon orchards in Jinju and Sacheon. Spiromesifen 20SC and acequinosyl 15 SC were effective.

Neoseiulus californicus (McGregor), which is a potential biological control agent of spider mites, has been produced by some Korean natural enemy companies. Now, our project related to the biological control of spider mites by releasing N. californicus in apple orchards is going on. The field occurrence of this species in Korea was first reported in Jeju citrus orchards (Jung et al. 2006). However, the natural occurrence of the mite has not been recorded in Korean mainland so far. Therefore, it is questioned whether the released N. californicus population originated in Jeju can successfully overwinter in Korean mainland. First, to clarify the natural overwintering sites in field, we conducted field samplings in Jeju citrus orchards in Feb. 2008. Samples were collected from the various possible overwintering habitats, such as citrus leaves and twigs, ground covers and windbreaks. Most of the mites were collected from ground cover samples. Next, to estimate of the winter mortality, the mite was individually put in small tubes which have some different food conditions, and the tubes were kept under the different ground surface conditions in the university experimental orchard in Dec. 2007. Most of the mites had died by late Jan. and all by early Mar. 2008. And also, to evaluate the field survival of the mite, in the spring 2008, sampling would be conducted in apple orchards in Cheongsong where we released the mites in 2007. From these data, we would discuss possible overwintering of N. californicus in Korea.