사막이리응애(Neoseiulus californicus)는 칠레이리응애에 비하여 고온건조한 조건에서 유리하고 점박이응 애, 차응애, 차먼지응애 등 응애류 뿐만 아니라 가루이, 총채벌레 등 다양한 미소해충을 포식 포식하는 광식성 천적으로서 전세계적으로 산업화되고 있다. 사막이리응애를 농가수준에서 증식하기 위하여 간단한 대량생산 방법을 개발하였다. 천적의 먹이원인 가는다리고기진드기와 배지로서 밀기울(70%) 및 팽창질석(30%)을 멸균 팩에 넣고 사막이리응애를 사육하였다. 그 결과 사막이리응애의 밀도는 3주차에 18배로 증식되었다. 증식된 사막이리응애를 딸기 농장에 2월초부터 4월초까지 8주간 매주 투여한 결과 잎당 점박이응애의 밀도는 무처리구 에서 41.5마리이고 천적처리구는 7.0마리로서 점박이응애 방제효과가 83%로 나타났다. 본 연구를 통하여 자가 생산한 사막이리응애를 활용하여 딸기농가의 점박이응애 방제에 효과적으로 사용할 수 있을 것으로 판단된다.

천적의 성공적인 정착과 산란력은 천적의 능력을 판단하는 중요한 기준이 다. 점박이응애를 방제하기 위해 사막이리응애를 사용함에 있어 천적과 해충사이의 적절한 밀도관리를 통한 해충 발생억제기작이 장기간 유지되는 것이 이상적이라 할 수 있다. 본 연구에서는 실험실에서 강낭콩과 장미, 딸기를 기주로 하여 IOBC quality control guideline에 따라 산란력 및 생존율을 조사하여 점박이응애의 생물적 방제인자로서 사막이리응애의 적용 가능성을 확인하고자 하였다. 온도 20, 25, 30℃, 상대습도 70%RH, 광조건 16L:8D에서 각 작물별 산란력을 조사한 결과, 사막이리응애는 20℃에서 산란수는 적고 생존율은 높았으며, 30℃에서 산란수는 증가고 생존율이 급속히 감소하여 산란력과 생존율 간에 반비례의 관계를 보였다. 작물별로는 온도에 관계없이 장미에서 산란수 및 생존율이 높았으며, 강낭콩과 딸기에서의 산란수 및 생존율은 비슷하였다. 따라서 연중 20~28℃의 온도 조건에서 재배되는 장미에 사막이리응애를 사용했을 때 좋은 방제효과를 얻을 수 있을 것으로 기대되며, 딸기의 경우에도 주간 17~20℃, 야간 10℃ 내외로 서늘하여 사막이리응애의 방사밀도를 조절하면 높은 방제 효과를 기대할 수 있을 것으로 생각된다.

Strawberry, Fragaria ananassa Duchesne, is one of the important horticultural crops cultivated in greenhouses. Tetranychus urticae is one of major strawberry pests, and Neoseiulus californicus and Phytoseiulus persimilis have been used as biological control agents for control of T. urticae. The interactions between T. urticae and N. californicus and between T. urticae and P. persimilis were investigated to compare their control efficiency for T. urticae on a spatially-structured strawberry leaf disc area at different temperatures and on different treatments. The experimental arena was an array of leaf discs (3 cm diameter) placed upside down on a water-saturated cotton pad in an aluminum pan (17.4 x 21.5 cm). Twenty leaf discs (4 x 5) were placed adjacent each other for allowing dispersal of T. urticae and its predatory mites. The temperature conditions were 20, 25, and 30°C and there were six different treatments. The overall population densities of T. urticae were influenced by temperature (20, 25, and 30°C) in N. californicus treatment. In the same temperature condition, P.persimilis was more effective than N. californicus to control T. uritcae. Two predator systems were better than one predator systems to suppress the population density of T. urticae at 25°C. Some results of this study could be used to understand the spatial association of T. urticae and its predatory mites in greenhouse crops and fields.

The toxicity of 10 plant essential oils to adults of acaricide-susceptible, chlorfenapyr-resistant (CRT-53), fenpropathrin-resistant (FRT-53), pyridaben-resistant (PRT-53), and abamectin-resistant (ART-53) strains of Tetranychus urticae Koch and to female Neoseiulus californicus McGregor was examined using spray or vapor-phase mortality bioassays. In bioassay with the susceptible adults, strong toxicity was produced by lemon eucalyptus, peppermint, citronella Java, thyme red, caraway seed, pennyroyal, and clove leaf essential oils (LC50, 0.0193-0.0327 mg/cm3). The toxicity of these essential oils was almost identical against adults from either of the susceptible and resistant strains, even though CRT-53, FRT-53, PRT-53, and ART-53 adults exhibited high levels of resistance to chlorfenapyr [resistanc ratio (RR), >9140], fenpropathrin (RR, 94), pyridaben (RR, >390), and abamectin (RR,85), respectively. Against female N. californicus was 1.0 to 1.9 times more tolerant than T. urticae to the test essential oils. Thus, these essential oils merit further study as potential acaricides for the control of acaricide-resistant T. urticae populations as fumigants because of their lower toxicity to N. californicus.

This study was conducted to compare the effectiveness of single and combination use of N. californicus and N. womersleyi for control of Tetranychus urticae. The experiment was conducted with 5 replications in kidney bean leaf disc (2.5cm diameter) at 25℃, 60-70% RH, a photoperiod of 16:8 (L:D) h. The inoculation ratio was 5:1 for T. urticae:pytoseiidae mite and treatments are: a, N. californicus:T. urticae (4 adult female:20 adult female) b, N. womersleyi:T. urticae (4:20) c, (N. californicus+N. womersleyi):T. urticae ((2+2):20) d, Only T. ulticae (20). T. urticae population became significantly lower in the treatment plots than in the control plot but the higher egg number of T. urticae was observed in the treatment "b" plot than in "a" and "c" plots. In the "c" plot, lower number of N. womersleyi was observed than N. californicus. The result indicates that single use of N. californicus and combination use of N. californicus and N. womersleyi were more effective than single use of N. womersleyi but, there was no significantly difference between single use of N. californicus and combination use of N. californicus and N. womersleyi for control of T. urticae. Also, N. californicus appears to interfere or outcompete N. womersleyi.

The objective of this study was to evaluate the effective inoculation position of Neoseiulus californicus for control of Tetranychus urticae on apple branch. This study was conducted under green house conditions. N. californicus was inoculated at different position (Top, Middle and Bottom) of apple branch with a 20:1 ratio (T. urticae:N. californicus). Overall, N. californicus significantly reduced T. urticae numbers in the treatment branches than in the control branch. At 10th day, the T. urticae population was most significantly reduced in the treatment ‘Top’ in which N. californicus were inoculated on the leaf positioned in the top of a branch than in other treatments. At 20th day, most of T. urticae were exterminated in all treatment branches. The daily movement of N. californicus and T. urticae,and their coexistence on apple branch was monitored. Adult N. californicus disappeared from the branch as soon as T. urticae were exterminated in the treatment branches. The result indicates that N. californicus disperse downwards more than upwards in the tree, and the most effective inoculation position for N. californicus for control of T. urticae is the leaves positioned in the top of a branch.

The study was conducted to explore whether environmental differences, in this case the physical characteristics of abaxial leaf surfaces of strawberry cultivars ('Maehyang' and 'Sulhyang' cultivars), affect the functional response of adult female N. californicus preying on immature stages (egg, larva and nymph) of T. urticae. We also evaluated the functional response of N. californicus to eggs of T. urticae at different temperatures (15, 20, 25, 30 and 35℃). We conducted a logistic regression of the proportion of prey consumed as a function of initial prey density to identify functional response types, and used nonlinear squares regression and the random predator equation to estimate attack rates and handling times. The functional response of adult female N. californicus to T. urticae was not influenced by non-glandular trichomes and epicuticular waxes on the abaxial leaf but was affected by temperature. Overall, the functional response of adult female N. californicus exhibited a type 2 functional response to T.urticae. The handling time of N. californicus was highest (1.9970) against T. urticae nymphs. The attack rate did not change much at 15-30℃, but the handling time decreased linearly with increasing temperature. At 35℃, the attack rate was highest (0.1876) and the handling time was lowest (0.9296). The results of this study may be used to evaluate the potential of N. californicus to suppress T. urticae and to estimate parameters for relevant prey-predator models.

Effects of starving treatment on the gravid females of N. californicus were investigated at 20°C and 85% RH. When the females were reared without prey and water just after they laid the first egg under the abundant prey condition, they laid 1.8 eggs and survived for 4.3 d. In order to investigate the process of oogenesis in the body of the starved females, females just after laying the first egg were reared for 0, 12, 24, 36, 48, 72, and 96 hr without prey and water, and were then prepared for internal observation. In the body of females of 0hrstarvation, an egg with eggshell and two oocytes were observed in the ventral and dorsal regions, respectively. Larger oocyte had 2 roundish nuclei and abundant yolk granules, and was enveloped with vitelline membrane. These 2 nuclei were not fused but were just conjugated. Smaller oocyte had a nucleus, but did not form yolk granules and vitelline membrane. Females of 12hrstarvation had an egg in the ventral region and an oocyte in the dorsal region of the body. Females of 24hr-starvation maintained an oocyte in the dorsal region of the body, but did not have an egg in the ventral region. The oocyte was filled with abundant yolk granules, and held 2 irregular-shaped nuclei. Females starved more than 36hr also maintained only an oocyte in the dorsal region of the body. Only an irregular-shaped nucleus was observed in the oocyte. These micrographs suggested that (1) gravid females maintained an oocyte in the dorsal region after laying 2 eggs during starving treatment, (2) the oocyte was not absorbed during starvation, (3) the oocyte advanced vitellogenesis and the fusion of 2 nuclei, and (4) the oocyte was not enveloped with eggshell and did not start embryogenesis. It is also assumed that the sperm penetrated into the oocyte without yolk granules, although the penetration was not observed in this study.

Temperature is an important inorganic factor which affects on every aspect in life of phytoseiid mites in general including N. californicus in this study. Cumulative and short-term effects of temperature through different life stages (immature, mating and oviposition periods) on mating duration and total fecundity of N. californicus were investigated at temperatures of 18, 25, 30 and 350C with a photoperiod of 16L:8D. Throughout experiments, females mated once and egg production was observed until they stop oviposition.

The two-spotted spider mite, Tetranychus urticae Koch, is one of major pests in greenhouse strawberry. Two predator mites, Neoseiulus californicus (McGregor) and Phytoseiulus persimilis (Athias-Henriot), have been widely used for control of T. urticae because they have good functional and numerical responses and searching behaviors. The study of single species releasing and combined releasing of two predatory mites, N. californicus and P. persimilis, was conducted on connected strawberry leaves. The experiments were run under laboratory conditions, 24±1oC, 50-65% RH, and a photoperiod of 16:8 (L:D) h. The excised leaf disk (diameter 3cm) of two strawberry varieties – Maehyang, Sulhyang– were placed upside down on a water-saturated cotton pad in an aluminum pan (width × length 17.4 × 21.5 cm). Twenty leaf disks were placed on each experimental set and the disks (width × length 4×5 cm.) were connected with each other for dispersing of T. urticae and its predatory mite. There were four different experiments – two strawberry varieties and two treatments (releasing single predatory mite, releasing two predator mites). The experiment sets were covered with plastic cage to protect from invading other insects and mites. All life stages of T. urticae and predatory mites were recorded until all mites were vanished. The data were transformed by ln (x+1). Repeated-measures analysis of variance was used to compare the temporal variation in the overall T. urticae and predatory mite density. The average number of T. urticae per leaf arena was significantly different among treatments in Sulhyang (Treatment, df=3, 196, F=17.86, P=0.0001; Time, df=6, 1176, F=47.76, P=0.0001; Time ×Treatment, df=18, 1176, F=22.06, P=0.0001) and in Maehyang (Treatment, df=3, 196, F=42.07, P=0.0001; Time, df=6, 1176, F=64.51, P=0.0001; Time x Treatment, df=18, 1176, F=24.19, P=0.0001). When N. californicus was introduced to P. persimilis system with diminishing prey, P. persimilis population increased more rapidly than N. alifornicus but P. persimilis was displaced by N. californicus. In single or combined releasing system, N. californicus persisted longer after prey depletion than P. persimilis. We examined population growth of P. persimilis and N. californicus in single and combined predatory mite released system with diminishing prey.

Environmental tolerance of three important spider mite predators; Neoseiulus womersleyi, Neoseiulus californicus and Phytoseiulus persimilis (Phytoseiidae) was experimented by treating combination of temperature and relative humidity for egg hatching and immature survival. Egg hatching rate increased at the relative humidity incrased for three species. Temperature effects were only significant to N. californicus and P. persimilis. The lethal humidities for three species were in the range of 56-77, 82.0, 66-94% RH, respectively. Larva does not need to feed for larval development into protonymph in three tested species. No larvae survived at lower than 75% RH for N. womersleyi, but around 80% at 95% RH. N. californicus larvae survived around 50% and 100% at 75 and 95% RH. P. persimilis larve survival was decreased as the temperature increased at 75% RH, but platued around 100% at 95% RH. Cannibalism was higher in N. californicus and lower in P. persimilis. Implementation of the results was discussed relative to biological control of spider mites in open field and greenhouse crops.

A phytoseiid mite, Neoseiulus californicus was newly found from Jeju citrus orchards in Korea and it is a polyphagous predator of mite and small insect pests as well as plant pollens. Recently in Korean apple orchards, Tetranychus urticae and Panonychus ulmi are imposing similar pest pressure. Even with ample information of this predator interacting with T. urticae, little is known on the interaction with P. ulmi. We investigated temperature effects on life history parameters of N. californicus when feeding on P. ulmi as prey in the laboratory condition to check the possibility to use this predatory mite in apple mite biological control. So, the development, survivorship and life-table parameters of the predator were studied by given mixed stages of P. ulmi as prey under the range of temperatures (15-34°C), RH 75±10%, and photoperiod 16L:8D to determine the effects of temperature. Temperature had a significant effect on mean development time from hatching to adult emergence and other life-history parameters. The results specified that the developmental time is decreased with increasing temperature between 15 and 30oC. Female development times were shorter at 25, 30 and 34°C (3.83±0.07, 3.37±0.24 and 3.53±0.11d, respectively) and were longest at 15°C (15.61±0.22d). Male developmental times were shorter than females ones at each temperature. The highest adult female life span (70.42±3.06d) and oviposition period (35.83±1.43d) observed at 15oC whereas the shortest at 34oC (13.06±1.03 and 7.3±0.94d, respectively). At 25oC, females laid maximum number of eggs (63.94±2) while minimum (16.59±0.98) was at 34oC. In sex ratio, utmost number of females (0.77±0.01) was counted at 25oC and lowest (0.67±0.01) at 34oC. Survivorship during immature development varied from 78.78 to 93.75% with the lowest value recorded at 20 and 34oC. From life table analysis, the shortest generation time (T=10.7d) resulted at 34oC. The highest net reproductive rate (R0=44.31; expected progeny per female) was found at 25oC. The intrinsic rate of natural increase (rm=0.29) and the finite rate of increase (λ=1.33) per day was estimated highest at 30oC. From this study, we found that N. californicus could successfully develop and oviposit vital eggs. Based on these results, we cautiously expect that N. californicus could be used as a biocontrol agent of spider mites in apple orchards when P. ulmi or T. urticae occurs singly or mutually.

Neoseiulus californicus (McGregor) is a potential biological control agent of spider mites in orchards. The field occurrence of this species was first reported from citrus orchards in Jeju Island and recently this mite started to be sold as a commercial product in Korea. However, the natural occurrence of N. californicus in the Korean mainland is unclear or quite limited. At this time, it is not certain whether N. californicus can overwinter in the Korean mainland or not. This mite is presently planning to be used as a biological control agent against spider mites in apple orchards of the Korean mainland. The main objective of this study was to investigate natural overwintering sites of N. californicus and possible factor increasing winter survival of this species, to develop effective method for collecting overwintering population of N. californicus. For the first objective, we conducted field survey in two citrus orchards of Jeju in early and late February 2008. Samples were collected from various possible overwintering sites: citrus trees, ground covers and windbreaks. Total 259 phytoseiid mites were collected, 94% of the mites were identified as N. californicus and 98% of them were adult females. Most of N. californicus were collected from ground covers, specially the weed species which had rosette leaves: Youngia japonica (L.) DC. and Erigeron spp. This result seemed to suggest that N. californicus try to hide beneath weed leaves near ground surface during winter to get successful survival. Thus, the second experiments were conducted in Andong from December 2007 to early March 2008. N. californicus conditioned in a greenhouse with natural day length was individually put in a small tube, and the tubes were kept under different ground surface conditions: bare, fallen leaves and urethane foam. When water had been added in the tube, the mites on bare ground had died after one month, while 70% of the mites of the other cover treatments were surviving. In these cover treatments, 7-10% of the mites had survived until two months, and eventually all died within three months. This result showed that hiding under cover structure near ground surface may be effective to increase winter survival of N. californicus. Therefore, collecting weeds which have rosette leaves may be an effective method to estimate of the overwintering possibility of N. californicus in the Korean mainland.

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.

The developmental time and survival of immature stages of N. californicus were studied under laboratory conditions at nine constant temperatures (12, 16, 20, 24, 28, 32, 36, 38, 40℃), 60-70% RH, and a photoperiod of 16:8 (L:D) h. The total developmental period decreased with increasing temperature between 12 and 32℃, and increased beyond 32℃. Total developmental period of immature stages was longest at 12℃ (18.38 days) and shortest at 32℃ (2.98 days). The cumulative mortality of N. californicus was lowest at 24℃ (4.5%) and highest at 38℃ (15.2%). The normalized cumulative frequency distribution of developmental times for each life stage was fitted to the three-parameter Weibull function (r2=0.91~0.93). The relationship between temperature and developmental rate was fitted by five nonlinear development rate models (Logan 6, Lactin 1, 2, and Briere 1,2). The nonlinear shape of temperature development was best described by the Lactin 1 model (r2=0.98). The determined lower developmental temperature thresholds could be used to predict the occurrence, number of generation and population dynamics of N.californicus on fruit orchards and greenhouse

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.

Temperature and humidity are the vital environmental factors influencing the distribution and abundance of ectothermal organisms. Also, these variables often determine the efficacy of biological control of spider mites using phytoseiid mites N. californicus, N. womersleyi and P. persimilis are promising biocontrol agents of spider mites. The combined effects of temperatures (15,20,25,30 & 35oC) and relative humidity (33,51,75 & 95%) on egg hatch, incubation period from single egg and cannibalism from five eggs experiment were tested for three phytoseiid mites. Photoperiod was set to 16L:8D and neither water nor diet was provided. The result showed that higher temperatures (30&35oC) and lower relative humidity (33&51%) caused increased egg mortality by shrinking and desiccation. The egg hatch of N. californicus and P. persimilis were higher than N. womersleyi in all conditions with the exception of 35oC and 95% RH treatment where P. persimilis did not hatch at all. The incubation periods of egg decreased as the humidity level increased even under the same temperature. The cannibalism, habit of feeding the same species was found from protonymphal and deutonymphal stages under higher humidity levels (75&95%) in the three phytoseiid species. This tendency was higher in N. californicus and N. womersleyi than in P. persimilis. The results partially explain the lower predator performance during hot summer by P. persimilis and the possibility to sustain the predator population when the prey population is low.

날개가 없는 몇몇 절지동물들은 공중이동을 하기 위한 수단으로써 이륙행동 보이는 종들이 있다. 본고는 포식성 이리응애류중에서 이륙행동을 보이는 종(Neoseiulus fallacis (Carman)) 과 이륙행동은 보이지 않으나, 공중이동률이 높은 종(Phytoseiulus persimilis Athias-Henriot),이륙행동이 없고 공중이동률이 중간치인 종(N. ca1ifornicus(McGregor))간에 공기역학적 측면에서 어떠한 메커니즘이 작용하는 지에 관한 연구이다. 위 종들의 도보이동 자세와 공주 이동 이륙행동 자세의 몸체의 수직적 위치, 몸체의 크기, 다리의 길이 등의 자료를 가지고 공기역학적 파라미터를 계산한 결과, P. persimilis는 도보이동 자세에서도 N. fallacis가 이륙행동을 보여야만 얻을 수 있는 양의 항력을 얻을 수 있음이 밝혀졌다. 이러한 관점에서 포식성 이리응애류의 이륙행동 진화에 대한 고찰하였다.