Dispersal of Tetranychus urticae and its predatory mite on connected strawberry leaves

JeongJoon Ahn,Joon-Ho Lee 한국응용곤충학회 2008 한국응용곤충학회 학술대회논문집 Vol.2008 No.05

The study was conducted to investigate dispersal of T.urticae and its predatory mite on connected strawberry leaves. The experiments were run on laboratory conditions, 24±1℃, 50-65% RH, and a photoperiod of 16:8 (L:D). The excised leaf disk (diameter 3cm) of two strawberry varieties- Maehyang, Seolhyang- were placed upside down on a water-saturated cotton pad in an aluminum pan (width x length 17.4 x 21.5cm). Twenty leaf disks were placed on each experimental set and the disks (width x length 4 x 5 ca) were connected with each other for dispersing of T. urticae and its predatory mite. There were six different experiment sets - two strawberry varieties and three treatments (no predatory mite, releasing Neoseiulus californicus, and releasing Phytoseiulus persimilis). The experiment sets were covered with plastic cage to protect from invading other insects and mites. The investigation was conducted by examining two or three times per week and all life stages of T. urticae and predatory mite were reported until all leaves were occupied by mites. Repeated-measures data were analyzed by MANOVA. The average number of T.urticae per cm2 was no significant difference between two strawberry varieties in no predatory mite system (F=0.65, p>0.4195). Although the external structure of two strawberry varieties is very similar the dispersal rate of T. urticae was different between two strawberry varieties in all experiment sets. However, the number of T. urticae per cm2 was no significant different (df=1, F=1.28, p>0.2628). Within the same strawberry variety T.urticae populations among experiment sets were significant different (df=2, F=14.95, p<0.0001 Seolhyang, df=2, F=15.03, p<0.0001 Maehyang).

Population dynamics of Tetranychus urticae and its predatory mites, Neoseiulus californicus and Phytoseiulus persimilis, on connected strawberry leaf arena

JeongJoon Ahn,Joon-Ho Lee 한국응용곤충학회 2008 한국응용곤충학회 학술대회논문집 Vol.2008 No.10

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.

Spring emergence pattern and its forecasting of Grapholita molesta (Busck) (Lepidoptera: Tortricidae) in stone fruit orchards

JeongJoon Ahn,Jiwon Kim,Soon Won Lee,Chuleui Jung 한국응용곤충학회 2011 한국응용곤충학회 학술대회논문집 Vol.2011 No.05

The study was conducted to investigate the spring emergence pattern of G. molesta and to forecast the emerging time of overwintering G. molesta on tree fruit orchards. G. molesta is one of major insect pests on fruit trees in Korea. The host range of G. molesta includes many economically important tree fruit plants such as apple, pear, peach and plum. The overwintering G. molesta emerge from late March as an adult lay eggs on the shoot of peach or fruits of apple, plum and peach. Therefore, it is important to understand the biofix and to forecast the emerging peak period of overwintering G. molesta for establishing the pest management strategy. The pheromone trap of G. molesta has been utilized to monitor the population density in apple orchard. The commercial stick trap (GreenAgroTech) and lure (Z8-12:AC, E8-12:Ac, Z8-12:OH, 95:5:1) was set to monitor the population density of G. molesta on each place (56 different fruit orchards). The record of temperature was received from meteorological center close to monitoring orchards. The parameters for forecasting the emerging time and peak period of overwintering G. molesta were calculated from the results of Yang et al (1997 and 2001). Although the estimated biofix of G. molesta was not fitted well, the peak period of overwintering G. molesta was explained by linear regression model. The spring emergence pattern of G. molesta was presented differently related to host plant and geographical location. The peak period of G. molesta at the same mornitoring county was presented differently according to host plant. The synchronization between host plant and G. molesta may be studied to figure out the spring emerging time of overwintering G. molesta.

The Phenology and degree-day Model of Grapholita molesta (Tortricidae: Lepidoptera) in Apple Orchards

JeongJoon Ahn,Lalit Prasad Sah,Hyangmi Kim,Soonwon Lee,Chuleui Jung 한국응용곤충학회 2013 한국응용곤충학회 학술대회논문집 Vol.2013 No.04

The study was conducted to investigate the phenology of G. molesta adult, and to develop and validate the degree-day model of G. molesta in apple orchards. It was known that G. molesta is a multi-voltine insect depending on temperature and geographic location. G. molesta damage to many economically important fruit trees such as apple and pear. Data collection was carried out in five apple-growing location (Chungju, Bonghwa, Andong, Uiseong, and Geochang) and at least three commercial orchards of each location was selected for collecting data in 2011 and 2012. The commercial pheromone monitoring trap (GreenAgroTech) was used to investigate the flight phenology of G. molesta. The relationships between degree-day accumulated above the low temperature threshold and cumulative proportion of accumulated G. molesta caught per generation were used to predict the phenology of G. molesta. The phenology of G. molesta per generation was analyzed by Weibull 2-parameter function. The generation of G. molesta was depending on local environmental conditions, specially temperature. The first flight of G. molesta adult in Chungju was later than other places. The average number of G. molesta caught in Uiseong was significanlty decreased from 2011 to 2012. The occurrence of G. molesta adult was explained well by degree-day model using Weibull 2 parameter function. The developed model system could be applied to manage G. molesta population in apple orchards.

Forecasting the phenology of important lepidopterous pests, Grapholita molesta, Grapholita dimorpha and Carposina sasakii: II. Case study of apple

JeongJoon Ahn,Jiwon Kim,Seon Ah Jeong,Lalit Prasad Sah,Chuleui Jung 한국응용곤충학회 2011 한국응용곤충학회 학술대회논문집 Vol.2011 No.10

Grapholita molesta, G. dimorpha and C. sasakii as “internal feeders” are important apple pests in Korea. Three species overwinters around and in apple orchards. New young larvae of three species bore into new shoots or fruits and then feed inside apple. When mature larvae escape from fruits they make holes that reduces the commercial value of fruit. Therefore, understanding the phenological distribution of three species is critical to establish the precise management system for reducing three species population. The study was conducted to investigate the adult emergence of G. molesta, G. dimorpha and C. sasakii using pheromone traps and to forecast the cumulative proportion of each population. This study is second part of consecutive experiment. Data collection was carried out on three commercial apple orchards and one experimental orchard of Giran in 2010 and 2011. The experimental process was same in the study of plum. More than 50% of G. molesta male was occurred in spring season (within 500 degree-days), 2010 and 2011. The adult emergence of G. dimorpha and C. sasakii was linear and sigmoidal pattern in each year. The phenology of C. sasakii was explained well by nonlinear functions and the equation 3, 6, 8 and 11 were selected based on AICc and BIC. The selected equations were validated by the data of present year (2011) in each region. The performance of G. molesta and G. dimorpha was analyzed well by bimodal functions. The importance of phenological model is discussed to develop and maintain a more precise system for multiple pest management on apple orchard.

Spatio-temporal distribution of Grapholita molesta (Busck) (Lepidoptera: Tortricidae) within orchard and among orchards.

JeongJoon Ahn,Yonggyun Kim,Seon Ah Jeong,Lalit Prasad Sah,Chuleui Jung 한국응용곤충학회 2011 한국응용곤충학회 학술대회논문집 Vol.2011 No.10

Understanding the spatial pattern of G. molesta and the temporal variation of their patterns are important to develop and maintain pest management programs in fruit orchards. The overwintering larvae of G. molesta pupate early in the spring and new adults begin a flight for several reasons such as mating, seeking resources (food or shelter) and oviposition. It was known that G. molesta presented “low movement activity” and male G. molesta flight behavior was closely related to the proximity of its host crops. Unmated males remain near the site of emergence in order to find and copulate with unmated females. The fruit-bearing status of orchards are important factors for G. molesta movement. To elucidate the spatial distribution and temporal variation of G. molesta within and among orchards, pheromone traps targeting male G. molesta were used because the trap represent a reliable and economic tool for monitoring adult G. molesta populations. The study was conducted in two apple orchards (one is isolated from other fruit orchards and another is surrounded by apple orchards), Andong and in seven plum orchards, Uiseong, 2010. Using spatial analysis by distance indices, the spatial pattern of G. molesta in each sampling date was presented. In the study of the spatial pattern within apple orchard, the index of aggregation (Ia) of isolated orchard were presented >1, indicating an aggregated distribution pattern, from monitoring results. The spatial association between successive monitoring using X (the index of spatial association) was negative during spring season and after then the value was changed to positive. In the experiment of the spatial pattern among orchards, the index of aggregation was >1 in most monitoring date and the index of spatial association was negative during early and late growing season. Factors influencing the spatial-temporal dynamics of G. molesta are discussed.

Degree-day Model and Phenology of Grapholita mole (Tortricidae: Lepidoptera) in Pear Orchards

JeongJoon Ahn,Lalit Prasad Sah,Hyangmi Kim,Soonwon Lee,Chuleui Jung 한국응용곤충학회 2013 한국응용곤충학회 학술대회논문집 Vol.2013 No.04

Grapholita molesta is one of economically important pests in pear orchards and has four to five generations per year depending on food resources, geographic location, and temperature. The overwintering larvae of G. molesta pupate early in the spring and new adults start to flight for several reasons such as mating, seeking resources and oviposition. The study was conducted to develop the full seasonal phenology model of G. molesta and to investigate the phenology of G. molesta adult in pear orchards. Data collection was carried out in five pear-growing location (Anseong, Icheon, Sangju, Ulju and Naju). Three commercial orchards of each location was selected for collecting data in 2011 and 2012. The flight phenology of G. molesta was investigated by the commercial pheromone monitoring trap (GreenAgroTech) once per week. The phenology of G. molesta per generation was predicted by the relationships between degree-day accumulation above the low temperature threshold and cumulative proportion of accumulated moth caught per generation. The phenology of G. molesta per generation was calculated by Weibull 2-parameter function. Although the latitude of Sangju was higher than that of Naju, the first flight of G. molesta adult from two orchards was similar. The average number of G. molesta adult caught in every pear orchards was increased from 2011 to 2012. The occurrence of G. molesta adult was explained well by degree-day model using Weibull 2-parameter function.

Comparison of Single and Combination use of Neoseiulus californicus and Neoseiulus womersleyi for Control of Tetranychus urticae

TaeGyun Kim,Jeongjoon Ahn,YongJun Kwon,Joon-Ho Lee 한국응용곤충학회 2009 한국응용곤충학회 학술대회논문집 Vol.2009 No.05

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.

Oviposition Behavior of Tetranychus urticae Koch (Acari: Tetranychidae) on Host Plant Leaves with Different Trichome Densities

YongJun Kwon,JeongJoon Ahn,TaeGyun Kim,Joon-Ho Lee 한국응용곤충학회 2009 한국응용곤충학회 학술대회논문집 Vol.2009 No.05

This study was conducted to determine whether trichome density affects the oviposition behavior of adult female Tetranychus urticae Koch on host plant leaves. Experiments were conducted with twenty replications on the leaf discs of each plant (Pear, 'Niitaka'; Apple, 'Fuji'; Strawberry, 'Meahyang'; 3cm diameter) at 25℃, 60-70% RH and a photoperiod of 16:8 (L:D) h. One female T. urticae was placed on each disc. The number and locations of laid eggs were recorded at 24 h intervals until T. urticae died. The trichomes were distributed along the midrib of abaxial surface of pear leaves but were evenly distributed on that of apple and strawberry leaves. Eggs were mostly laid along the midrib of pear leaf disc, but eggs were laid not only along the midrib but also randomly over the leaf disc of apple and strawberry. Therefore, it appeared that T. urticae preferred to lay eggs on the specific location where trichomes were densely distributed. Further study is needed to quantify how different distribution patterns of T. urticae eggs on different plant leaves affect the efficacy of predatory mites to control T. urticae.

Temperature-dependent development model of Neoseiulus californicus (Acari: Phytoseiidae)

TaeGyun Kim,JeongJoon Ahn,Joon-Ho Lee 한국응용곤충학회 2008 한국응용곤충학회 학술대회논문집 Vol.2008 No.05

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