Chuleui Jung

Ambulatory and Aerial Dispersal Among Specialist and Generalist Predatory Mites (Acari: Phytoseiidae)

Abstract Predator-prey systems having a specialist predator often are over-exploitive, unstable and transient while similar systems having a generalist predator show less fluctuation, more stability and regulation of prey at lower densities. These population dynamics also affect dispersal patterns between specialist and generalist predators. In this study, ambulatory and aerial dispersal were assessed for five predaceous phytoseiid mites having different degrees of predation specialization: Phytoseiulus persimilis Athias-Henriot, Specialist I; Neoseiulus fallacis (Garman) Specialist II; N. californicus Chant, Specialist II/Generalist III; Kampimodromus aberrans (Oudemans), Generalist III; and Euseius finlandicus (Oudemans), Generalist IV. In general, specialist species had more walking activity and aerial dispersal than generalist species. Somewhat different dispersal strategies were seen between N. fallacis and N. californicus. Dispersal from a prey (twospotted spider mite, Tetranychus urticae Koch) patch was earlier for the more generalized N. californicus, and N. fallacis (more specialized phytoseiid) remained without dispersing until almost all prey were eliminated. Both dispersed aerially at similar rates. In general, cues from spider mite infestations decreased dispersal of specialist phytoseiids, but either acted to increase or not affect dispersal of generalist feeding phytoseiid species.

Phytoseiid dispersal at plant to regional levels: a review with emphasis on management of Neoseiulus fallacis in diverse agroecosystems

Dispersal behaviors of phytoseiid and tetranychid mites are key factors in understanding predator-prey dynamics and biological control of pest mites at different spatial levels in agricultural and natural ecosystems. In this review, ambulatory and aerial dispersal of both mite groups are discussed at spatial levels of leaf, plant, crop and region. Emphasis is on dispersal of phytoseiids, and specifically, the specialist-predator, Neoseiulus fallacis (Garman), and two-spotted spider mite prey, Tetranychus urticae (Koch). Dispersal aspects that are discussed are ambulation on a leaf; plant or in a prey patch; aerial dispersal between plants; behavior and aerodynamics of aerial take-off; modeling vs. monitoring of dispersal distance; fates of dispersing mites that land on soil substrates; plants as take-off platforms and landing targets for dispersers; and regional dispersal patterns and integrated mite management.

Survival and plant-prey finding by Neoseiulus fallacis (Acari: Phytoseiidae) on soil substrates after aerial dispersal.

In a greenhouse and in an open field, aspects of aerial and ambulatory dispersal of the phytoseiid mite, Neoseiulus fallacis (Garman) were studied with a focus on events that would occur after aerially dispersing mites had landed on soil or associated substrates. We measured recovery of predators on lima bean plants (Phaseolus lunatus L.) that were infested with the two-spotted spider mite, Tetranychus urticae Koch. Factors thought to affect movement and colonization were distance to a receiver unit from a release (landing) point, intervening soil surfaces such as clods, gravel, fine soil and grass, and management of soil surfaces such as mulching, watering or both. In the field, the effect of distance (0.11–1.76u2009m) from a landing point to a receiver unit was significant, with a negative log-linear relationship. Soil surfaces such as clods and management actions such as watering with mulching allowed for more capture of predators on bean plants with prey than did other treatments. Environmental conditions greatly affected survival of N. fallacis.Predators in the field that were present on bare soil suffered high mortality (ca. 90%) at fluctuating daytime conditions of 26.4u2009±u20094.8°C and 56u2009±u200913.4% RH. Predators only suffered 10% mortality in the greenhouse under the same setting, but under more controlled and favorable environmental conditions. Effects of environmental conditions, mode of dispersal and implications to biological control are discussed.

Release Strategies of Amblyseius womersleyi and Population Dynamics of Amblyseius womersleyi and Tetranychus urticae: I. Release position in pear

Abstract Biological control of twospotted spider mite, Tetranychus urticae by releasing Amblyseius womersleyi was applied in a protected pear orchard. A. womersleyi was released into a plastic house pear orchard to determine the effects of release positions on the control of T. urticae. Overall, A. womersleyi was higher in its density and controlled the population of T. urtice. The control was better in the plots where A. womersleyi was released into the canopy or canopy and ground cover than in the plots where A. womersleyi was not released or released into the ground cover. Also, A. womersleyi established its population on the ground cover more quickly in the canopy and ground cover release plot than in other plots. Initial settlement of A. womersleyi was important to control T. urticae in the pear orchard. The abundance of T. urticae was critical for the initial settlement of A. womersleyi regardless of release rates.

A New Finding of a the Predatory Mite, Amblyseius californicus (Acari: Phytoseiidae) in Jeju, Korea

Abstract Predatory mites in the Family of Phytoseiidae (Acari) are important components in mite biological control. Until now, a native predatory mite, Amblyseius womersleyi has been a subject of intensive studies for implementation of spider mite biological control in fruit orchards, while imported Phytoseiulus persimilis has been successfully implemented in greenhouse environments since 2002. Because of some ecological constraints of A. womersleyi as well as the field environments, spider mite biological control by A. womersleyi has not been successfully implemented. Therefore, demands for another feasible mite predator have increased. This paper reports a newly found predatory mite, Amblyseius californicus, known also as Neosiulus californicus from Jeju citrus orchards. This is the first record of field occurrence of this species in Korea. Some ecological characteristics of this species useful for biological control are also discussed.

Simulation Modeling of Twospotted Spider Mite Population Dynamics in Apple and Pear Orchards in Korea

Abstract Reliable prediction of pest population density plays a critical role in decision making for pest management. For this purpose, a stage-structured simulation model was constructed to predict the population dynamics of twospotted spider mite, Tetranychus urticae Koch in apple and pear orchards. Three external factors influential to spider mite population dynamics in Korean orchard systems are temperature, acaricide and precipitation. Temperature-dependent developmental parameters were mostly derived from experimental measures with a Korean strain of T. urticae. Immature development and adult longevity were fitted to the poikilotherm rate function (modified Sharpe and De-Michele model) with daily mean temperature while its variation and age-specific-oviposition, and -mortality were described by a three-parameter Weibull function relative to physiological age. Acaricidal effect and precipitation effect on T. urticae were expressed as exponential decay. Sensitivity tests and validation process provided good correlations to observed data from apple and pear orchards in a shorter period, but a little deviation in a longer period. Further improvement and implication of simulation model in integrated mite management are discussed.

Effects of sheltered ground habitats on the overwintering potential of the predacious mite Neoseiulus californicus (Acari: Phytoseiidae) in apple orchards on mainland Korea

Neoseiulus californicus (McGregor) (Acari: Phytoseiidae) is an effective predator of spider mites. In Korea, it is distributed on Jeju Island, but is never found further north on the mainland. Due to poor natural control of spider mites by native predatory mites in mainland orchards, commercialization of the Jeju Island strain of N. californicus on the mainland is currently being considered. We conducted two field experiments in mainland apple orchards during winter 2008 and 2009 to assess the effects of sheltered ground habitats on the overwintering potential of N. californicus. In the first experiment, all of the N. californicus individuals that were experimentally placed on bare ground died within 27xa0days, whereas 70% of mites sheltered by fallen apple leaves or urethane foam survived for more than 27xa0days. In the second experiment, individuals were released directly onto the ground, either with or without urethane foam. More individuals were found within urethane foam plots than in plots without foam. Sheltered ground habitats would be an important factor for N. californicus when selecting overwintering sites, and could eventually lead to enhanced winter survival. On the other hand, no live N. californicus individuals were found by the end of the winter in either experiment, which suggests that N. californicus could not successfully overwinter in the study area, even in sheltered ground habitats.

Overwintering Mite Diversity and Their Habitats in Apple and Pear Orchards of Korea with Emphasis on Phytoseiidae and Tetranychidae

Overwintering mite diversity and their habitats were studied in apple and pear orchards during 2002-2003 winter season. Twospotted spider mite was mostly found under the tree barks and fabric strips. European red mites were from crevices of twigs. Tydeid, tarsonemid and oribatid mites were mostly from soil and ground vegetation. Even in the protected overwintering habitat such as artificial fabric strip, twospotted spider mite suffered 81-91% mortality during winter. Predaceous phytoseiid mites found were Amblyseius womersleyi, A. makuwa, A. orientalis, A. rademacheri A. obtuserellus, and A. eharai. Amblyseius womersleyi was the most dominant species in both apple and pear orchards, followed by A. obtuserrellus in apple orchards and A. makuwa in pear orchards. Most phytoseiid mites were found on ground vegetation while their potential prey items were remained on the tree. Implication of the findings for conservation of beneficial mites and biological control of spider mite during season was further discussed.

Some Evidences of Aerial Dispersal of Twospotted Spider Mites from an Apple Orchard into a Soybean Field

Abstract Dispersal is an important component in population dynamics of a species as well as its distribution and persistence. Here, partial evidence of aerial dispersal of twospotted spider mite from an apple orchard to a contagious soybean field was described. Also, a mechanistic dispersal model was simulated using meteorological data and falling speed of twospotted spider mite. Model estimations were closely correlated with the observed distribution of twospotted spider mites within a soybean field. Further implication of the aerial dispersal and its modeling were discussed.

Olfactory Response and Feeding Preference of Liriomyza huidobrensis (Diptera: Agromyzidae) to Potato Cultivars

Abstract Liriomyza huidobrensis (Blanchard) is a serious invasive pest of potato in Korea. In sessile insect herbivores like leafminer flies, host plant choice is a critical decision made by adults for offspring survival, and one that is often influenced by host plant quality. In annual host plants like potato, leafminer choice is sometimes influenced by cultivar characteristics. To determine the basis of host selection, the odor and feeding preferences of adult L. huidobrensis were examined using a five-arm olfactometer offering a choice of five different potato cultivars: ‘Chubeak’, ‘Seohong’, ‘Goun’, ‘Dejima’, and ‘Sumi’. Preferences of adult leafminers varied significantly among potato cultivars. Liriomyza huidobrensis showed a preference for the Goun cultivar in both olfactory and adult feeding tests. When measured 2 wk after release onto actual plants, plant damage ratings and the number of mines were consistent with the feeding preference results. Further studies should examine the influence of cultivar characteristics on larval fitness and adult longevity to develop a resistant potato cultivar through the selection behavior of leafminers.