Dispersion of Aphytis yanonensis and Coccobius fulvus, introduced parasitoids of arrowhead scale, Unaspis yanonensis in Kyushu in 1987. I. Northern part of Kyushu.

Hashimoto, Syoichi; Miyaji, Katsuhiko; Gyoutoku, Yutaka; Watanabe, Yutaka; Kai, Ippei; Tamura, Itsumi; Ujiye, Takeshi; Kashio, Tomotoshi

doi:10.4241/kyubyochu.34.161

Cited by 4 publications

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“…In 1987, one of the authors (T. Itioka) released two species of parasitoids as biological controls in an orchard that was centrally located in the study area (Itioka et al., 1997). Although exactly when the parasitoids invaded the study site and became established is unknown, they probably invaded within a year after the groves were abandoned, as both species disperse at about 10 km per year (Ohkubo et al., 1988). We analysed parasitism by C .…”

Section: Methodsmentioning

confidence: 99%

Is spatial density‐dependent parasitism necessary for successful biological control? Testing a stable host–parasitoid system

Matsumoto

Itioka

Nishida

2004

Entomologia Exp Applicata

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One of the most famous examples of successful, classical biological control in Japan is the introduction of the parasitoids Coccobius fulvus and Aphytis yanonensis against the citrus pest arrowhead scale Unaspis yanonensis. Together, they comprise a host-parasitoid system that has been demonstrated to be stable. To test the conventional theory that successful biological control of pests occurs through the establishment of a low stable equilibrium, brought about by the density-dependent responses of natural enemies to the pest species, sampling was carried out at five sites in the field during 2000 and 2001 to examine the relationship between the rate of parasitism by C. fulvus and the density of its host. The data were analysed using three statistical techniques at nine spatial scales. Contrary to conventional theoretical predictions, each method of analysis detected very little densitydependence at any spatial level in this study. Parasitoid aggregations independent of host density were not sufficient to stabilise host-parasitoid interactions. Our results suggest that neither spatial densitydependent nor density-independent parasitism is necessary for successful biological control, or for the stability of the host-parasitoid system. We propose an alternative mechanism: a spatial refuge induced by parasitoid introduction may stabilise a system.

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Section: Methodsmentioning

confidence: 99%

Is spatial density‐dependent parasitism necessary for successful biological control? Testing a stable host–parasitoid system

Matsumoto

Itioka

Nishida

2004

Entomologia Exp Applicata

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A Simulation model for the arrowhead scale (Hemiptera: Diaspididae) population dynamics on citrus trees in relation to pest‐management programs

Adachi¹,

Korenaga²

1992

Population Ecology

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Summary A mathematical model was constructed describing population dynamics of the arrowhead scale, Unaspis yanonensis Kuwana. The population occurrence patterns simulated by the model from 1971 to 1976 were relatively consistent with the actual findings in the field. The effects of control tactics for this pest were examined on the basis of the model. Effective timing of insecticide (petroleum oil and organophosphorous insecticide) application was indicated to be 40 days after the initial appearance of 1st‐instar nymphs in both the 1st and 2nd generations of the host. The number of overwintering adult females in May of the next year (i.e., the starting point of the next year's population) decreased linearly with the increment in the degree of insecticide coverage. The pest populations were expected to be kept to low densities by petroleum oil sprays alone for the 1st generation when overall, complete coverage was accomplished. Examination of the effects of two introduced parasitoids, Aphytis yanonensis and Coccobius fulvus, showed that they were able to control the scale population by themselves when more than 70% parasitism was achieved. When petroleum oil was applied to overwintering adults (termed winter petroleum oil) at the degree of coverage of 0.8, host populations were reduced by ca. 60% parasitism. When the winter petroleum oil was combined either with additional petroleum oil 40 days after the initial appearance of 1st‐instar nymphs of the 1st generation or with an organophosphorous insecticide 40 days after the initial appearance of 1st‐instar nymphs of the 2nd generation (degree of coverage=0.8 in each case), 40% parasitism led the reduction of the pest population. The most desirable control program was considered to be one in which winter petroleum oil was used every year and additional petroleum oil or an organophosphorous insecticide was also used in those years when host density was high.

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Climatic and intertrophic effects detected in 10‐year population dynamics of biological control of the arrowhead scale by two parasitoids in southwestern Japan

Tuda¹,

Matsumoto

Itioka

et al. 2005

Population Ecology

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Relative effects of weather and three‐trophic interactions were studied for a classical biological control system consisting of the arrowhead scale Unaspis yanonensis, known formerly as a serious pest of the Satsuma mandarin orange Citrus unshiu, and its two introduced parasitoids, Coccobius fulvus and Aphytis yanonensis. Yearly population responses of the three insect species on a per‐tree basis for up to 10 years at two orange groves were analyzed by general linear models, with a backward stepwise procedure, to select among abiotic (summer/winter temperature and rainfall) and biotic (densities of the three insect species and orange bearing in the previous years) independent variables. Temperature positively affected the arrowhead scale and the two parasitoids. A negative correlation of rainfall was detected for all three insect species. Mandarin fruiting showed negative delayed density dependence, thereby supporting the observed alternate bearing phenomenon in mandarins, presumably due to physiological imbalance triggered by climatic factors. The arrowhead scale was negatively correlated with fruit production in the preceding years, possibly due to reduced resistance in subsequent years of mast fruiting. We found a negative correlation of the arrowhead scale with Coccobius only in a single grove and none with Aphytis. Thus, it appears that bottom‐up forces may be more important than top‐down control by the parasitoids in the post‐transient phase of this system.

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Dispersion of Aphytis yanonensis and Coccobius fulvus, introduced parasitoids of arrowhead scale, Unaspis yanonensis in Kyushu in 1987. I. Northern part of Kyushu.

Cited by 4 publications

References 0 publications

Is spatial density‐dependent parasitism necessary for successful biological control? Testing a stable host–parasitoid system

Is spatial density‐dependent parasitism necessary for successful biological control? Testing a stable host–parasitoid system

A Simulation model for the arrowhead scale (Hemiptera: Diaspididae) population dynamics on citrus trees in relation to pest‐management programs

Climatic and intertrophic effects detected in 10‐year population dynamics of biological control of the arrowhead scale by two parasitoids in southwestern Japan

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