Takayuki Mitsunaga

Bio: Takayuki Mitsunaga is an academic researcher from National Agriculture and Food Research Organization. The author has contributed to research in topics: Braconidae & Aphid. The author has an hindex of 10, co-authored 35 publications receiving 270 citations. Previous affiliations of Takayuki Mitsunaga include National Agricultural Research Centre.

Influence of food supply on longevity and parasitization ability of a larval endoparasitoid, Cotesia plutellae (Hymenoptera : Braconidae)

Abstract: The influence of food supply on the survival and oviposition ability of Cotesia plutellae, the larval parasitoid of the diamondback moth, Plutella xylostella, was examined in the laboratory The longevity of the parasitoid decreased drastically under a lack of sugar availability The oviposition ability, evaluated by functional response to host density, was highly suppressed by a lack of food supply Thus, sugar availability is a very important condition for the effective utilization of C plutellae as a biological control agent of P xylostella in greenhouses

Time allocation of Orius sauteri in attacking Thrips palmi on an eggplant leaf

Abstract: Orius sauteri (Poppius) (Heteroptera: Anthocoridae) is a polyphagous predator used as a biological control agent of palm thrips, Thrips palmi (Karny) (Thysanoptera: Thripidae). We studied O. sauteri’ s searching efficiency, time allocation on a leaf, leaving tendency, and attacking of prey. Approximately 78% of the encountered prey was eaten. Searching for prey was concentrated for 86% of the time on the lower leaf side, where palm thrips are usually found. Patch residence times on empty leaves were different from those on leaves with T. palmi larvae. Walking activity was not affected by the thrips density, and walking took place during 64% of the total search time. The leaving tendency of O. sauteri was affected by the time from patch entry and the presence or absence of palm thrips, but not by the thrips density. If prey were present, the leaving tendency decreased (multiplication factor 0.327), resulting in longer giving-up times than when no prey was present. The fact that the leaving tendency increases when patch exploitation lasts longer suggests that not much time is wasted on patches where encounters with prey are scarce.

Larval Cannibalism and Intraguild Predation Between the Introduced Green Lacewing, Chrysoperla carnea, and the Indigenous Trash-Carrying Green Lacewing, Mallada desjardinsi (Neuroptera: Chrysopidae), as a Case Study of Potential Nontarget Effect Assessment

Abstract: To study the potential competitive risk of the introduced Chrysoperla carnea (Stephens) on the indigenous trash-carrying chrysopid Mallada desjardinsi (Navas), we studied the occurrence of cannibalism and intraguild predation (IGP) at different prey densities. In C. carnea, 100% cannibalism was observed in the absence of aphids. In M. desjardinsi, cannibalism was also observed, but absence of cannibalism occurred at 35% in pairs of second- + third-instar larvae and at 70% in pairs of third- + third-instar larvae. In pairs of M. desjardinsi larvae whose trash package had been artificially removed, all third-instar larvae ate second-instar larvae. The trash package may play a role in the reduced mortality of younger larvae by cannibalism. IGP occurred in all pairs. In the absence of aphids, the interaction was symmetric between second-instar larvae, but asymmetric for second- versus third- and third- versus third-instar larvae, and the interaction was similar when M. desjardinsi larvae with or with...

Laboratory Hybridization Between the Introduced and the Indigenous Green Lacewings (Neuroptera: Chrysopidae: Chrysoperla) in Japan

Abstract: We report on laboratory hybridization between the indigenous Chrysoperla nipponensis and its close relative, C. carnea, which has been imported since 2001 from Germany to Japan as a biological control agent. Interspecific hybrids were obtained, and fully viable and fertile F1 and F2 generations were produced. Crosses between C. carnea females and C. nipponensis males showed 41.3% fertility, but the reciprocal cross showed only 9.5% fertility. Despite the low fertility of interspecific crosses, most F1 hybrids were fertile and were successfully backcrossed to both parental species. However, F1 males from C. carnea females × C. nipponensis males showed low fertility (zero except for 20% in one case) when crossed with any females (F1 or backcross). In the one combination resulting in 20% fertility, an extremely long preoviposition period was observed, caused presumably by a mating delay. The absence of change in hatchability, adult emergence rate, total developmental period, or deviation from the 50...

Comparison of the effects of landscape composition on two mirid species in Japanese rice paddies

Abstract: Two rice bug species, Stenotus rubrovittatus (Matsumura) and Trigonotylus caelestialium (Kirkaldy) (Hemiptera: Miridae), are major rice pests in Japan. The populations of these insects are maintained by widely distributed host plants and by a broad range of movements among resource patches. To develop an effective pest management strategy for a region where two rice bug species coexist, the impacts of the surrounding landscape and of weed-infested field boundaries on the field abundances of the two rice bug species were compared. Field abundances of the two species were estimated using the sweep-netting technique. The number of weed-infested field boundaries was also counted within a 100 m radius around 14 study paddies at three sites in Japan. The distinctive features of the surrounding landscape furnished the best predictor at a spatial scale radius of 300 m for S. rubrovittatus and at 200–300 m for T. caelestialium. The abundances of both species increased as the amounts of weed-infested area and reclaimed land increased. The size and number of sources also affected the two rice bug species. These results emphasize that adequate field boundary management can reduce the risk of high pest abundance in the fields, even when an extensive weed-infested area exists within the functional scale of the species.

Mechanism and consequences for avoidance of superparasitism in the solitary parasitoid Cotesia vestalis.

Abstract: A parasitoid’s decision to reject or accept a potential host is fundamental to its fitness. Superparasitism, in which more than one egg of a given parasitoid species can deposit in a single host, is usually considered sub-optimal in systems where the host is able to support the development of only a single parasitoid. It follows that selection pressure may drive the capacity for parasitoids to recognize parasitized hosts, especially if there is a fitness cost of superparasitism. Here, we used microsatellite studies of two distinct populations of Cotesia vestalis to demonstrate that an egg laid into a diamondback moth (Plutella xylostella) larva that was parasitized by a conspecific parasitoid 10 min, 2 or 6 h previously was as likely to develop and emerge successfully as was the first-laid egg. Consistent with this, a naive parasitoid encountering its first host was equally likely to accept a healthy larva as one parasitized 10 min prior, though handling time of parasitized hosts was extended. For second and third host encounters, parasitized hosts were less readily accepted than healthy larvae. If 12 h elapsed between parasitism events, the second-laid egg was much less likely to develop. Discrimination between parasitized and healthy hosts was evident when females were allowed physical contact with hosts, and healthy hosts were rendered less acceptable by manual injection of parasitoid venom into their hemolymph. Collectively, these results show a limited capacity to discriminate parasitized from healthy larvae despite a viability cost associated with failing to avoid superparasitism.

Biological Control: Ecology and Applications

Abstract: Biological control is the suppression of populations of pests and weeds by living organisms. These organisms can provide important protection from invasive species and protect our environment by reducing the need for pesticides. However, they also pose possible environmental risks, so biological control interventions must be undertaken with great care. This book enhances our understanding of biological control interactions by combining theory and practical application. Using a combination of historical analyses, theoretical models and case studies, with explicit links to invasion biology, the authors cover biological control of insects, weeds, plant pathogens and vertebrate animals. The book reflects increasing recognition of risks over the past 20 years, and incorporates the latest technological advances and theoretical developments. It is ideal for researchers and students of biological control and invasion biology.

Mechanisms for flowering plants to benefit arthropod natural enemies of insect pests: prospects for enhanced use in agriculture.

Abstract: Reduction of noncrop habitats, intensive use of pesticides and high levels of disturbance associated with intensive crop production simplify the farming landscape and bring about a sharp decline of biodiversity. This, in turn, weakens the biological control ecosystem service provided by arthropod natural enemies. Strategic use of flowering plants to enhance plant biodiversity in a well-targeted manner can provide natural enemies with food sources and shelter to improve biological control and reduce dependence on chemical pesticides. This article reviews the nutritional value of various types of plant-derived food for natural enemies, possible adverse effects on pest management, and the practical application of flowering plants in orchards, vegetables and field crops, agricultural systems where most research has taken place. Prospects for more effective use of flowering plants to maximize biological control of insect pests in agroecosystem are good but depend up on selection of optimal plant species based on information on the ecological mechanisms by which natural enemies are selectively favored over pest species.