Intraguild predation (IGP) is defined as the killing and eating of prey species by a predator that also can utilize the resources of the prey. It is mainly reported among carnivores that share common herbivorous prey. However, a large chewing herbivore could prey upon sedentary and/or micro herbivores in addition to utilizing a host plant. To investigate such coincidental IGP, we observed the behavioral responses of the polyphagous mite Tetranychus kanzawai Kishida (Acari: Tetranychidae) when its host plant Cayratia japonica (Thunb.) Gagnep. (Vitaceae) was attacked by hornworms, Theretra japonica Boisduval (Sphingidae) and T. oldenlandiae Fabricius (Sphingidae). We also examined an interaction between the oligophagous mite Panonychus citri McGregor (Acari: Tetranychidae) and caterpillars of the swallowtail Papilio xuthus L. (Papilionidae) that share citrus plants as their main food source. Although all T. kanzawai and some active stage P. citri tried to escape from the coincidental IGP, some were consumed together with eggs, quiescent mites, and host plant leaves, suggesting that coincidental IGP occurs on spider mites in the wild. Moreover, neither hornworms nor swallowtail caterpillars distinguished between spider mite-infested and uninfested leaves, suggesting that the mite-infested leaves do not discourage caterpillar feeding. The reasons that the mites have no effective defense against coincidental IGP other than escaping are discussed.

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The effect of a red insect-proof net, a predatory mite, Amblyseius swirskii Athias-Henriot, and granular formulation of an entomopathogenic fungus, Metarhizium anisopliae (Metschn.) Sorokin on melon thrip, Thrips palmi Karny, was investigated on greenhouse cucumber from August to November in 2013, 2014, and 2015. A red insect-proof net was placed in the treated plot, and 50,000 A. swirskii were released per 10 a, and 5 kg of M. anisopliae granules were applied per 10 a. In the control plot, a white insect-proof net was used and no biological pesticides were applied. In 2013 and 2015, the population density of thrips was lower in the treated plot than in the control plot. In 2014, the population density of adult thrips was similar in both plots, and the number of larval thrips was lower in the treated plot than in the control plot. These results suggest that the IPM system utilizing a red insect-proof net in combination with A. swirskii, and M. anisopliae can effectively control thrips.

Enclosing with a red insect-proof net and defuse-reflection mulch sheets were set up in an open fig orchards in Osaka Prefecture in 2017. The dominant thrips species found on the sticky color traps were Thrips tabaci Lindeman from late May to early June and Frankliniella intonsa (Trybom) from mid-June to mid-July. Thrips hawaiiensis (Morgan) was dominant inside fig fruits. The use of these materials effectively prevented thrips from immigrating into the fig orchards, reducing population numbers and infestation of figs. We recommend placing these materials by the middle of May.

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