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The ambrosia beetle, Euwallacea interjectus, is a wood-boring pest and a vector of Ceratocystis ficicola, a pathogenic fungus causing fig (Ficus carica) wilt disease (FWD) in Japan. The ambrosia fungi, Fusarium kuroshium and Neocosmospora metavorans, have been frequently isolated from heads (including mycangia) of wild and reared adult female E. interjectus, respectively. However, the exact mechanisms driving FWD as well as the interactions between F. kuroshium and C. ficicola in fig orchard remain unclear. To verify the role of the mycangial fungi in the FWD progression, fig saplings were subjected to inoculation treatments (T1, F. kuroshium; T2, N. metavorans, reference positive control; T3, C. ficicola; T4, F. kuroshium + C. ficicola, realistic on-site combination). T3 and T4 saplings began wilting approximately 12 days after inoculation, leading to eventual death. Median duration from inoculation to death of the T4 saplings was approximately four days significantly faster than that of the T3 saplings. Xylem sap-conduction test indicated that dysfunction and necrosis area were considerably wider in the T4 saplings than in T3 saplings. These results demonstrate that the synergistic action of F. kuroshium and C. ficicola contributed to accelerated wilting in the saplings. Based on these discoveries, we proposed a model for system changes in the symbiosis between E. interjectus and its associated fungi in FWD in Japan. [ABSTRACT FROM AUTHOR]

Ambrosia beetles bore into host trees, and live with fungi symbiotically that serve as a food source. However, it is challenging to directly observe these beetles in the wild. In this study, Euwallacea interjectus (Blandford) (Coleoptera: Curculionidae: Scolytinae), a pest of fig trees in Japan, were reared under artificial conditions to emulate the behavior of ambrosia beetle. Fungi were isolated from the adult females of E. interjectus to identify the species associated with secondary symbiosis. In total, nine filamentous fungi and one yeast were identified using morphological characteristics and DNA sequence data. Neocosmospora metavorans (Hypocreales: Nectriaceae), Fusarium sp. (Hypocreales: Nectriaceae), that is undescribed, and Meyerozyma guilliermondii (Saccharomycetes: Saccharomycetales) (yeast) were isolated more frequently from the head (including from mycangia, the fungus-carrying organ) than from the thorax and abdomen of adult beetles. Neocosmospora metavorans was the dominant species isolated from 12 out of 16 heads at 200 to 3300 CFUs/head, compared to the primary mycangia fungus from wild beetles, i.e., Fusarium kuroshium (Hypocreales: Nectriaceae). Temperature had a marked effect on fungal growth in the three symbiont species. Our results represent a major paradigm shift in understanding beetle–fungal interactions, as they show specific symbiont switching can occur in different nesting places. [ABSTRACT FROM AUTHOR]

Ficus carica plantations in Japan were first reported to be infested by an ambrosia beetle species, identified as Euwallacea interjectus , in 1996. The purpose of this study was to determine the symbiotic fungi of female adults of E. interjectus emerging from F. carica trees infected with fig wilt disease (FWD). Dispersal adults (51 females) of E. interjectus , which were collected from logs of an infested fig tree in Hiroshima Prefecture, Western Japan, were separated into three respective body parts (head, thorax, and abdomen) and used for fungal isolation. Isolated fungi were identified based on the morphological characteristics and DNA sequence data. Over 13 species of associated fungi were detected, of which a specific fungus, Fusarium kuroshium , was dominant in female head (including oral mycangia). The plant-pathogenic fungus of FWD, Ceratocystis ficicola , was not observed within any body parts of E. interjectus. We further discussed the relationship among E. interjectus and its associated fungi in fig tree. [ABSTRACT FROM AUTHOR]

Earwigs (Dermaptera), such as Forficula auricularia L., are important euryphagous predators for a wide variety of prey and can markedly influence the populations of orchard pests. Most previous studies on earwig feeding behaviour have not used adult beetles of the prey species; few researchers have focused on prey preference in earwigs. Some fragments of beetle exoskeleton and an earwig adult, Anisolabella marginalis (Dohrn), were found in the same cage, where adults of ambrosia beetle, Euwallacea interjectus (Blandford), were emerging from the logs of a fig tree infected with Ceratocystis canker (fig wilt disease). Thus, A. marginalis was suspected of being a predator of E. interjectus. To shed light on this issue, in the laboratory, we set up a test arena and observed and recorded behavioural interactions between A. marginalis and E. interjectus. E. interjectus was collected from the logs of fig trees and reared on an artificial diet, along with six different ambrosia beetle species, which were collected from a trap (baited with ethanol) and a fallen maple tree. A series of laboratory experiments demonstrated that A. marginalis is actually a predator of E. interjectus and other species of ambrosia beetle, indicating its a potential for use in effective pest control in the field. The predators frequently consume and tend to select their prey depending on prey size, rather than sex and beetle species. Furthermore, earwigs have alternative predatory strategies for dealing with seven different species, although they use their forceps to cut the body of most tested beetles. [ABSTRACT FROM AUTHOR]

To clarify the effects of asynchronous seed production among tree species on the population of seed predators, we investigated the relationship between the annual variation in production of mature acorns and the insect damage in those acorns of two sympatric oak species, Quercus variabilis Blume and Quercus serrata Thunb. ex Murray, over 4 years at two study sites. The annual variation in acorn production was noticeable, with a coefficient of variation (CV) at the two sites of 1.05 and 0.80 for Q. variabilis and 0.87 and 0.73 for Q. serrata. Annual fluctuation in acorn production by Q. serrata was synchronized between the two sites. Since annual fluctuation in acorn production was not synchronized between the two species, the CVs for the total acorn production by both oak species (0.83 and 0.62 at the two sites) were lower than those for Q. variabilis and Q. serrata alone. The rate of predation by the specialist predators ( Curculio weevils) on the acorns of both species was not related to the annual acorn crop size. Prolonged diapause of Curculio weevils might stabilize their populations. The rate of acorn predation by the generalist predators (tortricid moths) was also not related to the annual crop size. Asynchronous acorn production by the two oak species would help to stabilize the population. [ABSTRACT FROM AUTHOR]