First finding of the parasitic fungus Hesperomyces virescens (Laboulbeniales) on native and invasive ladybirds (Coleoptera, Coccinellidae) in South Africa.

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Abstract

Hesperomyces virescens is a fungal ectoparasite (Laboulbeniales) that infects adult ladybirds. Research has recently focused on this parasite due to the discovery of its prevalence on the globally invasive harlequin ladybird Harmonia axyridis and for its potential use in studies of co-evolution and pathogen spread. We collected adults from ten species of ladybirds in the Western Cape Province, South Africa, and screened for the presence of H. virescens. Infections with H. virescens were found in the samples of two species, H. axyridis and the native Cheilomenes propinqua. This marks the first record of H. virescens on H. axyridis from the African continent and the first record on Cheilomenes worldwide.

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Infection of Harmonia axyridis (Coleoptera: Coccinellidae) by Hesperomyces virescens (Ascomycetes: Laboulbeniales): Role of mating status and aggregation behavior

Alexander Weir, Christine A. Nalepa (2007)

The ectoparasitic fungus Hesperomyces virescens was studied on Harmonia axyridis in North Carolina, in the southeastern United States. A primary goal was to investigate transmission of the disease by examining the correlation between the pattern of fungal infection and seasonal change in host behavior. Beetles were collected as they arrived at their winter quarters at two sites; in one site they were also subsampled at mid- and late winter. Insects were sexed and weighed, fungal thalli were counted, and their location on the host body mapped; spermathecae of females were examined for sperm. Infection levels varied between sites, differed significantly between the sexes in one site but not the other, and increased by approximately 40% during winter. The distribution of thalli on the body changed seasonally, in concert with behavioral changes in the host. At fall flight, thalli were found most often on the posterior elytra of mated females, virgin females, and males. This is suggestive that the disease had been spread among both sexes via successful and failed copulation attempts; however, the relatively low incidence of infection on the male venter does not fit the sexual transmission scenario. During winter, thallus location shifts in concert with beetle aggregation behavior, with infections more often located on the head and legs. Fresh weight of beetles decreased by approx. 20% during winter, but was not affected by disease status. Prior to spring flight, uninfected females were preferred as mating partners, but the probable relationship between female age and infection status complicates interpretation of the data.

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Laboulbenia slackensis and L. littoralis sp. nov. (Ascomycota, Laboulbeniales), two sibling species as a result of ecological speciation.

André De Kesel, Danny Haelewaters (2024)

Laboulbenia littoralis is described from the halobiont Cafius xantholoma (Coleoptera, Staphylinidae); it previously was misidentified and not properly documented. Morphologically the new species belongs to a group of carabidicolous taxa similar to Laboulbenia pedicellata and especially Laboulbenia slackensis. It is generally accepted that the specificity of Laboulbeniales is based on their need for substances from the host. In this relatively strict context, shifts between unrelated hosts are difficult to explain. We present morphological and ecological evidence supporting the hypothesis that these fungi are capable of shifting between unrelated hosts as long as they share the same habitat. Adaptation to a particular environment, combined with a reduced dependence from specific nutrients of the host, explains the proposed interfamilial host shift.

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Influence of Host Gender on Infection Rate, Density and Distribution of the Parasitic Fungus, Hesperomyces virescens, on the Multicolored Asian Lady Beetle, Harmonia axyridis

E. Riddick (2006)

Hesperomyces virescens Thaxter (Laboulbeniales: Laboulbeniaceae) is a parasitic fungus that infects lady beetles (Coleoptera: Coccinellidae) via horizontal transmission between adults at overwintering and feeding sites. The differential behavior of male and female hosts could have profound effects on intensity of infection and positioning of fungus on the host's integument. The influence of host gender on infection rate, density and distribution of this parasite on the multicolored Asian lady beetle, Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae), was determined at a feeding site. Adult H. axyridis were sampled from pecan, Carya illinoinensis (Wangenh.) K. Koch, trees in northern Mississippi, USA, during summer and early fall 2003–2004. Results indicated that the behavior of male or female beetles on pecan trees had only a limited effect on the intensity of infection. When averaged over the entire season, the percentage of H. axyridis infected with H. virescens was not influenced by host gender. In 2003, a seasonal average of 54 and 39% of males and females, respectively, were infected; whereas in 2004, 36 and 41% of male and female beetles, respectively, were infected. The percentage of males infected with H. virescens was correlated with the number of males captured at the site in 2003; infection rate decreased as male abundance increased. Infection rate did not correlate with female abundance in 2003 or male or female abundance in 2004. Host gender had a considerable effect on the density and distribution of the fungus. Hesperomyces virescens mature thalli were denser on male rather than female beetles. Also, thallus density was often greatest on the elytra, meso- and metathorax, and abdomen of males and elytra of females, than on other body parts, in 2003. In 2003 and 2004, approximately 59 and 97% and 67 and 96% of males and females, respectively, had mature thalli distributed on the elytra. Prevalence of H. virescens thalli on the dorsum of H. axyridis females suggests that mating behavior is important in fungal transmission. However, prevalence of thalli on the dorsum of H. axyridis males suggests that behaviors other than mating contribute to the transmission of H. virescens onto male beetles. Spread of H. virescens ascospores from infected to uninfected H. axyridis adults of different generations, at feeding sites, might be vital to maintaining stable populations of the fungus.