Taxonomic review of the agricultural and forest pests of Bradysia spp. (Diptera: Sciaridae) in Japan

Pest species of a fungus gnat genus Bradysia Winnertz (Diptera: Sciaridae) injuring agricultural and forestry products in Japan, with a review on taxonomy of allied species

Masahiro Sueyoshi (a) , Shin-Ichi Yoshimatsu (b)

(a) Center for Biodiversity, FFPRI, Tsukuba, Ibaraki, Japan.

(b) National Agriculture and Food Research Organization, Tsukuba, Ibaraki, Japan.

Entomological Science、Wiley、July 2019 DOI：10.1111/ens.12373( External link )

Black-winged fungus gnats (Diptera: Sciaridae) are small mosquito-like insects causing damage to vegetables, crops and edible mushrooms and are sometimes detected from agricultural packing products. Because of their severe economic impact, effective pest control and countermeasures for each species are necessary. In Japan Bradysia impatiens (Figure a; body length, 1–2 mm) and its allied species had been considered as agricultural and forest pests. As they are so small, similar and taxonomically confused, they were often treated as a single species or many scientific names were applied to the complex.

Therefore, we reviewed their taxonomy and concluded that a species name, B. impatiens, should be used for a pest fungus gnat commonly occurring in Japan. In addition, we considered B. paupera, attacking edible fungi in Japan, formerly treated as a synonym of B. impatiens, as a distinct species based on the morphology of the male genitalia (Figures c, d). We also identified an unknown pest species of Welsh onion recorded from a part of Japan since 2014 as B. odoriphaga originally known from China. We clarified the morphological differences of B. odoriphaga, B. impatiens and B. paupera (Figures c–e). These results will be useful in the development and application of appropriate pest control techniques according to sciarid species encountered at the production sites.

Figures: (a) Adult male and (b) male genitalia of Bradysia impatiens, (c–e) tip of the gonostylus of B. impatiens, B. paupera and B. odoriphaga. The arrow point at small projections present at the tip of the gonostylus of B. impatiens (c) and B. paupera (d), and the outer side of the gonostylus of B. odoriphaga (e). In addition, the gonostylus of B. paupera (d) is thin, with four strong bristles (thick bristles in the red circle), whereas those of (c) B. impatiens and (e) B. odoriphaga are thick, with five or more numbers of strong bristles (thick bristles in the red circles).