This sciarid is a common and often important pest that can check the growth of glasshouse cuttings, seedlings and young pot plants, including cucumber, lettuce, melon and various ornamentals. Attacked plants may also wilt and die, especially in sunshine. Less frequently, when eggs are deposited on leaves, the larvae skeletonize the foliage.
Adult sciarids are very active, and are often seen flitting or scurrying about at the base of cuttings, seedlings or older plants. The egg-laying females are much attracted to dried blood fertilizer and to steam-sterilized soil; each will deposit 100 or more eggs in the soil close to host plants. Eggs hatch several days later, the incubation time varying considerably according to temperature. The larvae feed for 3-4 weeks and usually attack the root hairs; when fully fed, they construct silken cocoons within which to pupate, and adults emerge about a week later. More rarely, eggs may be placed directly onto plant tissue; the larvae then feed on the leaf tissue and may eventually pupate on the foliage. Under suitable conditions breeding is continuous.
Adult 3.0-3.5 mm long, black, with a greyish-brown abdomen; eye bridge present (see Fig. 87) (cf. cucumber sciarid fly, Pnyxia scabiei, p. 168); legs yellowish; antennae relatively short and thick; palps 3-segmented (cf. cucumber sciarid fly, P. scabiei, p. 168). Egg 0.2 x 0.1 mm, oval, translucent-whitish. Larva up to 6 mm long, elongate, translucent-whitish; head shiny black.
Bradysia amoena (Winnertz)
This relatively small, dark-bodied species occurs commonly in association with pot plants. The adults are similar to those of Bradysia paupera (above) but have longer, thinner antennae; they are active at virtually any time of year and frequently attract attention in dwelling houses; the larvae can cause injury to seedlings and small plants but are rarely important.
Bradysia aprica (Winnertz)
Infestations of this small, widely distributed sciarid often occur in glasshouses, where the larvae cause minor damage to pot plants. Adults are dark-bodied with pale halteres, pale legs and clear wings.
Bradysia brunnipes (Meigen)
This species is often common in mushroom houses, and the adults are sometimes a nuisance to pickers. The larvae feed in the casing. Although implicated in the spread of diseases, they do not damage the mushrooms directly (cf. mushroom sciard fly, Lycoriella auripila, p. 168). Adults are blackish (females have a paler abdomen), with slightly smoky wings (wing length: 3.0-4.5 mm) and yellow halteres.
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