The effect of tibia morphology on vector competency of mushroom sciarid flies

Mushroom sciarid flies Lycoriella ingenua (Dufour) and Bradysia ocellaris (Comstock) are major pests of cultivated mushrooms, Agaricus bisporus (Lange) Imbach. The economic threshold of these pests is very low because they vector pathogens across mushroom beds, e.g. Verticillium fungicola which causes ‘dry bubble’ disease. Under controlled conditions, B. ocellaris transported more V. fungicola spores than L. ingenua from infected to sterile culture plates. Similar results were obtained when L. ingenua and B. ocellaris were collected from a growing room infected with V. fungicola then introduced onto sterile culture plates for 90 min. The external morphology of B. ocellaris and L. ingenua was examined using scanning electron microscopy. The micrographs showed clusters of V. fungicola spores attached to the inner side of a comb‐like row of bristles on the fore tibia of B. ocellaris whereas L. ingenua does not possess an equivalent structure on the fore tibia. These morphological differences are the most probable explanation for the greater competence of B. ocellaris as a vector of V. fungicola compared with L. ingenua.