Mushrooms are susceptible to a range of diseases and pests that can cause serious crop loss. Effective pest and pathogen control is a very important factor for the maintenance of efficient production of cultivated mushrooms. Integrated pest management in mushrooms is reliant upon four main principals/elements: sanitation, exclusion, monitoring and pest control. Bradysia ocellaris (Comstock) and Lycoriella ingenua (Dufour) (Diptera: Sciaridae) are major pests of cultivated mushrooms, Agaricus bisporus (Lange) Imbach. These pests cause losses in yield through larval damage of the compost, mycelium and sporophores, and affect the structural features of the compost itself. Adult flies of these species also act as vectors for the introduction of mites and fungal diseases in cultivated mushrooms.

Lycoriella ingenua is one of the major pests of cultivated mushrooms, Agaricus bisporus (Lange) Imbach. Insecticide resistance among mushroom sciarid populations has been reported from other countries, and there is a need to determine the toxicity of currently approved and potential pesticides to sustain control of mushroom sciarid populations in Australia. The present study investigated the toxicity of six commercial formulations of insecticides or biopesticides against third instar larvae of L. ingenua using laboratory bioassays. Insecticide treatments were incorporated into the growing medium for sciarid larvae and the concentration of the pesticide, which killed 90% of the test population (LD90) determined the efficacy of selected insecticides. Triflumuron was the most effective insecticide against L. ingenua with an LD90 of 53.12 mg active ingredient (a.i.)/m 2 followed by cyromazine (LD90, 179.68 mg a.i./m 2 ) and diazinon (LD90, 261.72 mg a.i./m 2 ). Abamectin and Bacillus thuringiensis ssp. israelensis were ineffective against L. ingenua. Steinernema feltiae, an entomopathogenic nematode, reduced the number of third instar larvae of L. ingenua only when applied at a higher rate (LD90, 732 422 nematodes/m 2 ) than was recommended on the label.

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.

The results obtained from this study suggest that incorporation of insecticides into both compost and casing is required to control a moderate to high pressure of insect pests. There were no significant yield reductions as a result of the incorporation of pesticides in the Australian mushroom-growing system.

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