The study reported examines the spectral specific responses of adult insect pests of mushroom (Agaricus bisporus (Lange) Imbach) cultivation to light traps and the potential for use of light trapping as a pest management tool within commercial mushroom production. Lycoriella ingenua (Dufour) (Diptera: Sciaridae) and Megaselia halterata (Wood) (Diptera: Phoridae) were the principal insect pests at the experimental site. Adult L. ingenua and M. halterata were positively phototactic and relatively high numbers were attracted to relatively low light emissions from light trap sources of differing wavelengths. Yellow sticky traps at a height of 1·7 m collected more flies of both species than traps located at crop height (0·6 m). Adult female L. ingenua were more numerous than males in all trap types suggesting that they were more active fliers than male counterparts. Numbers of females recorded in light traps greatly exceeded those in yellow sticky traps, indicating greater photo-responsiveness. Light wavelengths between 300–650 nm attracted greater numbers of adult L. ingenua than wavelengths exceeding 700 nm. This species was present throughout the year but was most abundant between May and December. Adult M. halterata were less numerous than adult L. ingenua in all trap types and particularly on yellow sticky traps at crop level. The lower disparity between numbers of adult M. halterata on light traps and yellow sticky traps suggests that adults of this species are not as photosensitive as adult L. ingenua. The observed response of adult M. halterata to light sources of different wavelengths was variable within the range 300–>700 nm. Adult M. halterata were most abundant between June and November.