Like cluster flies, Yellow Swarming Flies (Thaumatomyia notata) are normally active in places where lights are left on all the time. This population was found in an unused room in a block of flats in Haywards Heath. These pests look for places with nooks and crannies to overwinter so it’s best to get on top of the problem before winter. In this case, there were lots of dead flies in the light fittings which could cause a fire risk if not removed.
We used ULV (ultra-low volume) pesticide to treat the infestation which means it can be applied in a very controlled way.
Yellow Swarming flies, often referred to as Yellow Cluster Flies or Grass Flies, are a common seasonal nuisance pest particularly during late summer and autumn. They are easily identified by their distinctive yellowish colouring and tendency to gather in large numbers, often around windows, ceilings or light fittings. These flies are typically attracted to warm, sheltered environments, such as lofts, roof spaces and upper rooms where they cluster in groups to rest or over winter. While they do not bite or cause direct harm, their persistent presence can be distressing and unhygienic, especially in commercial or residential settings. Effective control usually involves a combination of insecticidal treatments, entry-point sealing and environmental management to prevent re-infestation.