Sphaerocerids are now achieving pest status in mushroom houses.

During the course of our work with mushroom flies last year, we received several sticky traps from farms that contained an additional specimen to the usual assortment of sciarids and phorids. We identified this as the sphaerocerid fly, more commonly known as the ‘dung fly’.

Over 100 species of sphaerocerid are native to Britain and they occur in places often associated with decaying matter. For instance, species are found in decaying seaweed on the shore edge, in decaying grass cuttings and in animal dung.
The species associated with mushroom houses (Pullimosina heteroneura) can become a serious pest if numbers are allowed to build up. Infestations cause the same type of problems as those associated with sciarids and phorids such as disease transmission and reduced yields due to damaged compost. It is thought that, like sciarids, they are attracted to the compost and artificial light.

Sphaerocerids are  dark brown flies about 0.5 to 4 mm long.  They are very similar in appearance to phorids with a humped body and short antennae but if looked at very closely, (with good eye sight!) it can be seen that the eyes are red. Their movement  also resembles that of phorid flies as they run about in an erratic manner and appear to jump rather than fly.This similarirty to phorids may have resulted in the mis-diagnosis of sphaerocerid outbreaks so it is possible that sphaerocerid infestations have been more common than was previously thought.

Sphaerocerids mate immediately after emergence from the pupa and the eggs are laid close to the larval food source some 5-19 days later. After 24 - 48 hours, the eggs hatch into white larvae that are 1 to 5 mm long with 12 segments. They look rather like small housefly maggots. After 3 moults these larvae turn into pupae which are an elongated cylindrical structure, tapering at one end and turning from creamy white to brown as they mature. It takes from 7 to 18 days for the flies to complete a generation, a little quicker than sciarids, and the adults can live for several weeks compared to the short 3-5 day life span of adult sciarids.

Last year MicroBio was contacted by Blue Prince mushrooms and HRI identified the flies on their farm as Sphaerocerids. Once identified, MicroBio began work to determine if Nemasys M could control this new pest. Nemasys M was applied to the casing of one half of the house and the other half was left untreated. Samples were then taken each week throughout the case run and the numbers of flies emerging were monitored. This method  records exactly what is happening in the casing.

FIG 1.(more pictures) Summarises the results of this trial.

Six days after casing, flies began emerging from the untreated samples and continued each week until the end of the case run. By comparison, no flies emerged from the casing treated with Nemasys M during the entire length of the case run.  Blue prince mushrooms  believe that they can achieve better control with Nemasys M than with previous chemical products and can  effectively control their Sphaerocerid  populations.

• Sphaerocerids are now achieving pest status in mushroom houses.
  
  
• Their similarity in appearance and behaviour to phorids, suggests that they may have been previously mis- identified.
  
  
• Nemasys M controls Sphaerocerids.
  
  
• Ensure that your pest is correctly identified.