Frequently during the warm summer months, rattailed maggots are reported as a nuisance pest migrating from livestock lagoons and manure pits. These creatures are not a problem as long as they remain in the liquid manure pit. However, they are known to move out of the pit, or lagoon, in large numbers, contaminating livestock feed, accumulating in electrical boxes and causing short circuits and congregating in stacks of egg cartons and other unwanted places. The maggots migrate to a drier place for pupation.
Rattailed maggots, known as the larval or immature stage of Syrphid flies, are about 1-1/4 inches long. The body portion is about three fourth inch long and the tail portion (breathing tube) one half inch long. These maggots are white-colored with the body portion an elongated, oval, cylindrical shape, which is wrinkled and semitransparent, protracting into a long breathing tube (tail).
These larvae of the Syrphid fly live in highly polluted water such as livestock lagoons, polluted abandoned fish pools, foul pools and streams associated with barnyards, etc. Maggots are able to live in the water, if sufficient solids are present as food. The adult flies resemble honey bees in appearance and are often seen "hovering" near the ground in the barnyard vicinity. These flies do not bite or sting humans, and are considered beneficial because they are predaceous on aphids, etc.
Non-chemical treatment-Since this maggot breeds and feeds in highly polluted water, effort must be made to keep the lagoon in the optimum condition, promoting a more nearly ideal anaerobic condition. Usually the lagoon becomes "out-of-balance" with the water level not in proper relationship with the solids. Never allow accumulations of manure above the water line, either floating or sticking to the sides, because these conditions enhance fly development. Keep the banks steep and weeds under control.
Use loose soil and construct a soil barrier between the milk house and the rattailed maggot source. As maggots migrate to the soil barrier, they will dig into it to pupate rather than move into the milk house.
Try to agitate the pit contents frequently during the spring and summer by pumping the pits routinely (at least once a week) to disrupt maggot development. Always maintain a waterline above the manure solids. Clean out the pit contents on a routine basis, if practical.
Usually the occurrence of rattailed maggots is a management problem directly related to improper care of the lagoon or a poorly constructed lagoon. The Environmental Protection Agency (EPA) is presently very concerned with runoff and overflow leading to pollution. It is very important to coordinate with agricultural designers and Health Department officials before constructing new liquid manure tanks and lagoons. Plans are available from these agencies for constructing tanks to prevent manure seepage and polluted waters, thereby avoiding a rattailed maggot problem.
Chemical treatment-Unfortunately, there are no good pesticide control measures. There has been some success by layering either Ravap or Larvadex larvicide on the liquid and manure surface in the pits. Mix one pint of Ravap 23.0 percent per 3.5 gallons of fuel oil. Apply one gallon of prepared spray solution per 100 square feet of manure pit surface. Repeat as needed, but not more often than once every seven to ten days. Also, one can mix one quart of cyromazine (Larvadex) five percent SC per 25 gallons of water and apply one half to one gallon of prepared spray per 100 square feet of pit surface. (Do not agitate the pit contents after application for best results.) The pesticide in the fuel oil will clog up the long breathing tube of the rattailed maggot in the manure pit similar to oils applied to the surface of stagnant, non-moving water to kill mosquito larvae.