Please note-these are worms and not “bots” which are the larvae of the gastrophilus fly. Gastrophilus lays eggs which resemble grass seeds. Those laid near the mouth will hatch and penetrate the mucous membranes while those laid on the legs or trunks are licked orrubbed off by the horse. They eventually migrate to the stomach via the pharynx. These larvae are what we commonly refer to as bots. When selecting a “dewormer’ it is important to know if it also kills bots. The eggs can be removed with a bot egg removing “knife” or inactivated by washing the horse in a mild acidic solution such as vinegar or soda water.
Control of flies depends on the elimination of the breeding site/s. Manure must be picked up regularly and removed from the premises or correctly composted.
Care must be taken to keep areas where moisture might accumulate, dry -i.e. around water troughs; where stables are sluiced.
There are biological methods of control such as the release of parasitic wasps which prey on the fly larvae.
The presence of flies can be minimised by the use of screens, fans, traps and sticky papers.
Insecticides can be used on ceilings, walls etc but great care must be taken to avoid licking by horses or contamination of feed and water.
The horse can be made more comfortable by the use of fly sheets, masks or fringes but these do not reduce the number of flies.