In early 2020 two thoroughbred horse studs in northern VIC reported cases of severe photosensitisation associated with grazing horses on lucerne or lucerne mix pastures in Autumn 2020. This photosensitisation may be due to an outbreak of cowpea aphid on the lucerne pastures. However, it is not yet known if it was due to the ingestion of the cowpea aphid itself or the ingestion of the cowpea aphid infested lucerne. There was no foetal loss associated with the infestation, however there was concern around possible foetal loss due to stabling and treatment of the photosensitisation.
This fact sheet aims to help breeders identify and manage cowpea aphid and take appropriate measures to avoid photosensitisation in grazing horses.