Elephants in a visiting circus may have been indirectly responsible for a recent outbreak of alligator weed, a pest plant, near Hamilton.
Waikato Regional Council said a spray contractor identified a four hectare outbreak of the weed on the outskirts of the city in April.
Council biosecurity staff found out from discussions with the landowner that it started sprouting after a load of elephant dung was purchased as fertiliser from a circus that visited Hamilton in 2007.
The possibility that the weed came from elephant dung was firmed up when it was also found in the spot where a neighbour had used some of the dung in a vegetable garden and on a lawn where the dung had been placed, before going on the garden.
Alligator weed is regarded as a dangerous pest plant because it can spread rapidly, taking over pasture, crowding out native plants and choking waterways.
The regional council has highlighted the case to coincide with biosecurity month.