WEED SEED SPREAD BY VEHICLES: A CASE STUDY FROM SOUTHEAST QUEENSLAND, AUSTRALIA

Weed seed spread, from infested to uninfested areas, is by a number of biotic and abiotic mechanisms, and this spread of seed aids the invasion process across the landscape. Currently in Queensland there are approximately 3.2 million motorized vehicles, each capable of carrying, and therefore spreading, weed seeds. Studies were conducted in 2009/10 to investigate the role of the utility vehicle in the spread of weed seeds in south east Queensland. A large number (209) of viable seed were found on vehicles and in each of the four seasons of the year. The largest number seeds per vehicle were collected in the autumn (48%) and the lowest number in the winter (14%). These viable seeds were found on a number of parts of the vehicles and were contained within mud or dust that had presumable transferred on to the vehicle as it undertook its routine activities. The highest percentages of seed were collected from the underside of the vehicle (36%), followed by back mudguards (24%), front mudguard (16%) and cabin (12%). Lower percentages were found on engine, radiator (3%) and tyres and rims(9%). The seeds found on the vehicles belonged to 90 species, coming from 26 families. The majority of these species were alien to Australia (66%) and Queensland (73%).The early implications from this present study are that utility vehicles are capable of collecting, carrying and presumably distributing large numbers of viable weed seeds, that seed is carried on many parts of the vehicle and that this occurs in all seasons of the year. Thus, any washing or cleaning procedure used to remove weed seeds from vehicles will need to concentrate on all parts of the vehicle and that this should be done in all seasons. Cleaning vehicles at appropriate places should be seen as a possible way to reduce weed seed spread by utility vehicles.