Records of the distribution and control of the shrubby weed Mimosa pig
ra in wetlands within, and adjacent to, Kakadu National Park (KNP), no
rthern Australia, were examined to determine the effects of habitat va
riation and distance from large stands on the density and persistence
of the satellite outbreaks. The cumulative density of outbreaks decrea
sed with distance from the large stands to the east and west of KNP Th
ere was, however, no trend in the number of new outbreaks discovered e
ach year from 1984 until 1993, despite the doubling in area of the lar
ge stand of M. pigra to the east of KNP every 1.4 yr from the early 19
80s until 1991. The highest densities of outbreaks of M. pigra in KNP
were found in the wetland margins that had been disturbed by feral ani
mals, and in wetland habitats with a relatively long period of inundat
ion, but where trees were absent. The dispersal gradient provided a us
eful model for predicting the occurrence of outbreaks on wetlands to t
he east of KNP that had not previously been surveyed systematically. M
ore than 20% of outbreaks required sustained control for 7 yr or more
because of the establishment of plants from the persistent seedbank. T
he control of satellite outbreaks of M. pigra has successfully prevent
ed large stands developing in KNP. Detailed record-keeping by the cont
rol program has facilitated essential follow-up control and enabled th
e analysis of the spread of M. pigra, which should contribute to its e
fficient control elsewhere.