Risk assessments of weed seeds on imported fresh produce

Abstract

Fresh fruit such as pineapples imported into New Zealand sometimes carry seeds of exotic weeds Some of these weeds do not occur here and may if established threaten agriculture or the natural environment To assist MAF in determining permissible infestation levels the risk posed to agriculture and the environment by 12 species of weeds whose seeds occur on imported fruit was assessed Most of these species are serious weeds in tropical and subtropical areas and could probably survive in New Zealand although their distribution and adverse effects may be limited The species that are considered most likely to be serious weeds at least in Northland are Chromolaena odorata a competitive fastgrowing shrub; the aggressive and weedy perennial grasses Brachiaria mutica Paspalum conjugatum and Saccharum spontaneum; the annual grass Rhynchelytrum roseum; and the free seeding annual herb Ageratum conyzoides The other species seem to pose less of a threat