Feeding by Nysius natalensis (Hemiptera: Orsillidae) adults on sunflower heads reduces grain yield, oil content and seed germination. Since the insect is known to feed on several host plants, a study was conducted on its host plant range to assess the role that weeds played in the pest status of this insect throughout the sunflower production area of South Africa. Roadside surveys of hosts, conducted in every quarter-degree grid of the sunflower production area, showed that N. natalensis was ubiquitous. The insect survived, developed and reproduced across a wide range of temperature and rainfall conditions. Feeding of nymphs and adults, as well as the presence of eggs was observed on 26 plant species belonging to eight families. The polyphagous habits of N. natalensis, together with a favourable temperature range for development in its distribution area, are important factors in determining population density of the pest. Late-planted sunflowers were prone to N. natalensis damage because seed-fill coincided with high numbers of the insect that increased during spring and summer. These individuals migrated onto sunflower with senescence of host weeds prior to winter. Recommendations are made on weed management practices to limit damage by N. natalensis.