Rutherglen bug (Nysius vinitor) and grey cluster bug (Nysius clevelandensis) are native species that can migrate into crops in very large numbers in favourable seasons. Rutherglen bug is a pest of many crops across Australia, while the grey cluster bug is only a pest in Queensland and northern New South Wales.
Both species breed on a wide range of native and weed hosts, building up to large numbers in inland areas when winter and spring rainfall allows the growth of native herbs and weeds. In spring, as the hosts start to dry off, large numbers of adult bugs will move into the eastern cropping areas, migrating on the winds associated with storm fronts.
Rutherglen bug - Nysius vinitor. Grey cluster bug - Nysius clevelandensis
Adults are 3-4 mm long, mottled grey-brown-black, and have clear wings folded flat over the back. Nymphs are wingless, with a reddish-brown, pear-shaped body. N. clevelandesis and N. vinitor can be distinguished from each other with a hand lens or microscope. N. vinitor looks smooth, while N. clevelandensis is hairy.
The Rutherglen bug is common in New South Wales, Queensland, South Australia, Victoria and southern Western Australia.
The grey cluster bug is common in northern New South Wales and Queensland.
Sunflower, sorghum, canola and safflower.
Rutherglen bug has eight generations a year. In spring and summer, development from egg to adult takes 3-4 weeks. Adults will live up to four weeks, and females will lay up to 400 eggs in this period. Populations of Rutherglen bug (RGB) in cropping areas will breed on weeds, moving to available crops or weeds when hosts die off. Adults will overwinter, moving to available weeds and crops in spring and starting to breed. In seasons when RGB is a major pest, the population is dominated by migrants from outside the local cropping areas which are carried from inland breeding sites to eastern cropping regions.
Sunflower: infestation during grain set and grain fill will reduce yield, oil content and oil quality. In seed crops, RGB will reduce germination of seed. Heavy infestations during budding may cause heads to wild and distort. RGB impact is greater in moisture-stressed crops.
Sunflower and other oilseeds: from budding onwards.
Sorghum: from head emergence to physiological maturity (black layer).
Local management will have little impact on RGB in seasons when there are major influxes of bugs from outside the cropping region in spring. Managing weeds in and around paddocks prior to sowing can reduce the likelihood of bugs moving from dying weeds onto emerging seedlings.
|Conservation of natural enemies|
Egg parasitoids are the most commonly recorded natural enemy of RGB. Their potential contribution to population control will be limited in seasons when there are large influxes of adults. Predation has rarely been recorded, but spiders may play a role.