Potential selective herbicides for kyllinga (Cyperus brevifolius Rottb.) in irrigated pastures
F.L.F HenskensA and K.O. FallowB
A Agriculture Victoria, Institute of Sustainable Irrigated Agriculture, RMB 3010, Kyabram 3620, Australia. Present address: Agriculture Victoria, Institute for Integrated Agricultural Development, RMB 1145, Rutherglen 3685, Australia.
B Monsanto Australia Limited, PO Box 156, Golden Square, Bendigo 3555, Australia.
Summary
This paper reports on field assessments of the potential of halosulfuron-methyl and imazethapyr to selectively control kyllinga in irrigated pastures. Halosulfuron-methyl applied at rates of 50 and 97.5 g a.i. ha-1, and imazethapyr at 192 g a.i. ha-1significantly suppressed kyllinga as a proportion of sward DM for more than one year after application. In April 1996 kyllinga accounted for around 26% of harvested DM in untreated plots, but only 1-10% in sprayed plots. Increasing rates of halosulfuron-methyl above 50 g a.i. ha-1 did not improve efficacy. Neither herbicide appeared to suppress white clover and perennial ryegrass or have an impact on other weed species. Seed was an important source of kyllinga re-infestation. Any effective control agent must, therefore, reduce seed production. All rates of halosulfuron-methyl suppressed seed head formation, but imazethapyr did not. Consequently, halosulfuron-methyl has the greater potential for selective control of kyllinga. Other weed management tools need to be investigated as halosulfuron-methyl is not registered for use in pasture.
Plant Protection Quarterly (1998) 13 (1) 25-28.