Biological control of serrated tussock and Chilean needlegrass
F. AndersonA, W. PettitB, D.T. BrieseB and D.A. McLarenC
A Departamento de Agronomía, Universidad Nacional del Sur, Altos de Palihue, 8000 Bahía Blanca, Argentina.
B CRC for Australian Weed Management, CSIRO Entomology, GPO Box 1700, Canberra, ACT 2601, Australia.
C CRC for Australian Weed Management, Department of Natural Resources and Environment, Keith Turnbull Research Institute, Frankston, Victoria 3199, Australia.
Surveys of pathogens attacking N. trichotoma and N. neesiana in South America have identified three pathogens showing potential for biological control. These are a rust, Puccinia nassellae, a smut, Ustilago sp. and a Corticiaceae basidiomycete fungus. Different strains of the P. nassellae have been found attacking N. trichotoma and N. neesiana. Differencesin life cycle and host range indicate that these strains should be treated separately. P. nassellae attacking N. trichotoma has not attacked N. neesiana and vice versa. However, preliminary host specificity testing of P. nassellae attacking N. trichotoma has shown some low level infection of the Australian native grass, Austrostipa aristoglumis.
Field observations suggest that the rust on N. trichotoma may be autoecious, but as no telia spores have been found, it is not possible to prove the nature of the life cycle on the host. Its impact appears highly dependent on environmental conditions and this will reduce its effectiveness as a biological control agent in drier locations. To date, P. nassellae attacking N. neesiana has been host specific, less dependent on environmental conditions for attack and its entire life cycle occurs on N. neesiana. Ustilago sp. can cause significant reductions in seed production but its incidence in South America is relatively low. Host specificity of Ustilago sp is still under investigation but it is known that the Ustilago sp. that infects N. trichotoma also infects other Nassella species. A Corticiaceae fungus that attacks the crowns and roots of N. trichotoma has been identified at a few isolated locations. Little is known of its life cycle or host specificity at this stage. Concerns over agent host specificity and effectiveness in weed control are raised.
Plant Protection Quarterly (2002) 17 (3) 104-111.