Abstracts: Theme 3 – Target and Agent Selection

Nigrospora oryzae, a potential bio-control agent for Giant Parramatta Grass ( fertilis) in

S. Ramasamy,1,4 D. Officer,3,4 A.C. Lawrie1 and D.A. McLaren2,4 1RMIT University, Bundoora West Campus, PO Box 71, Bundoora 3083, Australia 2Department of Primary Industries, Frankston Centre, PO Box 48, Frankston 3199, Australia 3NSW Agriculture, PMB 2, Grafton NSW 2480, Australia 4CRC for Australian Weed Management, Australia.

Giant Parramatta Grass (GPG) is an aggressive perennial tussocky grass from tropical Asia that is a declared noxious weed in Australia. It invades native pastures and reduces animal production. Its po- tential distribution is estimated at 23.7 million hectares in Australia. A fungus was isolated from dead shoot tips and flag leaves ofSporobolus fertilis (Steud.)Clayton () in Australia. The fungus was identified as Nigrospora oryzae (Berk and Broome) Petch based on the morphological characteristics and fruiting bodies. Its identity was confirmed by DNA sequencing using primers ITS 1 and ITS 4 to the internal transcribed spacer (ITS) region. N. oryzae was investigated as a potential bio-control agent for GPG. Forty healthy of uniform size were selected for the experiment. Twenty plants were inoculated to run-off with spore suspension (106/ml in 0.1% Tween 20) and the control plants with Tween 20 alone. Necrosis and cessation of growth occurred in inoculated plants but not in control plants. This is the first report of N. oryzae on GPG in Australia, and further trials are warranted to test its potential as a bio-control agent for this noxious weed.

Biological control and ecology of the submerged aquatic weed Cabomba caroliniana

S.S. Schooler,1 G.C. Walsh2 and M.H. Julien3 1CSIRO Entomology, 120 Meiers Road, Indooroopilly, QLD 4068, Australia 2USDA–ARS South American Biological Control Laboratory, Bolivar 1559, Hurlingham, Buenos Aires, Argentina 3CSIRO Entomology European Laboratory, Campus International de Baillarguet, 34980 Montferrier sur Lez, France

Cabomba caroliniana is a submerged aquatic from South America that is becoming a serious weed worldwide. It spreads by seed and by fragmentation and has an extremely wide climatic range, invading lakes and ponds from tropical (Darwin, Australia: latitude 12°) to cold temperate regions (Peterborough, Canada: latitude 45°). There are currently no effective methods of managing cabomba infestations, and funding has been allocated to research biological methods. Surveys have examined cabomba in its native range and have identified several potential biological control agents. The most promising are a stem-boring weevil and two aquatic Pyralid moths. We have also examined the effects of depth and season on the dynamics of cabomba populations in Australia. We found that cabomba exhibits no clear seasonal patterns in biomass at three lakes in southeast Queensland. The plant has greatest biomass in 2–3 m depth of water (mean = 185.6 g m−2, SD = 118.8 g m−2), but rooted plants were found down to depths of 6 m. This study indicates that host plant resources will be available for biological control agents throughout the year, which is likely to result in more stable and potentially more effective biological control.

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