Anderson, Kylie Lucille (2011) Invasion potential of the island sugarcane planthopper, Eumetopina flavipes (Hemiptera: Delphacidae): vector of Ramu stunt disease of sugarcane. PhD thesis, James Cook University.

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Abstract

The island sugarcane planthopper, Eumetopina flavipes Muir (Hemiptera: Delphacidae) is the only known vector for Ramu stunt disease of sugarcane. Ramu stunt disease appears confined to PNG, but disease-free populations of E. flavipes are known to occur throughout the Torres Strait island archipelago and on the northern peninsula area of Cape York, Queensland, Australia. The presence of these populations represents a significant threat to the commercial production of sugarcane in Australia, which occurs approximately 700 km south of the E. flavipes populations on the northern peninsula area of Cape York, Queensland.

In order to mitigate the risk of E. flavipes and/or Ramu stunt disease invasion into Australia through the Torres Strait, and to contribute to the development of a management program for E. flavipes populations in the Torres Strait, there is a need for a detailed understanding of the mechanisms which drive E. flavipes invasion success in the Torres Strait.

Anthropogenic movement of infested sugarcane was hypothesised to be important for initial dispersal into, as well as recolonisation of populations throughout the Torres Strait. The ability of mobile life stages of E. flavipes to survive over time on cut sugarcane stalks was assessed. Whilst nymphs and adults leave the stalk at different rates over time, almost half of the initial population of nymphs and almost one third of the adults survived six days in-situ on cut stalks. E. flavipes is therefore capable of surviving extended periods of time on deteriorating host plant material, implying that human mediated movement of cut stalks may play an important role in the dispersal of E. flavipes.

In addition to the anthropogenic movement of infested sugarcane, long-distance, wind-assisted immigration from Papua New Guinea may be responsible for the continued presence of E. flavipes in the Torres Strait and on the tip of north Queensland. Simulation was used to predict E. flavipes wind-assisted immigration potential from Papua New Guinea into the Torres Strait islands and mainland Australia. Field studies were used to test the predictions. Wind-assisted immigration from Papua New Guinea was predicted to occur widely throughout the Torres Strait islands and the tip of mainland Australia, especially in the presence of tropical depressions and cyclones.

Simulation showed potential for a definite, seasonal immigration which reflected variation in the onset, length and cessation of the summer monsoon. In general, simulation predictions did not explain E. flavipes observed infestations. The discrepancy suggests that post-colonisation processes such as the temporal and spatial availability of host may be equally or more important than possible wind-assisted immigration in determining population establishment, persistence and viability.

For phytophagous insects like E. flavipes, the distribution and abundance of host plants is highly important in regulating establishment, growth and population persistence. The relationship between host plant distribution and abundance, and E. flavipes distribution, abundance and levels of population connectivity in the native range Papua New Guinea, and the introduced region of the Torres Strait and northern peninsula area of Cape York, was established. E. flavipes uses a wide range of Saccharum host species in Papua New Guinea, and occupancy rates and abundances differ significantly among host types. For hosts in common to both Papua New Guinea and Torres Strait, the proportion of plants occupied in Papua New Guinea was significantly greater than in Torres Strait. This is likely to be the result of greater overall host plant density and connectivity in Papua New Guinea. E. flavipes abundance per plant did not differ significantly between the two regions suggesting a possible plantspecific abundance and/or dispersal threshold independent of location. Whilst E. flavipes presence and persistence was highly variable at some Torres Strait locations, large and stable infestations occurred along the western edge of the Torres Strait archipelago. These populations appear to link Papua New Guinea to the northern peninsula area, and offer a potential incursion route for Ramu stunt disease. The stability of these populations appears to be associated with the availability and persistence of host plants, which in turn is significantly affected by location-specific variations in cultivation practices.

Information on hypothesised dispersal mechanisms was combined with analyses of population genetic structure to investigate the invasion dynamics of E. flavipes through the Torres Strait. Analysis of data from eight microsatellites in 648 individuals suggest that frequent, wind-assisted immigration from multiple sources in Papua New Guinea contributes significantly to repeated colonisation of Torres Strait islands close to Papua New Guinea. In contrast, intermittent long-distance, wind assisted immigration better explains patterns of genetic diversity and structure in the southern Torres Strait and on the tip of mainland Australia. Significant genetic structuring associated with the presence of clusters of highly related individuals occurs throughout the region. In general, this suggests that following colonisation by small numbers of individuals, population growth on each island is kin-structured with little post-establishment movement. There is some evidence that secondary movements between islands are restricted by quarantine zones. Control of the planthopper may be very difficult on islands close to Papua New Guinea given the propensity.

Results suggest that implementation of pre-emptive management of E. flavipes via particular cultivation techniques, such as the simultaneous tip-pruning of all sugarcane plants in the area, may be an effective means of control and/or eradication for the pest in parts of the Torres Strait. Eradication of E. flavipes from northern Torres Strait islands appears unlikely given the propensity for annual invasion, but may be achievable further south where local populations appear highly independent and isolated.

The creation of a planthopper-free buffer zone in the southern Torres Strait would serve to reduce the invasion threat to commercial Australian sugarcane. Pre-emptive management of E. flavipes in the Torres Strait islands and on the northern peninsula area of Cape York, Australia, is thus recommended using the strategy outlined in this thesis. Pre-emptive management of E. flavipes would be simpler and preferable to the direct management of Ramu stunt disease should it be detected in the Torres Strait.

Item ID:	23729
Item Type:	Thesis (PhD)
Keywords:	Cape York, colonisation, colonization, disease vectors, Eumetopina flavipes, extinction, insect pests, invasion ecology, island ecology, long-distance dispersal, migration, Papua New Guinea, plant hoppers, planthoppers, population genetics, Ramu stunt disease, sugar cane, sugarcane, Torres Strait
Related URLs:	http://eprints.jcu.edu.au/3055/ http://eprints.jcu.edu.au/16276/ http://eprints.jcu.edu.au/5506/
Additional Information:	Publications arising from this thesis are available from the Related URLs field. The publications are: Chapter 2: Anderson, Kylie K., Sallam, Mohamed, and Congdon, Bradley C. (2007) Long distance dispersal by Eumetopina flavipes (Hemiptera: Delphacidae), vector of Ramu stunt: is culture contributing? In: Proceedings of the 2007 Conference Australian Society of Sugar Cane Technologists. 29th Conference of the Australian Society of Sugar Cane Technologists, 8-11 May 2007, Cairns, Queensland. Chapter 3: Anderson, Kylie L., Deveson, Ted E., Sallam, Nader, and Congdon, Bradley C. (2010) Wind-assisted migration potential of the island sugarcane planthopper Eumetopina flavipes (Hemiptera: Delphacidae): implications for managing incursions across an Australian quarantine frontline. Journal of Applied Ecology, 47 (6). pp. 1310-1319. Chapter 4: Anderson, Kylie L., Sallam, Nader, and Congdon, Bradley C. (2009) The effect of host structure on the distribution and abundance of the island sugarcane planthopper, Eumetopina flavipes Muir, vector of Ramu stunt disease of sugarcane. Virus Research, 141 (2). pp. 247-257.
Date Deposited:	23 Oct 2012 04:48
FoR Codes:	07 AGRICULTURAL AND VETERINARY SCIENCES > 0703 Crop and Pasture Production > 070308 Crop and Pasture Protection (Pests, Diseases and Weeds) @ 33% 06 BIOLOGICAL SCIENCES > 0602 Ecology > 060207 Population Ecology @ 33% 05 ENVIRONMENTAL SCIENCES > 0501 Ecological Applications > 050103 Invasive Species Ecology @ 34%
SEO Codes:	82 PLANT PRODUCTION AND PLANT PRIMARY PRODUCTS > 8203 Industrial Crops > 820304 Sugar @ 33% 96 ENVIRONMENT > 9604 Control of Pests, Diseases and Exotic Species > 960413 Control of Plant Pests, Diseases and Exotic Species in Farmland, Arable Cropland and Permanent Cropland @ 34% 82 PLANT PRODUCTION AND PLANT PRIMARY PRODUCTS > 8206 Harvesting and Packing of Plant Products > 820603 Sugar Cane (Cut for Crushing) @ 33%
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