The influence of planting density on the production of 'Goldfinger' (Musa spp., AAAB) in the subtropics

'Goldfinger', a tetraploid banana produced from the Fundación Hondureña de Investigación Agrícola (FHIA) breeding program, was released to the Australian industry in 1995. It was promoted as an apple-flavoured dessert banana with resistance to Fusarium wilt race 1 and subtropical race 4, as well as resistance to black and yellow Sigatoka (Mycosphaerella fijiensis and M. musicola, respectively). This study was initiated to provide agronomic information to the banana industry, which was under threat from Fusarium wilt, on a new cultivar which could replace 'Williams' (AAA, Cavendish subgroup) or 'Lady Finger' (AAB, Pome subgroup) in those areas affected by Fusarium wilt. Also few studies had reported on the production characteristics of the new tetraploid hybrids, especially from subtropical areas, and therefore two field sites, one a steep-land farm and the other a level, more productive site, were selected for planting density and spatial arrangement treatments. The optimum density in terms of commercial production, taking into account bunch weight, finger size, length of the production cycle, plant height and ease of management, was 1680 plants/ha on the steep-land site where plants were planted in single rows with 2.5 m × 2.5 m spacings. However on the level site a double-row triangular layout with inter-row distances of 4.5 m to allow vehicular access (1724 plants/ha) gave the best results. With this arrangement plants were in an alternate, triangular arrangement along a row and a spacing of 1.5 m between plants at the points of each triangle and between each block of triangles.

Survival of Campylobacter spp. in darkling beetles (Alphitobius diaperinus) and their larvae in Australia

Campylobacter infection is the most frequently reported notifiable food-borne disease in humans in Australia. Our studies investigated the persistence of Campylobacter spp. in or on darkling beetles (Alphitobius diaperinus) and their larvae. Our results in analyses with chickens confirm that, unless very short turnaround times are used (<72 h), beetles colonized in one production cycle (i.e., one batch of chickens) are most unlikely to still be colonized during the next cycle of chickens.

Infection with Menangle virus in flying foxes (Pteropus spp.) in Australia

Objective: To examine flying foxes (Pteropus spp.) for evidence of infection with Menangle virus. Design: Clustered non-random sampling for serology, virus isolation and electron microscopy (EM). Procedure: Serum samples were collected from 306 Pteropus spp. in northern and eastern Australia and tested for antibodies against Menangle virus (MenV) using a virus neutralisation test (VNT). Virus isolation was attempted from tissues and faeces collected from 215 Pteropus spp. in New South Wales. Faecal samples from 68 individual Pteropus spp. and four pools of faeces were examined by transmission EM following routine negative staining and immunogold labelling. Results: Neutralising antibodies (VNT titres ≥ 8) against MenV were detected in 46% of black flying foxes (P. alecto), 41% of grey-headed flying foxes (P. poliocephalus), 25% of spectacled flying foxes (P. conspicillatus) and 1% of little red flying foxes (P. scapulatus) in Australia. Positive sera included samples collected from P. poliocephalus in a colony adjacent to a piggery that had experienced reproductive disease caused by MenV. Virus-like particles were observed by EM in faeces from Pteropus spp. and reactivity was detected in pooled faeces and urine by immunogold EM using sera from sows that had been exposed to MenV. Attempts to isolate the virus from the faeces and tissues from Pteropus spp. were unsuccessful. Conclusion: Serological evidence of infection with MenV was detected in Pteropus spp. in Australia. Although virus-like particles were detected in faeces, no viruses were isolated from faeces, urine or tissues of Pteropus spp.

Evaluating new insecticides for the control of Helicoverpa spp. (Lepidoptera: Noctuidae) on capsicum and zucchini

The efficacy of insecticides in controlling Helicoverpa spp., predominantly H. armigera (Hubner), on capsicum and zucchini was tested in small plot trials. Indoxacarb, methoxyfenozide, spinosad, emamectin benzoate and novaluron provided control, as measured by the percentage of damaged fruit, equal to or better than standard treatments of methomyl or methomyl alternated with methamidophos on capsicum. The Helicoverpa nucleopolyhedrovirus gave control equivalent to the standard treatment, as did Bacillus thuringiensis aizawai, but B. thuringiensis kurstaki was ineffective. Helicoverpa armigera larvae were present in zucchini flowers but did little damage to the fruit. None of the insecticides significantly reduced the percentage of damaged zucchini fruit compared with the untreated control. Bifenthrin, spinosad, emamectin benzoate and methoxyfenozide were effective in controlling larvae in flowers, while methomyl, B. thuringiensis aizawai, B. thuringiensis kurstaki and novaluron were not effective. Data indicated that all the insecticides effectively controlled larvae of Diaphania indica (Saunders), cucumber moth, in the zucchini flowers. There has been a limited range of insecticides available to manage Helicoverpa spp. in these vegetable crops, but these trials demonstrate the effectiveness of a number of newer insecticides that could be used and that would be compatible with integrated pest management programs in the crops.

Oidiopsis (Erysiphaceae) on Euphorbia spp. in Australia and Vanuatu

One specimen of powdery mildew on Euphorbia cyathophora from Vanuatu and 11 specimens on E. cyathophora, E. dentata, E. heterophylla and E. leucocephala from Australia were studied. All were shown to represent the Oidiopsis anamorph of Leveillula taurica, which is described. This is the first record of Oidiopsis in Vanuatu. E. leucocephala is a new host record for this powdery mildew.

Molecular characterisation, pathogenesis and fungicide sensitivity of Pythium spp. from table beet (Beta vulgaris var. vulgaris) grown in the Lockyer Valley, Queensland

Table beet production in the Lockyer Valley of south-eastern Queensland is known to be adversely affected by soilborne root disease from infection by Pythium spp. However, little is known regarding the species or genotypes that are the causal agents of both pre- and post-emergence damping off. Based on RFLP analysis with HhaI, HinfI and MboI of the PCR amplified ITS region DNA from soil and diseased plant samples, the majority of 130 Pythium isolates could be grouped into three genotypes, designated LVP A, LVP B and LVP C. These groups comprised 43, 41 and 7% of all isolates, respectively. Deoxyribonucleic acid sequence analysis of the ITS region indicated that LVP A was a strain of Pythium aphanidermatum, with greater than 99% similarity to the corresponding P. aphanidermatum sequences from the publicly accessible databases. The DNA sequences from LVP B and LVP C were most closely related to P. ultimum and P. dissotocum, respectively. Lower frequencies of other distinct isolates with unique RFLP patterns were also obtained with high levels of similarity (>97%) to P. heterothallicum, P. periplocum and genotypes of P. ultimum other than LVP B. Inoculation trials of 1- and 4-week-old beet seedlings indicated that compared with isolates of the LVP B genotype, a higher frequency of LVP A isolates caused disease. Isolates with the LVP A, LVP B and LVP C genotypes were highly sensitive to the fungicide Ridomil MZ, which suppressed radial growth on V8 agar between approximately four and thirty fold at 5 μg/mL metalaxyl and 40 μg/mL mancozeb, a concentration far lower than the recommended field application rate.

Biology and host range of Ophiomyia camarae Spencer (Diptera: Agromyzidae), a potential biocontrol agent for Lantana spp. (Verbenaceae) in Australia

The life history and host range of the herringbone leaf-mining fly Ophiomyia camarae, a potential biological control agent for Lantana spp., were investigated. Eggs were deposited singly on the underside of leaves. Although several eggs can be laid on a single leaf and a maximum of three individual mines were seen on a single leaf, only one pupa per leaf ever developed. The generation time (egg to adult) was about 38 days. Females (mean 14 days) lived longer than males (mean 9 days) and produced about 61 mines. Oviposition and larval development occurred on all five lantana phenotypes tested. Eleven plant species representing six families were tested to determine the host range. Oviposition and larval development occurred on only lantana and another nonnative plant Lippia alba (Verbenaceae), with both species supporting populations over several generations. A CLIMEX model showed that most of the coastal areas of eastern Australia south to 30°16' S (Coffs Harbour) would be suitable for O. camarae. O. camarae was approved for release in Australia in October 2007 and mines have been observed on plants at numerous field sites along the coast following releases.

Infection and disease development of Quambalaria spp. on Corymbia and Eucalyptus spp.

Quambalaria spp. are eucalypt leaf and shoot pathogens of growing global importance, yet virtually nothing is known regarding the manner in which they infect and colonize their hosts. A study of the infection process of Q. pitereka and Q.eucalypti on Corymbia and Eucalyptus species was thus undertaken using light, scanning and transmission electron microscopy after artificial inoculation. Conidial germination was triggered when relative humidity levels exceeded 90% and commenced within 2 h in the presence of free water. Light reduced germination but did not prevent germination from occurring. Conidial germination and hyphal growth occurred on the upper and lower leaf surfaces with penetration occurring via the stomata or wounds on the leaf surface or juvenile stems. There was no evidence of direct penetration of the host. Following penetration through the stomata, Q. pitereka and Q. eucalypti hyphae grew only intercellularly without the formation of haustoria or interaction apparatus, which is characteristic of the order Microstromatales. Instead, the presence of an interaction zone is demonstrated in this paper. Conidiophores arose through stomatal openings producing conidia 7 days after infection.

Ramichloridium spp. on Musa in northern Queensland: introducing Ramichloridium ducassei sp. nov. on leaf streaks of Ducasse banana.

The fungi associated with tropical leaf speckle diseases of banana (Musa spp. and cultivars) in northern Queensland were examined from fresh leaves and herbarium specimens. Ramichloridium biverticillatum was predominantly found associated with leaves of Cavendish banana (Musa acuminata cv. Cavendish) and a new species, R. ducassei was found associated with dark brown streaks on leaves of Ducasse banana (Musa acuminata x balbisiana cv. Pisang awak). A key is provided for all of the species of Ramichloridum that are known to occur on Musa.

Preliminary investigation into the induction of reproduction in Ulva spp. in Southeast Queensland for mass cultivation purposes

Ulva is a common component of marine intertidal flora in Australia with many species frequently observed along the Queensland coastline. Three species of Ulva, U. lactuca, U. intestinalis and U. prolifera were found to naturally occur at the Bribie Island Research Centre (BIRC) in Southeast Queensland. Studies were undertaken to establish the most optimal conditions for growing Ulva in the BIRC laboratory. These tests were conducted in order to condition the algal material prior to the sporulation studies, offering more controlled material to assess treatment effects conclusively, and helping eliminate other potentially confounding environmental factors. Results showed that a stocking density of between 5-20 grams of Ulva per litre along with the addition of the soluble fertiliser Aquasol at a rate of 87 mg/L of seawater was ideal for achieving a desired doubling of growth per week. In the wild the formation of Ulva fragments occurs naturally in the ocean through wave and storm action. This breakage can trigger a survival response mechanism which stimulates the algae to form and release gametes. By chopping the tissue, this process could be artificially simulated in the laboratory and creating a simple and easy way to produce new individuals. Studies performed into inducing sporulation in Ulva through a combination of fragmentation and renewal of medium at BIRC showed that sporulation can be successfully induced in all three species of Ulva through these methods, however it was found to be to a degree that would not meet the demands of commercial production with on average a rate of only 33% achieved. While the current study did not find a method suitable for a commercial application the results presented here contribute to increasing our understanding about Ulva reproduction and set a platform for future work in to cultivating Ulva within Southeast Queensland.

Background to the approved beneficial Cynodon spp. vegetative cultivars within Australia

The growth of the Australian turfgrass industry has significantly expanded over recent decades. One reason for this occurring has been with development of better suited or higher quality turfgrass cultivars for Australia’s harsh climatic conditions. In recent years drought has widely affected the turfgrass industry and as such, greater drought tolerant C4 grasses such as Cynodon spp. have been used. In 2008, as part of the 24th Australian Turfgrass Conference Proceedings, Peter McMaugh wrote an extensive article on the couch grass breeding history in Australia. This paper contains an extension to his work detailing the current (1950s to 2010) Cynodon species found in Australia. Detailed information has been sourced in relation to the origin and development of the grasses which are suitable for turfgrass use. Such detail provides an interesting picture of the source of proliferation of newer cultivars and how the Australian industry has evolved with the introduction of overseas and Australian selected cultivars. The information adds to the preceding work, including morphological and agronomic attributes and how closely each selection or cultivar is related. The cultivars discussed in this article (listed alphabetically) are derived from one of the four classifications identified by the breeder/author, being (i) Cynodon sp. (although the cultivar contained within the taxa fits best being classified as a Cynodon hybrid), (ii) Cynodon dactylon x C. transvaalensis (Cynodon hybrid), (iii) Cynodon dactylon (green couch) and (iv) Cynodon dactylon x C. magenissii.

Effects of climate change on reproduction,larval development, and adult health of coral trout (Plectropomus spp.)

Climate change is emerging as the single greatest threat to coral-reef ecosystems.The most immediate impacts will be a loss of diversity and changes to fish community composition and may lead to eventual declines in abundance and productivity of key fisheries species. A key component of this research is to assess effects of projected changes in environmental conditions (temperature and ocean acidity) due to climate change on reproduction, growth and development of coral trout (Plectropomus leopardis).Ultimately, this research will fill key knowledge gaps about climate change impacts on larger fishes, which are fundamental to optimizing resilience-based management, and in turn improve the adaptive capacity of industries and communities along the Great Barrier Reef.

Life history and host range of Alagoasa extrema (Coleoptera: Chrysomelidae: Alticinae), a potential biological control agent of Lantana spp. (Verbenaceae) in Australia

The life history and host range of the lantana beetle, Alagoasa extrema, a potential biocontrol agent for Lantana spp. were investigated in a quarantine unit at the Alan Fletcher Research Station, Brisbane, Australia. Adults feed on leaves and females lay batches of about 17 eggs on the soil surface around the stems of plants. The eggs take 16 days to hatch and newly emerged larvae move up the stem to feed on young leaves. Larvae feed for about 23 days and there are three instars. There is a prepupal non-feeding stage that lasts about 12 days and the pupal stage, which occurs in a cocoon in the soil, lasts 16 days. Teneral adults remain in the cocoon for 3 days to harden prior to emergence. Males live for about 151 days while females live for about 127 days. The pre-oviposition period is 19 days. In no-choice larval feeding trials, nine plant species, representing three families, supported development to adult. Three species, Aloysia triphylla, Citharexylum spinosum and Pandorea pandorana were able to support at least two successive generations. These results confirm those reported in South Africa and suggest that A. extrema is not sufficiently specific for release in Australia. Furthermore, it is not recommended for release in any other country which is considering biological control of lantana.

Hybridisation of Australian chickpea cultivars with wild Cicer spp. increases resistance to root-lesion nematodes (Pratylenchus thornei and P. neglectus).

Australian and international chickpea (Cicer arietinum) cultivars and germplasm accessions, and wild annual Cicer spp. in the primary and secondary gene pools, were assessed in glasshouse experiments for levels of resistance to the root-lesion nematodes Pratylenchus thornei and P. neglectus. Lines were grown in replicated experiments in pasteurised soil inoculated with a pure culture of either P. thornei or P. neglectus and the population density of the nematodes in the soil plus roots after 16 weeks growth was used as a measure of resistance. Combined statistical analyses of experiments (nine for P. thornei and four for P. neglectus) were conducted and genotypes were assessed using best linear unbiased predictions. Australian and international chickpea cultivars possessed a similar range of susceptibilities through to partial resistance. Wild relatives from both the primary (C. reticulatum and C. echinospermum) and secondary (C. bijugum) gene pools of chickpea were generally more resistant than commercial chickpea cultivars to either P. thornei or P. neglectus or both. Wild relatives of chickpea have probably evolved to have resistance to endemic root-lesion nematodes whereas modern chickpea cultivars constitute a narrower gene pool with respect to nematode resistance. Resistant accessions of C. reticulatum and C. echinospermum were crossed and topcrossed with desi chickpea cultivars and resistant F(4) lines were obtained. Development of commercial cultivars with the high levels of resistance to P. thornei and P. neglectus in these hybrids will be most valuable for areas of the Australian grain region and other parts of the world where alternating chickpea and wheat crops are the preferred rotation.

Burning, then resting, reduces wiregrass (Aristida spp.) in black speargrass pastures

Wiregrasses (Aristida spp.) are becoming more prevalent, causing reduced productivity, in the black speargrass (Heterpogon contortus) pastures of south-east Queensland. Burning a native pasture of poor botanical composition (with a high proportion of wiregrass) in spring, and resting a heavily-grazed pasture also of poor composition, both improved the condition of these pastures. However, burning in late summer did not. Three months after burning in spring, relative density of wiregrass had decreased and that of a desirable species, black speargrass, had increased. However, this effect did not persist under continuous and heavy grazing. Resting increased threefold both the yield of pasture and the proportion of black speargrass, and decreased the proportion of wiregrass by two-thirds. Burning in late summer had no effect on the relative density of black speargrass but relative density of wiregrass increased. Selective grazing after burning in late summer kept this pasture in very poor condition for 14 months. These results suggest that the best way to increase the proportion of black speargrass and reduce the proportion of wiregrass in a pasture would be to burn in spring and then rest the pasture