Landscape factors and how they influence whitefly pests in cassava fields across East Africa     

Macfadyen  Sarina  Tay  Wee Tek  Hulthen  Andrew D.  Paull  Cate  Kalyebi  Andrew  Jacomb  Frances  Parry  Hazel  Sseruwagi  Peter  Seguni  Zuberi  Omongo  Christopher Abu  Kachigamba  Donald  Otim  Michael  Schellhorn  Nancy  Polaszek  Andrew  Colvin  John  De Barro  Paul 《Landscape Ecology》2021,36(1):45-67

Context

African production landscapes are diverse, with multiple cassava cultivars grown in small patches amongst a diversity of other crops. Studies on how diverse smallholder landscapes impact herbivore pest outbreak risk have not been carried out in sub-Saharan Africa.

Objectives

Bemisia tabaci is a cryptic pest species complex that cause damage to cassava through feeding and vectoring plant-virus diseases and are known to reach very high densities in certain contexts. However, the factors driving this phenomenon are unclear.

Methods

Bemisia density data in cassava across a large number of sites representing a geographic gradient across Uganda, Tanzania and Malawi were collected. We tested whether in-field or landscape factors associated with land-use patterns underpinned Bemisia density variability and parasitism.

Results

We found the B. tabaci SSA1 species dominated our study sites, although other species were also common in some cassava fields. Factors associated with the surrounding landscape were unimportant for explaining variability in adult density, but the in-field variables of cassava age and cultivar were very important. The density of nymphs and the parasitism of nymphs was heavily influenced by a diversity of landscape factors surrounding the field, including the size of focal cassava field, and area of cassava in the landscape. However, unlike the trend from many other studies on drivers of natural enemy populations, this pattern was not solely related to the amount of non-crop vegetation, or the diversity of crops grown in the landscape.

Conclusions

Our findings provide management options to reduce whitefly abundance, including describing the characteristics of landscapes with high parasitism. The choice of cassava cultivar by the farmer is critical to reduce whitefly outbreak risk at the landscape-scale.

  相似文献   

Spatial analysis of seroconversion of sentinel cattle to bluetongue viruses in Queensland     

MP WARD  TE CARPENTER  SJ JOHNSON 《Australian veterinary journal》1996,74(2):128-131

Objective To assess quantitatively the spatial distribution of seroconversion of Queensland cattle to bluetongue viruses.
Design A sentinel herd study. Sample population Sixty-nine sentinel herds at 30 locations.
Procedure Spatial clustering of seroconversion to blue-tongue viruses was investigated during the period from 1990 to 1994.
Results Seroconversion to only two bluetongue virus serotypes, 1 and 21, was observed. The 14 herds, in which seroconversion to bluetongue virus serotype 1 was detected, were located only along the eastern coastal and subcoastal region of Queensland, and were significantly (P < 0.05) clustered. Locations at which seroconversion to serotype 21 was detected, were not significantly clustered. The results generally agree with field observations, except for the failure to detect seroconversion to bluetongue viruses in north-western Queensland.
Conclusion Bluetongue infection of cattle in north-western Queensland may be temporally sporadic. The dominance of serotype 1 in the Queensland cattle population may be the result of differential transmission by potential vector species. Long-term surveillance programs are important for defining disease status of animal populations.  相似文献   

Reply     

SJ JOHNSON 《Australian veterinary journal》1992,69(3):70-70

  相似文献   

Pesticide residues in foodstuffs in Great Britain. XV.—Triphenyltin residues in potatoes     

B. Thomas  Hazel L. Tann 《Pest management science》1971,2(1):45-47

An analytical method and results are given for the determination of triphenyltin residues in potatoes. Of the 44 samples analysed 35 contained residues of 0.001 ppm or less; residues in 6 of the samples were in the range 0.002–0.005 ppm and in 3 samples in the range 0.006–0.008 ppm.  相似文献   

Did transmission of Helicobacter pylori from humans cause a disease outbreak in a colony of Stripe-faced Dunnarts (Sminthopsis macroura)?     

Every AL  Selwood L  Castano-Rodriguez N  Lu W  Windsor HM  Wee JL  Swierczak A  Marshall BJ  Kaakoush NO  Mitchell HM  Sutton P 《Veterinary research》2011,42(1):26

ABSTRACT: Since the discovery that Helicobacter pylori causes a range of pathologies in the stomachs of infected humans, it has become apparent that Helicobacters are found in a diverse range of animal species where they are frequently associated with disease. In 2003 and 2004, there were two outbreaks of increased mortality associated with gastric bleeding and weight-loss in a captive colony of the Australian marsupial, the Stripe-faced Dunnart (Sminthopsis macroura). The presence of gastric pathology led to an investigation of potential Helicobacter pathogenesis in these animals. Histological examination revealed the presence of gastritis, and PCR analysis confirmed the presence of Helicobacter infection in the stomachs of these marsupials. Surprisingly, sequencing of 16S rRNA from these bacteria identified the species as H. pylori and PCR confirmed the strain to be positive for the important pathogenesis factor, cagA. We therefore describe, for the first time, an apparent reverse zoonotic infection of Stripe-faced Dunnarts with H. pylori. Already prone to pathological effects of stress (as experienced during breeding season), concomitant H. pylori infection appears to be a possible essential but not sufficient co-factor in prototypic gastric bleeding and weight loss in these marsupials. The Stripe-faced Dunnart could represent a new model for investigating Helicobacter-driven gastric pathology. Infections from their human handlers, specifically of H. pylori, may be a potential risk to captive colonies of marsupials.  相似文献   

Critiquing pro‐poor tourism – By Scheyvens Regina     

Hazel Tucker 《Asia Pacific viewpoint》2011,52(3):379-380

  相似文献   

An outbreak of tuberculosis affecting cattle and people on an Irish dairy farm,following the consumption of raw milk     

Doran P  Carson J  Costello E  More S 《Irish veterinary journal》2009,62(6):390-397

Bovine tuberculosis is an ongoing problem in Ireland, and herd incidence has remained at approximately 5% for some years. Spillover of infection from cattle to people remains an ever-present possibility, given the ongoing pool of infection in the Irish cattle population. This paper describes an outbreak of tuberculosis affecting cattle and people on a dairy farm in southeastern Ireland following the consumption of milk from a seven-year-old cow with tuberculous mastitis. Twenty-five of 28 calves born during autumn 2004 and spring 2005 were subsequently identified as TB reactors, and five of six family members were positive on the Mantoux test. During 2005, milk from this cow had mainly been used to feed calves, and was added only occasionally to the bulk tank. Therefore, the calves each received infected milk on an almost continuous basis between birth and weaning. The family collected milk from the bulk milk tank, and consumed it without pasteurisation. This case highlights the risks associated with the consumption of raw milk. In this family, TB has had a very significant impact on the health of two young children. These risks are well recognised, and relevant information for farmers is available. It is of concern, therefore, that raw milk consumption remains prevalent on Irish farms. New strategies are needed, in partnership with industry, to address this important issue. Keywords: bovine tuberculosis, Ireland, mastitis, milk, Mycobacterium bovis, pasteurisation, TB, zoonosis.  相似文献   

An evaluation of Irish cattle herds with inconclusive serological evidence of bovine brucellosis     

Hayes M  Ashe S  Collins D  Power S  Kenny K  Sheahan M  O'Hagan G  More S 《Irish veterinary journal》2009,62(3):182-190

Since 1998, there has been a steady decline in herd restrictions and de-populations in Ireland due to bovine brucellosis. There is concern that the interpretation of laboratory results may become increasingly problematic, as brucellosis prevalence falls in Ireland. Therefore, the purpose of the current study was to evaluate the infection status of Irish herds and animals with inconclusive serological evidence of bovine brucellosis. During 12 months from September 1, 2004, laboratory and observational epidemiological data were collected from all Irish herds where animal testing identified at least one animal with a complement fixation test (CFT) reading greater than zero and/or a positive result to the indirect enzyme-linked immunosorbent assay (iELISA). Due to the observational nature of the study, we have robust estimates of the relative, but not the absolute, performance of the CFT, iELISA and brucellin skin test (BST). Herds were divided into three categories (Group A, B or C) on the basis of test results at initial assessment. A total of 639 herds were enrolled into the study, and observed for at least two years following enrolment. A rising CFT titre, with a CFT reading of 111 International CFT Units (IU) or greater at the subsequent blood test, was generally associated with herds where other evidence of infection was also available. Knowledge of the CFT reading at the initial and a subsequent blood test proved useful in distinguishing false-positive and true-positive brucellosis results. There was poor correlation between the CFT and iELISA results, and between the CFT and BST results. As a result of this study, national policy has been modified to include re-sampling of all animals with CFT readings of 20 IU or greater. This project has also led to a reduction in the number of herds restricted, as well as restriction duration. It has also contributed to a reduction in the number of herds listed for contiguous tests, and therefore the potential for contiguity testing of false positive results.  相似文献   

Global trends in milk quality: implications for the Irish dairy industry     

SJ More 《Irish veterinary journal》2009,62(Z4):S5

The quality of Irish agricultural product will become increasingly important with the ongoing liberalisation of international trade. This paper presents a review of the global and Irish dairy industries; considers the impact of milk quality on farm profitability, food processing and human health, examines global trends in quality; and explores several models that are successfully being used to tackle milk quality concerns. There is a growing global demand for dairy products, fuelled in part by growing consumer wealth in developing countries. Global dairy trade represents only 6.2% of global production and demand currently outstrips supply. Although the Irish dairy industry is small by global standards, approximately 85% of annual production is exported annually. It is also the world's largest producer of powdered infant formula. Milk quality has an impact on human health, milk processing and on-farm profitability. Somatic cell count (SCC) is a key measure of milk quality, with a SCC not exceeding 400,000 cells/ml (the EU milk quality standard) generally accepted as the international export standard. There have been ongoing improvements in milk quality among both established and emerging international suppliers. A number of countries have developed successful industry-led models to tackle milk quality concerns. Based on international experiences, it is likely that problems with effective translation of knowledge to practice, rather than incomplete knowledge per se, are the more important constraints to national progress towards improved milk quality.  相似文献   

Production of volatiles in brown boronia flowers after harvest. I: Effect of clonal type and incubation temperature     

Hazel S. Mactavish  Robert C. Menary 《The Journal of Horticultural Science and Biotechnology》2013,88(4):436-439

Summary

The potential for enhanced concentrations of essential oils (solvent-extracted floral products) in flowers from four genetically distinct clones of brown boronia (Boronia megastigma Nees) as a result of post-harvest incubation was assessed. Flowers were sampled throughout 48 h of incubation at 12 and 308C. There was significant variation in the changes observed between clones. Increases in the concentration of floral extract as a result of incubation varied from 3% to 19%, the maximum concentration of floral extract observed was 2.13% (dry-weight basis). The volatile portion of the extract increased by between 25 and 117%, and the concentration of b-ionone, the main volatile of interest, increased by between 45 and 181%. The maximum concentration of total volatiles observed was 0.47%, and of b-ionone, 0.165%; all values being expressed as a percentage of dry flower weight. The most significant increase in floral extract, total volatiles and b-ionone after harvest, occurred in clone 250. Increases in all components were greater as a result of incubation at 128C for 48 h compared with 308C for 12 h.  相似文献