Morphological identification of fungi associated with Eichhornia crassipes (Mart.-Solms) Laubach in the Wouri River Basin, Douala, Cameroon
- Authors: Voukeng, Kenfack S N , Coombes, Candice A , Weyl, Philip S R , Djeugoue, F , Hill, Martin P
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/423785 , vital:72093 , xlink:href="https://doi.org/10.2989/16085914.2019.1636760"
- Description: In many parts of the world, excess growth of Eichhornia crassipes (Pontederiaceae) poses a serious threat to aquatic environments. In Cameroon, where manual clearing is still undertaken, little is known about fungal diversity associated with the plant, or its potential for biological control. Surveys of the Wouri River Basin in the Littoral Region of Cameroon were conducted during a rainy season (May–October 2014) and a dry season (November 2015–April 2016) at various sites, to identify fungi associated with water hyacinth. Fungi were isolated and identified from symptomatic plant parts collected. In the rainy season, 130 fungal isolates belonging to 12 genera were identified morphologically, whereas 299 isolates belonging to 23 genera were identified during the dry season. With the exception of Fusarium oxysporum and Phytophthora sp., the genera represented new records for Cameroon, and Chaetomium strumarium, Colletotrichum gloesporioides, C. acutatum, C. dematium, Curvularia pallescens and Pytomyces chartarum were considered new host records for E. crassipes in Africa. Isolates of Acremonium zonatum, Chaetomium strumarium, Alternaria eichhorniae, Phytophthora sp. and Rhizoctonia sp. showed the highest frequency of occurrence on E. crassipes in the Wouri River Basin and, given their record as plant pathogens, could be potentially useful in the development of mycoherbicides for this weed in Cameroon.
- Full Text:
- Date Issued: 2019
Simulated global increases in atmospheric CO2 alter the tissue composition, but not the growth of some submerged aquatic plant bicarbonate users growing in DIC rich waters
- Authors: Hussner, Andreas , Smith, Rosali , Mettler-Altmann, Tabea , Hill, Martin P , Coetzee, Julie A
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/419388 , vital:71640 , xlink:href="https://doi.org/10.1016/j.aquabot.2018.11.009"
- Description: Current global change scenarios predict an increase in atmospheric CO2 from the current 380 ppm to a value ranging from 540 ppm to 960 ppm by the year 2100. The effects of three air CO2 levels (400, 600 and 800 ppm) on five submerged aquatic plants that utilize HCO3− were studied, using the elevated CO2 Open Top Chamber facility at Rhodes University (Grahamstown, South Africa). Plants grew in water with two different initial dissolved inorganic carbon (DIC) concentrations of 1.5 and 3.0 mM. Overall, the growth rates and biomass allocation to roots were not affected by the initial DIC and air CO2, even though differences between the species were found. Furthermore, no overall effects were found on net photosynthesis, chlorophyll and starch content, even though significant effects of CO2 and DIC were observed in some species. In contrast, with increasing DIC and air CO2 a significant global decline in leaf nitrogen content linked with an increased C:N molar ratio was observed. The results indicate that submerged aquatic HCO3− users will be less affected by atmospheric CO2 increases when growing in DIC rich waters, in comparison to obligate CO2 users growing under CO2 limiting conditions as documented in previous studies. However, the changes found in plant nitrogen illustrate that atmospheric CO2 increases will affect nitrogen absorption by submerged plants, with subsequent ecosystem level effects.
- Full Text:
- Date Issued: 2019
The attitudes of riparian communities to the presence of water hyacinth in the Wouri River Basin, Douala, Cameroon
- Authors: Voukeng, Kenfack S N , Weyl, Philip S R , Hill, Martin P , Weyl, Philip , Chi, N
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/423822 , vital:72096 , xlink:href="https://doi.org/10.2989/16085914.2018.1538868"
- Description: Since publication of the first record of Eichhornia crassipes in Cameroon in 1997, the weed has become highly invasive in the Wouri River Basin. Between June and September 2014, a socio-economic survey using participatory and qualitative methods was undertaken in the riparian villages of the Wouri River Basin to assess the perception of respondents to the presence of water hyacinth. The survey revealed that water hyacinth was a significant threat to activities along the river, which included fishing, sand extraction and river transportation. The presence of water hyacinth mats reduced catch rates of several common fish species, river transportation by 75%, and significantly reduced the income for sand extraction. Cameroon employs manual clearing of water hyacinth; however, respondents indicated they would consider other control methods, provided they do not have any negative impacts.
- Full Text:
- Date Issued: 2019
The South America tomato leafminer, Tuta absoluta (Lepidoptera: Gelechiidae), spreads its wings in Eastern Africa: distribution and socioeconomic impacts
- Authors: Aigbedion-Atalor, Pascal O , Hill, Martin P , Zalucki, Myron P , Obala, Francis , Idriss, Gamal E , Midingoyi, Soul-Kifouly G , Chidege, Maneno , Ekesi, Sunday , Mohamed, Samira Abuelgasim
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/423859 , vital:72099 , xlink:href="https://doi.org/10.1093/jee/toz220"
- Description: Following the arrival of Tuta absoluta Meyrick in the eastern African subregion in 2012, several studies have shown numerous ecological aspects of its invasion. We investigated the impact of T. absoluta on people’s livelihoods across four counties of Kenya. Here, 200 farmers in the country were interviewed in person using semistructured questionnaires. In addition to livelihood surveys, T. absoluta distribution was mapped between 2016 and 2018 to determine its current distribution across four countries (Kenya, Sudan, Tanzania, and Uganda) in the subregion. Albeit a recent invader, T. absoluta is abundant and distributed throughout the subregion and is viewed as the worst invasive alien species of agriculturally sustainable livelihoods by tomato farmers. The arrival of T. absoluta in the subregion has resulted in livelihood losses and increased both the cost of tomato production and frequency of pesticide application. We recommend the implementation of biological control along, with other control measures in an integrated approach, against T. absoluta in the subregion, where its impact on sustainable livelihoods is serious and long-term control strategies are required to curb its detrimental effects.
- Full Text:
- Date Issued: 2019
The thermal physiology of Stenopelmus rufinasus and Neohydronomus affinis (Coleoptera: Curculionidae), two biological control agents for the invasive alien aquatic weeds, Azolla filiculoides and Pistia stratiotes in South Africa.
- Authors: Mvandaba, Sisanda F , Owen, Candice A , Hill, Martin P , Coetzee, Julie A
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/444467 , vital:74243 , https://doi.org/10.1080/09583157.2018.1525484
- Description: Water lettuce, Pistia stratiotes, and red water fern, Azolla filiculoides, are floating aquatic macrophytes that have become problematic in South Africa. Two weevils, Neohydronomus affinis and Stenopelmus rufinasus, are successful biological control agents of these two species in South Africa. The aim of this study was to investigate the thermal requirements of these two species to explain their establishment patterns in the field. Laboratory results showed that both weevils are widely tolerant to cold and warm temperatures.
- Full Text:
- Date Issued: 2019
Biological control of Salvinia molesta in South Africa revisited
- Authors: Martin, Grant D , Coetzee, Julie A , Weyl, Philip S R , Parkinson, Matthew C , Hill, Martin P
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/103878 , vital:32318 , https://doi.org/10.1016/j.biocontrol.2018.06.011
- Description: The aquatic weed Salvinia molesta D.S. Mitch. (Salviniaceae) was first recorded in South Africa in the early 1900s, and by the 1960s was regarded as one of South Africa’s worst aquatic weeds. Following the release of the weevil, Cyrtobagous salviniae Calder and Sands (Coleoptera: Curculionidae) in 1985, the weed is now considered under successful biological control. However, the post-release evaluation of this biological control programme has been ad hoc, therefore, to assess the efficacy of the agent, annual quantitative surveys of South African freshwater systems have been undertaken since 2008. Over the last ten years, of the 57 S. molesta sites visited annually in South Africa, the weevil has established at all of them. Eighteen sites are under successful biological control, where the weed no longer poses a threat to the system and 19 are under substantial biological control, where biological control has reduced the impact of the weed. Since 2008, the average percentage weed cover at sites has declined significantly from 51–100% cover to 0–5% cover in 2017 (R2 = 0.78; P < 0.05). Observations of site-specific characteristics suggest that biological control is most effective at small sites and more difficult at larger and shaded sites. Our findings show that S. molesta remains under good biological control in South Africa, however, some sites require intermittent strategic management, such as augmentative releases of C. salviniae.
- Full Text:
- Date Issued: 2018
Development of a Postharvest Cold Treatment for Cryptophlebia peltastica (Lepidoptera: Tortricidae) for Export of Litchis From South Africa
- Authors: Moore, Sean D , Kirkman, Wayne , Peyper, Mellissa , Thackeray, Sean R , Marsberg, Tamryn , Albertyn, Sonnica , Hill, Martin P
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/423729 , vital:72089 , xlink:href="https://doi.org/10.1093/jee/toy287"
- Description: The litchi moth, Cryptophlebia peltastica (Meyrick) (Lepidoptera: Tortricidae), is endemic to sub-Saharan Africa and certain Indian Ocean islands. It is an important pest of litchis and to a lesser extent macadamias. Litchis are exported to certain markets that consider C. peltastica as a phytosanitary pest. Consequently, an effective postharvest phytosanitary treatment is required. This study sought to develop a cold disinfestation treatment for this purpose. First, it was established that the fifth instar was the most cold-tolerant larval stage, as it was the only instar for which there was still some survival after 12 d at 1°C. It was then determined that cold treatment trials could be conducted in artificial diet, as there was no survival of fifth instar C. peltastica in litchis after only 9 d at 1°C, whereas it took 15 d at this temperature before no survival of fifth instar C. peltastica was recorded in artificial diet. Consequently, cold susceptibility of fifth instar C. peltastica and the most cold-tolerant larval stages (fourth and fifth instar) of false codling moth, Thaumatotibia leucotreta (Meyrick) (Lepidoptera: Tortricidae), were compared in artificial diet. There was no survival of C. peltastica after 13 d at 1°C, whereas this was only so for T. leucotreta after 16 d. Consequently, it can be concluded that any cold treatment that has been proven effective against T. leucotreta would be as effective against C. peltastica. Finally, it was confirmed that the cold susceptibility of T. leucotreta in artificial diet did not overestimate the effect of cold on T. leucotreta larvae in litchis.
- Full Text:
- Date Issued: 2018
Developmental and reproductive performance of a specialist herbivore depend on seasonality of, and light conditions experienced by, the host plant
- Authors: Zachariades, Uyi O O, , Heshula, Lelethu U P , Hill, Martin P
- Date: 2018
- Language: English
- Type: article , text
- Identifier: http://hdl.handle.net/10962/59845 , vital:27667 , https://doi.org/10.1371/journal.pone.0190700
- Description: Host plant phenology (as influenced by seasonality) and light-mediated changes in the phenotypic and phytochemical properties of leaves have been hypothesised to equivocally influence insect herbivore performance. Here, we examined the effects of seasonality, through host plant phenology (late growth-season = autumn vs flowering-season = winter) and light environment (shade vs full-sun habitat) on the leaf characteristics of the invasive alien plant, Chromolaena odorata. In addition, the performance of a specialist folivore, Pareuchaetes insulata, feeding on leaves obtained from both shaded and full-sun habitats during autumn and winter, was evaluated over two generations. Foliar nitrogen and magnesium contents were generally higher in shaded plants with much higher levels during winter. Leaf water content was higher in shaded and in autumn plants. Total non-structural carbohydrate (TNC) and phosphorus contents did not differ as a function of season, but were higher in shaded foliage compared to full-sun leaves. Leaf toughness was noticeably higher on plants growing in full-sun during winter. With the exception of shaded leaves in autumn that supported the best performance [fastest development, heaviest pupal mass, and highest growth rate and Host Suitability Index (HSI) score], full-sun foliage in autumn surprisingly also supported an improved performance of the moth compared to shaded or full-sun leaves in winter. Our findings suggest that shaded and autumn foliage are nutritionally more suitable for the growth and reproduction of P. insulata. However, the heavier pupal mass, increased number of eggs and higher HSI score in individuals that fed on full-sun foliage in autumn compared to their counterparts that fed on shaded or full-sun foliage in winter suggest that full-sun foliage during autumn is also a suitable food source for larvae of the moth. In sum, our study demonstrates that seasonal and light-modulated changes in leaf characteristics can affect insect folivore performance in ways that are not linear.
- Full Text:
- Date Issued: 2018
Evidence for a new regime shift between floating and submerged invasive plant dominance in South Africa
- Authors: Strange, Emily F , Hill, Martin P , Coetzee, Julie A
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/423993 , vital:72114 , xlink:href="https://doi.org/10.1007/s10750-018-3506-2"
- Description: Classical biological control for the management of floating invasive plants has been highly successful in South Africa. However, restoring ecosystem services has been compromised by a new suite of submerged invasive plants. This study proposes that biological control of floating invasive macrophytes acts as a catalyst in a regime shift between floating and submerged invasive plant dominance. Regime shifts are large and sudden changes in the structure and functioning of ecosystems. The proposed shift is driven by the rapid decomposition of floating plants and subsequent increase in availability of nutrients and light. A mesocosm experiment explored the effect of biological control on floating Pistia stratiotes L. (Araceae) upon the growth of invasive submerged Egeria densa Planch. (Hydrocharitaceae), and native submerged plant species of the same family; Lagarosiphon major (Ridl.) Moss (Hydrocharitaceae). The results revealed a cascade effect of biological control of P. stratiotes on the availability of nitrogen, resulting in increased relative growth rates and invasive capacity for E. densa. In contrast, the native L. major could not compete with healthy or damaged P. stratiotes. These findings highlight the vulnerability of South African freshwater systems to submerged plant invasions and demonstrate the importance of a more holistic approach to invasive plant management.
- Full Text:
- Date Issued: 2018
Integrating chemical control with sterile insect releases in an integrated pest management programme for Thaumatotibia leucotreta
- Authors: Nepgen, Eugene , Moore, Sean D , Hill, Martin P
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/423770 , vital:72092 , xlink:href="https://doi.org/10.1111/jen.12487"
- Description: False codling moth Thaumatotibia leucotreta (Meyrick) (Lepidoptera: Tortricidae) is an important indigenous pest of citrus in southern Africa. Successful control is dependent upon integration of area-wide sterile insect releases and other suppression methods. The aim of this work was to test pyrethroid and organophosphate-based insecticides (tau-fluvalinate and chlorpyrifos) for their residual effect on mortality of released irradiated T. leucotreta male moths. Both of these insecticides were effective in killing irradiated T. leucotreta for 7 days after application on leaves, after which degradation of the active ingredient resulted in a marked reduction in efficacy after 14 days and rendering them harmless. Mortality was found to be similar for irradiated and non-irradiated male T. leucotreta after treatment. Consequently, even though these insecticides might have an effect on moths in the field, ratios of sterile:wild moths should not be altered. Supporting field data from six sites in the Sundays River Valley over a season of sterile insect releases showed the conventional chemical crop protection programme to be as effective as an integrated pest management programme in facilitating effective control of T. leucotreta through sterile insect releases. The study also confirmed that the ratios of sterile:wild male moths in the commercial citrus orchards were not affected by the application of insecticides. These findings confirm the high potential of sterile insect releases for control of T. leucotreta in citrus.
- Full Text:
- Date Issued: 2018
Morphological, genetic and biological characterisation of a novel alphabaculovirus isolated from Cryptophlebia peltastica (Lepidoptera: Tortricidae)
- Authors: Marsberg, Tamryn , Jukes, Michael , Krejmer-Rabalska, Martyna , Rabalski, Lukasz , Knox, Caroline M , Moore, Sean D , Hill, Martin P , Szewczyk, Boguslaw
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/419330 , vital:71635 , xlink:href="https://doi.org/10.1016/j.jip.2018.08.006"
- Description: Cryptophlebia peltastica is an agricultural pest of litchis and macadamias in South Africa with phytosanitary status for certain markets. Current control methods rely on chemical, cultural and classical biological control. However, a microbial control option has not been developed. An Alphabaculovirus from C. peltastica was recovered from a laboratory reared colony and morphologically characterised by transmission electron microscopy (TEM). Analysis of occlusion bodies indicated a single NPV (SNPV) varying in size from 421 to 1263 nm. PCR amplification and sequencing of the polh gene region using universal primers followed by BLAST analysis revealed a 93% similarity to a partial polh gene sequence from Epinotia granitalis NPV. Further genetic characterisation involving single restriction endonuclease (REN) digestion of genomic DNA was carried out to generate profiles for comparison against other baculovirus species and potential new isolates of the same virus. The complete genome of the virus was sequenced, assembled and analysed for a more comprehensive genetic analysis. The genome was 115 728 base pairs (bp) in length with a GC content of 37.2%. A total of 126 open reading frames (ORFs) were identified with minimal overlap and no preference in orientation. Bioassays were used to determine the virulence of the NPV against C. peltastica. The NPV was virulent against C. peltastica with an LC50 value of 6.46 × 103 OBs/ml and an LC90 value of 2.46 × 105 OBs/ml, and time mortality ranging between 76.32 h and 93.49 h. This is the first study to describe the isolation and genetic characterisation of a novel SNPV from C. peltastica, which has potential for development into a biopesticide for the control of this pest in South Africa.
- Full Text:
- Date Issued: 2018
Synergies between research organisations and the wider community in enhancing weed biological control in South Africa
- Authors: Martin, Grant D , Hill, Martin P , Coetzee, Julie A , Weaver, Kim N , Hill, Jaclyn M
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/68452 , vital:29258 , https://doi.org/10.1007/s10526-017-9846-4
- Description: Biological control offers a cost effective and ecologically sustainable tool for the management of invasive alien plants. Its implementation, however, has historically been slow and poorly co-ordinated. In South Africa, as in many other countries, most aspects of biological control programmes were done by researchers, but from 1995 onwards, with the advent of the Working for Water Programme, a more inclusive approach to biological control has been adopted. In this paper, we report on the development of community-based biological control implementation programmes in South Africa, after 1995, and highlight a number of initiatives, including employing persons with disabilities at mass-rearing facilities and in particular, we outline a suite of educational and outreach programmes for the general public and for schools, which have increased capacity, education and employment in the field of weed biological control.
- Full Text:
- Date Issued: 2018
The contributions of biological control to reduced plant size and biomass of water hyacinth populations
- Authors: Jones, Roy W , Hill, Jaclyn M , Coetzee, Julie A , Hill, Martin P
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/68803 , vital:29326 , https://0-doi.org.wam.seals.ac.za/10.1007/s10750-017-3413-y
- Description: Water hyacinth is invasive in many countries, where it reduces aquatic biodiversity and limits water resource utilisation. Biological control of water hyacinth has been successful in South Africa, but has suffered from a lack of empirical data to prove causation. Insect exclusion trials were conducted to quantify the contribution of Neochetina eichhorniae and N. bruchi to the integrated control of water hyacinth on the Nseleni River, South Africa. Insecticide was not expected to induce phytotoxicity, but would prevent weevil damage in water hyacinth plants; and weevil herbivory was predicted to reduce plant petiole length, and above/below surface biomass. Results showed that insecticide had no phytotoxic effects and excluded weevils for 3 weeks, providing a baseline for field applications. Biological control on the Nseleni River directly affected water hyacinth biomass and petiole length, but did not affect plant cover. Plants subject to weevil herbivory demonstrated reductions in above and below surface biomass and had shorter petioles compared to insect-free plants. Dead biomass was also higher in biological control treatments. Biological control strongly affects plant size, biomass and vigour; however, further integrated control is required to facilitate reduction in mat cover, which is the goalpost for successful control of floating aquatic plants.
- Full Text: false
- Date Issued: 2018
Assessing the status of biological control as a management tool for suppression of invasive alien plants in South Africa
- Authors: Zachariades, Costas , Paterson, Iain D , Strathie, Lorraine W , Hill, Martin P , van Wilgen, Brian W
- Date: 2017
- Language: English
- Type: article , text
- Identifier: http://hdl.handle.net/10962/59762 , vital:27646 , https://doi.org/10.4102/abc.v47i2.2142
- Description: Biological control of invasive alien plant (IAP) species is the use of introduced, highly selective natural enemies (usually herbivorous arthropods or pathogens) to control plants. It has been used in 130 countries as a valuable tool for the control of IAP species, with a total of over 550 biological control agents having been released (Winston et al. 2014). The benefits of biological control to natural ecosystems are significant (Van Driesch et al. 2010), with some specific examples of threatened indigenous species being protected by the action of biological control agents (Barton et al. 2007; Meyer, Fourdrigniez & Taputuarai 2011). Detailed analyses of programmes on biological control of IAPs have also clearly indicated that the risks of non-target effects from biological control agents are minimal (Fowler, Syrett & Hill 2000; Funasaki et al. 1988; Moran & Hoffmann 2015; Paynter et al. 2004; Pemberton 2000; Suckling & Sforza 2014). Less than 1% of all the agents released have a negative impact on non-target plant populations, and those that do could have been predicted to do so, and would not be released today (Suckling & Sforza 2014).
- Full Text:
- Date Issued: 2017
Biology and rearing of Ectomyeolis ceratoniae Zeller (Lepidoptera: Pyralidae) carob moth, a pest of multiple crops in South Africa
- Authors: Thackeray, Sean R , Moore, Sean D , Strathie, Lorraine W , Kirkman, Wayne , Hill, Martin P
- Date: 2017
- Language: English
- Type: article , text
- Identifier: http://hdl.handle.net/10962/59799 , vital:27652 , https://doi.org/10.4001/003.025.0474
- Description: Ectomyeolis ceratoniae Zeller (Lepidoptera: Pyralidae), carob moth, is a pest of several crops in South Africa. A laboratory culture was established from field-collected larvae infesting mummified pecan nuts. Biological parameters of larvae reared on an artificial diet were measured. The insect goes through five larval instars, and the head capsule sizes of the five instars were determined to be <0.34 mm, 0.35-0.64 mm, 0.65-0.94 mm, 0.95-1.14 mm and >0.15 mm for the five instars, respectively. The insect was reared individually and communally in glass vials, the latter to develop a mass-rearing technique. Developmental time from neonate to pupa was significantly slower when larvae were individually reared (38.18 ±1.2 days) compared to when they were communally reared (24.6 ± 0.65 days). A microsporidian infection (Nosema sp.) was recorded in the culture, causing significantly (fy6 = 14.99, P = 0.0082) higher mortality of communally reared larvae (76.25 % ± 11.87) than individually reared larvae (24.9 % ± 9.6).
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- Date Issued: 2017
Changes in chemical composition of essential oils from leaves of different Lantana camara L. (Verbenaceae) varieties after feeding by the introduced biological control agent, Falconia intermedia Distant (Hemiptera: Miridae)
- Authors: Ngxande-Koza, Samella W , Heshula, Lelethu U P , Hill, Martin P
- Date: 2017
- Language: English
- Type: article , text
- Identifier: http://hdl.handle.net/10962/59834 , vital:27664 , https://doi.org/10.4001/003.025.0462
- Description: Lantana camara L. (Verbenaceae) is one of the most problematic plant invaders in South Africa and has been targeted for biological control for over 50 years. Essential oil constituents which often change in response to insect herbivory are reported to play a crucial role in plant-insect interactions. However, nothing is known about the chemical profiles of essential oils of L. camara varieties in South Africa and how this changes under herbivory. Therefore, essential oils were collected using hydrodistillation from undamaged and insect-damaged leaves of four L. camara varieties and analysed using gas chromatography-mass spectrometry to elucidate their chemical profiles. A total of 163 compounds were identified from the undamaged leaves of the various L. camara varieties. Feeding by the biocontrol agent Falconia intermedia Distant (Hemiptera: Miridae) resulted in changes in the quality and quantity of chemical constituents of the essential oils. Only 75 compounds were identified from the insect-damaged leaves of L. camara varieties. Terpenes were the major components across the varieties, while caryophyllene, hexane, naphthalene, copaene and a-caryophyllene were common in all the varieties tested from both undamaged and insect-damaged leaves. Results from this study indicated the chemical distinctiveness of the Whitney Farm variety from other varieties. The changes in chemical concentrations indicated that feeding by the mirid on L. camara varieties causes an induction by either reducing or increasing the chemical concentrations. These inductions following the feeding by F. intermedia could be having a negative impact on the success of biological control against L. camara varieties. However, the focus of this paper is to report on the chemical baseline of L. camara varieties. Hence, comparisons of chemical compound concentrations of L. camara essential oils tested and the feeding-induced changes with respect to their quality and quantity are discussed.
- Full Text:
- Date Issued: 2017
Community entomology: insects, science and society
- Authors: Weaver, Kim N , Hill, Jaclyn M , Martin, Grant D , Paterson, Iain D , Coetzee, Julie A , Hill, Martin P
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/123343 , vital:35429 , https://hdl.handle.net/10520/EJC-c859bebd5
- Description: Educative outreach programmes have been found to be effective ways in which to raise awareness around basic scientific concepts. The Biological Control Research Group (BCRG) in the Department of Zoology and Entomology at Rhodes University, South Africa, is involved in community engaged initiatives that aim to be interactive and informative around entomology, and more specifically, the use of biological control against invasive alien plants. As a higher education institution, Rhodes University has a civic responsibility to engage with local communities and work with them around local challenges. Three groups of activities undertaken by the BCRG in partnership with local schools and other community partners are described and assessed in this paper as a way of assessing them and exploring future research areas around the aims and outcomes of these programmes.
- Full Text:
- Date Issued: 2017
Isolation, identification and genetic characterisation of a microsporidium isolated from carob moth, Ectomyelois ceratoniae (Zeller) (Lepidoptera: Pyralidae)
- Authors: Lloyd, Melissa , Knox, Caroline M , Hill, Martin P , Moore, Sean D , Thackeray, Sean R
- Date: 2017
- Language: English
- Type: article , text
- Identifier: http://hdl.handle.net/10962/59874 , vital:27674 , https://doi.org/10.4001/003.025.0529
- Description: 'Microsporidia' is a term used for organisms belonging to the phylum Microspora, which contains approximately 187 genera and 1500 species (Corradi 2015). They are obligate intracellular parasites with no active metabolic stages of the life cycle occurring outside of the host cells (Franzen & Muller 1999; Garcia 2002; Tsai et al. 2003; Huang et al. 2004). They exhibit eukaryotic characteristics such as a membrane-bound nucleus, an intracytoplasmic membrane system, and chromosome separation occurs on mitotic spindles. However, they also exhibit prokaryotic characteristics such as possession of a 70S ribosome, lack of true mitochondria and peroxisomes, a simple version of the Golgi apparatus, and a small genome which is much less complex than those of most eukaryotes (Franzen & Muller 1999; Garcia 2002). Microspo- ridia are parasitic in all major groups of animals, both vertebrates and invertebrates (Sprague 1977; Franzen & Muller 1999). Microsporidia were first recognised as pathogens in silkworms by Nageli (1857), and now have been found to infect many hosts such as humans, insects, fish and mammals (Stentiford et al. 2016).
- Full Text:
- Date Issued: 2017
More is not necessarily better: the interaction between insect population density and culture age of fungus on the control of invasive weed water hyacinth
- Authors: Ray, Puja , Hill, Martin P
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/424777 , vital:72183 , xlink:href="https://doi.org/10.1007/s10750-015-2454-3"
- Description: The possibilities of a positive or negative impact the biocontrol agents may have on each other as well as on the control of the weed itself, inspired us to study the interactions between the mirid, Eccritotarsus catarinensis and the phytopathogen, Acremonium zonatum, biocontrol agents of water hyacinth, Eichhornia crassipes. Observations were made on disease initiation time of A. zonatum grown for different time durations with different insect densities on water hyacinth. In absence of mirids, the lowest (3.1 days) and the highest (5.1 days) disease initiation time was observed using 21 and 42 days old culture respectively. In treatments involving mirids, the shortest (1.78 days) and the longest (13.22 days) disease initiation time by A. zonatum was observed on water hyacinth with 10 and 20 mirids/plant respectively. By the 30th day, maximum percentage damage (77.9%) was observed in the treatment of 21 day old fungal culture with 20 mirid density/plant despite of initial delay in disease initiation. This result suggests an initial development of a plant defense response due to mirid feeding delaying the pathogen from establishing. Extensive studies involving multitrophic interactions should be an essential part of pre-release assessments to enhance the success rates of biological control of weeds.
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- Date Issued: 2017
Potential of entomopathogenic fungal isolates for Control of the soil-dwelling life stages of Thaumatotibia leucotreta Meyrick (Lepidoptera: Tortricidae) in citrus
- Authors: Coombes, Candice A , Hill, Martin P , Dames, Joanna F , Moore, Sean D
- Date: 2017
- Language: English
- Type: article , text
- Identifier: http://hdl.handle.net/10962/59885 , vital:27684 , https://doi.org/10.4001/003.025.0235
- Description: Thaumatotibia leucotreta Meyrick (Lepidoptera: Tortricidae) is a key pest of citrus in South Africa. In addition to the fruit damage caused, export markets such as the United States, South Korea and China regulate T. leucotreta as a phytosanitary organism in addition to restricting the use of pesticides on exported fruit (Grout & Moore 2015; SA-DAFF 2015). The bulk of citrus in South Africa is exported (Citrus Growers' Association 2015). Thus, the control of T. leucotreta is crucial. Consequently, the citrus industry adopts a zero tolerance approach controlling the pest, being strongly reliant on integrated pest management (Moore & Hattingh 2012). Numerous control options are available, but are largely limited to use against the above-ground life stages of this pest: eggs, neonates and adults (Moore & Hattingh 2012; Grout & Moore 2015).
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- Date Issued: 2017