Development of a Postharvest Cold Treatment for Cryptophlebia peltastica (Lepidoptera: Tortricidae) for Export of Litchis From South Africa
- Moore, Sean D, Kirkman, Wayne, Peyper, Mellissa, Thackeray, Sean R, Marsberg, Tamryn, Albertyn, Sonnica, Hill, Martin P
- 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
- 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
Evidence for a new regime shift between floating and submerged invasive plant dominance in South Africa
- Strange, Emily F, Hill, Martin P, Coetzee, Julie A
- 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
- 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
- Nepgen, Eugene, Moore, Sean D, Hill, Martin P
- 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
- 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)
- Marsberg, Tamryn, Jukes, Michael, Krejmer-Rabalska, Martyna, Rabalski, Lukasz, Knox, Caroline M, Moore, Sean D, Hill, Martin P, Szewczyk, Boguslaw
- 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
- 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
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.
- Full Text:
- Date Issued: 2017
- 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.
- Full Text:
- Date Issued: 2017
Entomopathogenic fungi as control agents of Thaumatotibia leucotreta in citrus orchards: field efficacy and persistence
- Coombes, Candice A, Hill, Martin P, Moore, Sean D, Dames, Joanna F
- Authors: Coombes, Candice A , Hill, Martin P , Moore, Sean D , Dames, Joanna F
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/417956 , vital:71497 , xlink:href="https://doi.org/10.1007/s10526-016-9756-x"
- Description: Entomopathogenic fungal isolates Beauveria bassiana (Balsamo) Vuillemin (Hypocreales: Cordycipitaceae) strain G Ar 17 B3 and Metarhizium anisopliae (Metchnikoff) Sorokin (Hypocreales: Clavicipitaceae) strain FCM Ar 23 B3 have been identified as effective control agents of the important citrus pest Thaumatotibia leucotreta (Meyrick) (Lepidoptera: Tortricidae) wandering fifth instars under laboratory conditions. This study is the first report on the ability of these isolates to persist and reduce T. leucotreta infestation in commercial citrus orchards in South Africa. A reduction in pest infestation of between 28 and 82 % upon trial completion was reported. Both isolates were recovered from soil samples collected five months post-application with high host density and moderate to high soil moisture favouring recovery. Low soil moisture negatively influenced the persistence of both isolates and the control efficiency of B. bassiana. These results provide evidence and support for the future use of these isolates against T. leucotreta thus warranting further investigation.
- Full Text:
- Date Issued: 2016
- Authors: Coombes, Candice A , Hill, Martin P , Moore, Sean D , Dames, Joanna F
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/417956 , vital:71497 , xlink:href="https://doi.org/10.1007/s10526-016-9756-x"
- Description: Entomopathogenic fungal isolates Beauveria bassiana (Balsamo) Vuillemin (Hypocreales: Cordycipitaceae) strain G Ar 17 B3 and Metarhizium anisopliae (Metchnikoff) Sorokin (Hypocreales: Clavicipitaceae) strain FCM Ar 23 B3 have been identified as effective control agents of the important citrus pest Thaumatotibia leucotreta (Meyrick) (Lepidoptera: Tortricidae) wandering fifth instars under laboratory conditions. This study is the first report on the ability of these isolates to persist and reduce T. leucotreta infestation in commercial citrus orchards in South Africa. A reduction in pest infestation of between 28 and 82 % upon trial completion was reported. Both isolates were recovered from soil samples collected five months post-application with high host density and moderate to high soil moisture favouring recovery. Low soil moisture negatively influenced the persistence of both isolates and the control efficiency of B. bassiana. These results provide evidence and support for the future use of these isolates against T. leucotreta thus warranting further investigation.
- Full Text:
- Date Issued: 2016
Heterogeneity in virulence relationships between Cryptophlebia leucotreta granulovirus isolates and geographically distinct host populations: Lessons from codling moth resistance to CpGV-M
- Opoku-Debrah, John K, Hill, Martin P, Knox, Caroline M, Moore, Sean D
- Authors: Opoku-Debrah, John K , Hill, Martin P , Knox, Caroline M , Moore, Sean D
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/417998 , vital:71500 , xlink:href="https://doi.org/10.1007/s10526-016-9728-1"
- Description: In South Africa, the baculovirus Cryptophlebia leucotreta granulovirus (CrleGV) is used to control the citrus pest Thaumatotibia leucotreta (Meyrick) (Lepidoptera: Tortricidae). However, the risk associated with continuous application of a single active ingredient is resistance. In order to manage resistance should it occur in field populations of T. leucotreta in South Africa, five new CrleGV genotypes from geographically distinct insect populations which were shown to exhibit some degree of phenotypic variation were recovered and genetically characterized. In droplet bioassays using seven CrleGV isolates against five T. leucotreta populations, some isolates were found to show higher virulence to some host populations than others. There were marked differences in the LD50 values of isolates and the number of occlusion bodies required per larva ranged between 0.79 and 3.12. The significance of these findings with respect to the application of CrleGV biopesticides and the management of resistance is discussed.
- Full Text:
- Date Issued: 2016
- Authors: Opoku-Debrah, John K , Hill, Martin P , Knox, Caroline M , Moore, Sean D
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/417998 , vital:71500 , xlink:href="https://doi.org/10.1007/s10526-016-9728-1"
- Description: In South Africa, the baculovirus Cryptophlebia leucotreta granulovirus (CrleGV) is used to control the citrus pest Thaumatotibia leucotreta (Meyrick) (Lepidoptera: Tortricidae). However, the risk associated with continuous application of a single active ingredient is resistance. In order to manage resistance should it occur in field populations of T. leucotreta in South Africa, five new CrleGV genotypes from geographically distinct insect populations which were shown to exhibit some degree of phenotypic variation were recovered and genetically characterized. In droplet bioassays using seven CrleGV isolates against five T. leucotreta populations, some isolates were found to show higher virulence to some host populations than others. There were marked differences in the LD50 values of isolates and the number of occlusion bodies required per larva ranged between 0.79 and 3.12. The significance of these findings with respect to the application of CrleGV biopesticides and the management of resistance is discussed.
- Full Text:
- Date Issued: 2016
Nitrogen fertilisation improves growth of Chromolaena odorata (Asteraceae) and the performance of the biological control agent, Pareuchaetes insulata (Erebidae)
- Uyi, Osariyekemwen O, Zacharariades, Costas, Hill, Martin P
- Authors: Uyi, Osariyekemwen O , Zacharariades, Costas , Hill, Martin P
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/416880 , vital:71393 , xlink:href="https://doi.org/10.1080/09583157.2015.1118615"
- Description: Recent studies have demonstrated, through their contrasting results, that relationships between nitrogen levels in host plants and phytophagous insect performance are not simple. This study examined the effect of varying fertilisation regimes on the invasive alien plant, Chromolaena odorata (L.) (Asteraceae) and the response of a specialist folivore (a biological control agent), Pareuchaetes insulata (Walker) (Lepidoptera: Erebidae). C. odorata plants were treated with 3 different levels of fertilisation and plant characteristics were measured within 2–3 months of fertiliser application. Leaves from each of the three treatments were fed to newly hatched larvae until pupation in order to determine the effect of nitrogen fertilisation on herbivore performance metrics such as survival, development time, fecundity and longevity. High and medium fertilisation significantly increased foliar nitrogen concentrations, basal stem diameter, leaf length, shoot height and above-ground biomass of C. odorata plants relative to low fertilisation. When individuals of P. insulata were fed on leaves from medium- or high-fertilisation treatments, they developed faster, grew to a larger size (by 8%) and achieved higher fecundity (19–22%) than leaves from the low-fertilisation treatment. The results suggest that in mass-rearing, increased production of this biological control agent will occur in high- or medium-fertilised plants.
- Full Text:
- Date Issued: 2016
- Authors: Uyi, Osariyekemwen O , Zacharariades, Costas , Hill, Martin P
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/416880 , vital:71393 , xlink:href="https://doi.org/10.1080/09583157.2015.1118615"
- Description: Recent studies have demonstrated, through their contrasting results, that relationships between nitrogen levels in host plants and phytophagous insect performance are not simple. This study examined the effect of varying fertilisation regimes on the invasive alien plant, Chromolaena odorata (L.) (Asteraceae) and the response of a specialist folivore (a biological control agent), Pareuchaetes insulata (Walker) (Lepidoptera: Erebidae). C. odorata plants were treated with 3 different levels of fertilisation and plant characteristics were measured within 2–3 months of fertiliser application. Leaves from each of the three treatments were fed to newly hatched larvae until pupation in order to determine the effect of nitrogen fertilisation on herbivore performance metrics such as survival, development time, fecundity and longevity. High and medium fertilisation significantly increased foliar nitrogen concentrations, basal stem diameter, leaf length, shoot height and above-ground biomass of C. odorata plants relative to low fertilisation. When individuals of P. insulata were fed on leaves from medium- or high-fertilisation treatments, they developed faster, grew to a larger size (by 8%) and achieved higher fecundity (19–22%) than leaves from the low-fertilisation treatment. The results suggest that in mass-rearing, increased production of this biological control agent will occur in high- or medium-fertilised plants.
- Full Text:
- Date Issued: 2016
Screening of entomopathogenic fungi against citrus mealybug, Plannococcus citri (Hemiptera: Pseudococcidae)
- Chartier FitzGerald, Veronique C, Hill, Martin P, Moore, Sean D, Dames, Joanna F
- Authors: Chartier FitzGerald, Veronique C , Hill, Martin P , Moore, Sean D , Dames, Joanna F
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/407059 , vital:70333 , xlink:href="https://hdl.handle.net/10520/EJC195093"
- Description: Planococcus citri (citrus mealybug) is a common and damaging citrus crop pest which has proven difficult to control using conventional methods, such as chemical pesticides and insect growth regulators, particularly late in the citrus growing season. The virulence of two entomopathogenic fungal species was studied in laboratory bioassays against the crawlers and adults of P. citri. Isolates of Metarhizium anisopliae and Beauveria bassiana, collected from citrus orchards in the Eastern Cape Province in South Africa, were verified using and molecular techniques. Mealybug bioassays were performed in 24-well plates. Beauveria bassiana (GAR 17 B3) and M. anisopliae (FCM AR 23 B3) isolates both resulted in 67.5 % mortality of mealybug crawlers and B. bassiana (GB AR 23 13 3) resulted in 64 % crawler mortality with concentrations of 1 x 107 conidia/ml. These three isolates were further tested in multipledose bioassays to determine the median lethal concentration (LC50), which were 5.29 x 105conidia/ml for the M. anisopliae isolate (FCM AR 23 B3), 4.25 x 106 conidia/ml for B. bassiana (GAR 17 B3), and 6.65 x 107 conidia/ml B. bassiana (GB AR 23 13 3) for crawlers, respectively. The results of this study suggested that two isolates (M. anisopliae FCM AR 23 B3 and B. bassiana GAR 17 B3) showed potential for further development as biological control agents against citrus mealybug. Further research would be required to determine their ability to perform under field conditions.
- Full Text:
- Date Issued: 2016
- Authors: Chartier FitzGerald, Veronique C , Hill, Martin P , Moore, Sean D , Dames, Joanna F
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/407059 , vital:70333 , xlink:href="https://hdl.handle.net/10520/EJC195093"
- Description: Planococcus citri (citrus mealybug) is a common and damaging citrus crop pest which has proven difficult to control using conventional methods, such as chemical pesticides and insect growth regulators, particularly late in the citrus growing season. The virulence of two entomopathogenic fungal species was studied in laboratory bioassays against the crawlers and adults of P. citri. Isolates of Metarhizium anisopliae and Beauveria bassiana, collected from citrus orchards in the Eastern Cape Province in South Africa, were verified using and molecular techniques. Mealybug bioassays were performed in 24-well plates. Beauveria bassiana (GAR 17 B3) and M. anisopliae (FCM AR 23 B3) isolates both resulted in 67.5 % mortality of mealybug crawlers and B. bassiana (GB AR 23 13 3) resulted in 64 % crawler mortality with concentrations of 1 x 107 conidia/ml. These three isolates were further tested in multipledose bioassays to determine the median lethal concentration (LC50), which were 5.29 x 105conidia/ml for the M. anisopliae isolate (FCM AR 23 B3), 4.25 x 106 conidia/ml for B. bassiana (GAR 17 B3), and 6.65 x 107 conidia/ml B. bassiana (GB AR 23 13 3) for crawlers, respectively. The results of this study suggested that two isolates (M. anisopliae FCM AR 23 B3 and B. bassiana GAR 17 B3) showed potential for further development as biological control agents against citrus mealybug. Further research would be required to determine their ability to perform under field conditions.
- Full Text:
- Date Issued: 2016
Temperature-dependent performance and potential distribution of Pareuchaetes insulata, a biological control agent of Chromolaena odorata in South Africa
- Uyi, Osariyekemwen O, Zachariades, Costas, Hill, Martin P, McConnachie, Andrew J
- Authors: Uyi, Osariyekemwen O , Zachariades, Costas , Hill, Martin P , McConnachie, Andrew J
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/418067 , vital:71505 , xlink:href="https://doi.org/10.1007/s10526-016-9760-1"
- Description: Despite the release of about 1.9 million individuals of Pareuchaetes insulata (Walker) (Lepidoptera: Erebidae) in KwaZulu-Natal for the biological control of Chromolaena odorata (L.) King and Robinson (Asteraceae) in South Africa, the moth probably only established at one of the 30 release sites and its population level is generally low in the field. To determine whether climate incompatibility in South Africa is responsible for the poor performance of P. insulata, the effects of temperature on life-history traits were investigated under several constant temperatures. Although a degree-day model estimated between 3.9 and 10.0 generations of the moth per year in the weed’s invaded range, survival and fecundity declined while development time was prolonged at constant temperatures below 25 °C, indicating that both direct and indirect negative impacts of low winter temperatures, such as increased mortality, slow development and reduced fecundity as well as exposure to natural enemies, may partly explain the poor performance of P. insulata in South Africa.
- Full Text:
- Date Issued: 2016
- Authors: Uyi, Osariyekemwen O , Zachariades, Costas , Hill, Martin P , McConnachie, Andrew J
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/418067 , vital:71505 , xlink:href="https://doi.org/10.1007/s10526-016-9760-1"
- Description: Despite the release of about 1.9 million individuals of Pareuchaetes insulata (Walker) (Lepidoptera: Erebidae) in KwaZulu-Natal for the biological control of Chromolaena odorata (L.) King and Robinson (Asteraceae) in South Africa, the moth probably only established at one of the 30 release sites and its population level is generally low in the field. To determine whether climate incompatibility in South Africa is responsible for the poor performance of P. insulata, the effects of temperature on life-history traits were investigated under several constant temperatures. Although a degree-day model estimated between 3.9 and 10.0 generations of the moth per year in the weed’s invaded range, survival and fecundity declined while development time was prolonged at constant temperatures below 25 °C, indicating that both direct and indirect negative impacts of low winter temperatures, such as increased mortality, slow development and reduced fecundity as well as exposure to natural enemies, may partly explain the poor performance of P. insulata in South Africa.
- Full Text:
- Date Issued: 2016
The role of entomopathogenic fungi in the control of citrus pests in South Africa: cause for optimism
- Coombes, Candice A, Chartier-Fizgerald, Veronique C, Wiblin, Danielle, Dames, Joanna F, Hill, Martin P, Moore, Sean D
- Authors: Coombes, Candice A , Chartier-Fizgerald, Veronique C , Wiblin, Danielle , Dames, Joanna F , Hill, Martin P , Moore, Sean D
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , book chapter
- Identifier: http://hdl.handle.net/10962/453480 , vital:75257 , ISBN 978-1-83768-091-7 , https://iobc-wprs.org/product/the-role-of-entomopathogenic-fungi-in-the-control-of-citrus-pests-in-south-africa-cause-for-optimism/
- Description: Citrus is a highly productive crop in South Africa, but it is damaged by a number of pests that result in yield loss and have the potential to limit market access. Maximum residue limits (MRLs) imposed by importing countries have driven the need for alternative control technologies, including the use of entomopathogenic fungi (EPF). Bioprospecting in citrus orchards and seven years of bioassay trials identified Beauveria bassiana G Ar 17 B3 and Metarhizium anisopliae G 11 3 L6 and FCM Ar 23 B3 as the most virulent fungal isolates. Preliminary trials with these three fungi against the arboreal pests, California red scale, Aonidiella aurantii (Maskell), citrus mealybug, Planococcus citri (Risso) and citrus thrips, Scirtothrips aurantii Faure, have been promising. False codling moth (FCM), Thaumatotibia leucotreta (Meyrick) is the most important citrus pest in South Africa and while considerable research has been conducted on controlling the insect on the tree, the soil borne stages of this insect have largely been ignored. After laboratory bioassays, the three fungal isolates were taken to field trials. All three isolates persisted for at least six months after application to the soil. A large scale field trial, showed that although all three isolates reduced FCM infestation, isolate B. bassiana G Ar 17 B3 performed best, recording a consistent 80% reduction in FCM infestation throughout the trial period. The results of nearly 10 years of research on the potential of EPFs in the control of citrus pests in South Africa are certainly cause for optimism.
- Full Text:
- Date Issued: 2016
- Authors: Coombes, Candice A , Chartier-Fizgerald, Veronique C , Wiblin, Danielle , Dames, Joanna F , Hill, Martin P , Moore, Sean D
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , book chapter
- Identifier: http://hdl.handle.net/10962/453480 , vital:75257 , ISBN 978-1-83768-091-7 , https://iobc-wprs.org/product/the-role-of-entomopathogenic-fungi-in-the-control-of-citrus-pests-in-south-africa-cause-for-optimism/
- Description: Citrus is a highly productive crop in South Africa, but it is damaged by a number of pests that result in yield loss and have the potential to limit market access. Maximum residue limits (MRLs) imposed by importing countries have driven the need for alternative control technologies, including the use of entomopathogenic fungi (EPF). Bioprospecting in citrus orchards and seven years of bioassay trials identified Beauveria bassiana G Ar 17 B3 and Metarhizium anisopliae G 11 3 L6 and FCM Ar 23 B3 as the most virulent fungal isolates. Preliminary trials with these three fungi against the arboreal pests, California red scale, Aonidiella aurantii (Maskell), citrus mealybug, Planococcus citri (Risso) and citrus thrips, Scirtothrips aurantii Faure, have been promising. False codling moth (FCM), Thaumatotibia leucotreta (Meyrick) is the most important citrus pest in South Africa and while considerable research has been conducted on controlling the insect on the tree, the soil borne stages of this insect have largely been ignored. After laboratory bioassays, the three fungal isolates were taken to field trials. All three isolates persisted for at least six months after application to the soil. A large scale field trial, showed that although all three isolates reduced FCM infestation, isolate B. bassiana G Ar 17 B3 performed best, recording a consistent 80% reduction in FCM infestation throughout the trial period. The results of nearly 10 years of research on the potential of EPFs in the control of citrus pests in South Africa are certainly cause for optimism.
- Full Text:
- Date Issued: 2016
Two in one: cryptic species discovered in biological control agent populations using molecular data and crossbreeding experiments
- Paterson, Iain D, Mangan, Rose, Downie, Douglas A, Coetzee, Julie A, Hill, Martin P, Burke, Ashley M, Downey, Paul O, Henry, Thomas J, Compton, Stephen G
- Authors: Paterson, Iain D , Mangan, Rose , Downie, Douglas A , Coetzee, Julie A , Hill, Martin P , Burke, Ashley M , Downey, Paul O , Henry, Thomas J , Compton, Stephen G
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/424877 , vital:72191 , xlink:href="https://doi.org/10.1002/ece3.2297"
- Description: There are many examples of cryptic species that have been identified through DNA-barcoding or other genetic techniques. There are, however, very few confirmations of cryptic species being reproductively isolated. This study presents one of the few cases of cryptic species that has been confirmed to be reproductively isolated and therefore true species according to the biological species concept. The cryptic species are of special interest because they were discovered within biological control agent populations. Two geographically isolated populations of Eccritotarsus catarinensis (Carvalho) [Hemiptera: Miridae], a biological control agent for the invasive aquatic macrophyte, water hyacinth, Eichhornia crassipes (Mart.) Solms [Pontederiaceae], in South Africa, were sampled from the native range of the species in South America. Morphological characteristics indicated that both populations were the same species according to the current taxonomy, but subsequent DNA analysis and breeding experiments revealed that the two populations are reproductively isolated. Crossbreeding experiments resulted in very few hybrid offspring when individuals were forced to interbreed with individuals of the other population, and no hybrid offspring were recorded when a choice of mate from either population was offered. The data indicate that the two populations are cryptic species that are reproductively incompatible. Subtle but reliable diagnostic characteristics were then identified to distinguish between the two species which would have been considered intraspecific variation without the data from the genetics and interbreeding experiments. These findings suggest that all consignments of biological control agents from allopatric populations should be screened for cryptic species using genetic techniques and that the importation of multiple consignments of the same species for biological control should be conducted with caution.
- Full Text:
- Date Issued: 2016
- Authors: Paterson, Iain D , Mangan, Rose , Downie, Douglas A , Coetzee, Julie A , Hill, Martin P , Burke, Ashley M , Downey, Paul O , Henry, Thomas J , Compton, Stephen G
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/424877 , vital:72191 , xlink:href="https://doi.org/10.1002/ece3.2297"
- Description: There are many examples of cryptic species that have been identified through DNA-barcoding or other genetic techniques. There are, however, very few confirmations of cryptic species being reproductively isolated. This study presents one of the few cases of cryptic species that has been confirmed to be reproductively isolated and therefore true species according to the biological species concept. The cryptic species are of special interest because they were discovered within biological control agent populations. Two geographically isolated populations of Eccritotarsus catarinensis (Carvalho) [Hemiptera: Miridae], a biological control agent for the invasive aquatic macrophyte, water hyacinth, Eichhornia crassipes (Mart.) Solms [Pontederiaceae], in South Africa, were sampled from the native range of the species in South America. Morphological characteristics indicated that both populations were the same species according to the current taxonomy, but subsequent DNA analysis and breeding experiments revealed that the two populations are reproductively isolated. Crossbreeding experiments resulted in very few hybrid offspring when individuals were forced to interbreed with individuals of the other population, and no hybrid offspring were recorded when a choice of mate from either population was offered. The data indicate that the two populations are cryptic species that are reproductively incompatible. Subtle but reliable diagnostic characteristics were then identified to distinguish between the two species which would have been considered intraspecific variation without the data from the genetics and interbreeding experiments. These findings suggest that all consignments of biological control agents from allopatric populations should be screened for cryptic species using genetic techniques and that the importation of multiple consignments of the same species for biological control should be conducted with caution.
- Full Text:
- Date Issued: 2016
Agathis bishopi (Hymenoptera: Braconidae) as a potential tool for detecting oranges infested with Thaumatotibia leucotreta (Lepidoptera: Tortricidae)
- Zimba, Kennedy J, Hill, Martin P, Moore, Sean D, Heshula, Unathi
- Authors: Zimba, Kennedy J , Hill, Martin P , Moore, Sean D , Heshula, Unathi
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/423955 , vital:72108 , xlink:href="https://doi.org/10.1007/s10905-015-9526-0"
- Description: In South Africa, Thaumatotibia leucotreta is a key pest of citrus impacting its production and trade. Detection of newly infested fruit by visual inspection is challenging and poses a risk of packing infested with healthy fruit for export. Agathis bishopi is a larval endoparasitoid of T. leucotreta, attacking early larval instars. Understanding how A. bishopi parasitoids locate fruit infested with their host is of interest for developing an efficient detector for T. leucotreta infested fruit. The response of female adult A. bishopi parasitoids to olfactory and visual cues associated with T. leucotreta infested fruit were evaluated using a Y-tube olfactometer and flight tunnel. Agathis bishopi parasitoids were strongly attracted to infested fruit over healthy fruit, either when only olfactory or combinations of visual and olfactory cues were offered. Among the four synthetic compounds tested, D-limonene and ocimene elicited a strong attraction to parasitoids with response rates of 92 % and 72 % respectively. A blend of four synthetic compounds simulating T. leucotreta infested fruit odour equally elicited strong attraction to parasitoids (84 % response rate). Attraction of parasitoids to infested fruit cues was heightened by prior experience, suggesting the occurrence of associative learning. Results from this study indicate that A. bishopi parasitoids mainly rely on olfactory cues in host habitat location and that D-limonene and ocimene are the major attractants in infested fruit volatiles. These findings and the potential for manipulating A. bishopi for detection of infested fruit in the packhouse are discussed.
- Full Text:
- Date Issued: 2015
- Authors: Zimba, Kennedy J , Hill, Martin P , Moore, Sean D , Heshula, Unathi
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/423955 , vital:72108 , xlink:href="https://doi.org/10.1007/s10905-015-9526-0"
- Description: In South Africa, Thaumatotibia leucotreta is a key pest of citrus impacting its production and trade. Detection of newly infested fruit by visual inspection is challenging and poses a risk of packing infested with healthy fruit for export. Agathis bishopi is a larval endoparasitoid of T. leucotreta, attacking early larval instars. Understanding how A. bishopi parasitoids locate fruit infested with their host is of interest for developing an efficient detector for T. leucotreta infested fruit. The response of female adult A. bishopi parasitoids to olfactory and visual cues associated with T. leucotreta infested fruit were evaluated using a Y-tube olfactometer and flight tunnel. Agathis bishopi parasitoids were strongly attracted to infested fruit over healthy fruit, either when only olfactory or combinations of visual and olfactory cues were offered. Among the four synthetic compounds tested, D-limonene and ocimene elicited a strong attraction to parasitoids with response rates of 92 % and 72 % respectively. A blend of four synthetic compounds simulating T. leucotreta infested fruit odour equally elicited strong attraction to parasitoids (84 % response rate). Attraction of parasitoids to infested fruit cues was heightened by prior experience, suggesting the occurrence of associative learning. Results from this study indicate that A. bishopi parasitoids mainly rely on olfactory cues in host habitat location and that D-limonene and ocimene are the major attractants in infested fruit volatiles. These findings and the potential for manipulating A. bishopi for detection of infested fruit in the packhouse are discussed.
- Full Text:
- Date Issued: 2015
Agathis bishopi, a larval parasitoid of false codling moth Thaumatotibia leucotreta: laboratory rearing and effect of adult food on parasitism and longevity
- Zimba, Kennedy J, Moore, Sean D, Heshula, Lelethu U P, Hill, Martin P
- Authors: Zimba, Kennedy J , Moore, Sean D , Heshula, Lelethu U P , Hill, Martin P
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/406985 , vital:70328 , xlink:href="https://hdl.handle.net/10520/EJC185849"
- Description: Agathis bishopi (Nixon) (Hymenoptera: Braconidae) is a koinobiont larval endoparasitoid of false codling moth (FCM), Thaumatotibia leucotreta (Meyrick) (Lepidoptera: Tortricidae), a pest of economic importance on citrus in South Africa. In the field Agathis bishopi was found to parasitise up to 34 % of FCM larvae in fruit, reflecting reasonable biocontrol potential. Improving the rearing of A. bishopi would therefore complement the existing biocontrol strategies for FCM. In several parasitic wasps, sugar concentration and feeding duration has been shown to influence parasitism and longevity. However, their effect on parasitism and longevity of A. bishopi is unknown. In the present study a rearing protocol for A. bishopi is described, including evaluation of the effects of honey concentration on parasitoid longevity. On average, 18.2%of FCM larvae in rearing containers were parasitised under the rearing protocol described. Cotton wool, instead of paper towelling, as honey carrier for feeding parasitoids in rearing containers significantly increased parasitism and yield of offspring. Furthermore, longevity significantly increased with higher concentrations of honey. Maximum lifespan duration for male and female parasitoids was achieved when parasitoids were fed on 36 % (w/v) honey. Results from this study indicate that A. bishopi requires a sufficient concentration of sugar, coupled with frequent and prolonged feeding on a cotton wool substrate, in order to achieve maximum parasitism and longevity. Such information provides a basis for optimising mass-rearing and longevity of A. bishopi and parasitism of FCM in orchards.
- Full Text:
- Date Issued: 2015
- Authors: Zimba, Kennedy J , Moore, Sean D , Heshula, Lelethu U P , Hill, Martin P
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/406985 , vital:70328 , xlink:href="https://hdl.handle.net/10520/EJC185849"
- Description: Agathis bishopi (Nixon) (Hymenoptera: Braconidae) is a koinobiont larval endoparasitoid of false codling moth (FCM), Thaumatotibia leucotreta (Meyrick) (Lepidoptera: Tortricidae), a pest of economic importance on citrus in South Africa. In the field Agathis bishopi was found to parasitise up to 34 % of FCM larvae in fruit, reflecting reasonable biocontrol potential. Improving the rearing of A. bishopi would therefore complement the existing biocontrol strategies for FCM. In several parasitic wasps, sugar concentration and feeding duration has been shown to influence parasitism and longevity. However, their effect on parasitism and longevity of A. bishopi is unknown. In the present study a rearing protocol for A. bishopi is described, including evaluation of the effects of honey concentration on parasitoid longevity. On average, 18.2%of FCM larvae in rearing containers were parasitised under the rearing protocol described. Cotton wool, instead of paper towelling, as honey carrier for feeding parasitoids in rearing containers significantly increased parasitism and yield of offspring. Furthermore, longevity significantly increased with higher concentrations of honey. Maximum lifespan duration for male and female parasitoids was achieved when parasitoids were fed on 36 % (w/v) honey. Results from this study indicate that A. bishopi requires a sufficient concentration of sugar, coupled with frequent and prolonged feeding on a cotton wool substrate, in order to achieve maximum parasitism and longevity. Such information provides a basis for optimising mass-rearing and longevity of A. bishopi and parasitism of FCM in orchards.
- Full Text:
- Date Issued: 2015
Baculovirus-based strategies for the management of insect pests: a focus on development and application in South Africa
- Knox, Caroline M, Moore, Sean D, Luke, Garry, Hill, Martin P
- Authors: Knox, Caroline M , Moore, Sean D , Luke, Garry , Hill, Martin P
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/416829 , vital:71389 , xlink:href="https://doi.org/10.1080/09583157.2014.949222"
- Description: There is growing concern among governments, scientists, agricultural practitioners and the general public regarding the negative implications of widespread synthetic chemical pesticide application for the control of crop pests. As a result, baculovirus biopesticides are gaining popularity as components of integrated pest management (IPM) programmes in many countries despite several disadvantages related to slow speed of kill, limited host range and complex large scale production. In South Africa, baculoviruses are incorporated into IPM programmes for the control of crop pests in the field, and recent bioprospecting has led to the characterisation of several novel isolates with the potential to be formulated as commercial products. This contribution will provide an overview of the use of baculoviruses against insect pests in South Africa, as well as research and development efforts aimed at broadening their application as biocontrol agents. Challenges faced by researchers in developmental projects as well as potential users of baculoviruses as biopesticides in the field are also discussed.
- Full Text:
- Date Issued: 2015
- Authors: Knox, Caroline M , Moore, Sean D , Luke, Garry , Hill, Martin P
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/416829 , vital:71389 , xlink:href="https://doi.org/10.1080/09583157.2014.949222"
- Description: There is growing concern among governments, scientists, agricultural practitioners and the general public regarding the negative implications of widespread synthetic chemical pesticide application for the control of crop pests. As a result, baculovirus biopesticides are gaining popularity as components of integrated pest management (IPM) programmes in many countries despite several disadvantages related to slow speed of kill, limited host range and complex large scale production. In South Africa, baculoviruses are incorporated into IPM programmes for the control of crop pests in the field, and recent bioprospecting has led to the characterisation of several novel isolates with the potential to be formulated as commercial products. This contribution will provide an overview of the use of baculoviruses against insect pests in South Africa, as well as research and development efforts aimed at broadening their application as biocontrol agents. Challenges faced by researchers in developmental projects as well as potential users of baculoviruses as biopesticides in the field are also discussed.
- Full Text:
- Date Issued: 2015
Beauveria and Metarhizium against false codling moth (Lepidoptera: Tortricidae): a step towards selecting isolates for potential development of a mycoinsecticide
- Coombes, Candice A, Hill, Martin P, Moore, Sean D, Dames, Joanna F, Fullard, T
- Authors: Coombes, Candice A , Hill, Martin P , Moore, Sean D , Dames, Joanna F , Fullard, T
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/405757 , vital:70203 , xlink:href="https://hdl.handle.net/10520/EJC167505"
- Description: False codling moth, Thaumatotibia leucotreta Meyrick (1912) (Lepidoptera: Tortricidae), can cause both pre- and post-harvest damage to citrus fruit. Not only can this result in reduced crop yield, but more importantly because of the moth's endemism to sub-Saharan Africa, it is classified as a phytosanitary pest by many export markets. An entire consignment of citrus may be rejected in the presence of a single moth (Moore 2012). Since the bulk of citrus fruit production in South Africa is exported, the control of T. leucotreta is critical (Citrus Growers Association, South Africa 2012). Traditionally, control has been achieved through the use of chemical insecticides; however, residue restrictions, resistance development and concerns about environmental pollution have substantially reduced the dependence on chemical pesticides in citrus. Research on T. leucotreta control has therefore focused on the use of biological organisms (e.g. parasitoids and viruses), which are used as control agents within an integrated pest management (IPM) programme in citrus. These biological control agents, however, only targeted the aboveground life stages of the pest, not the soil-dwelling life stages (late fifth instars, prepupae, pupae), which is the subject of this contribution (Moore 2012).
- Full Text:
- Date Issued: 2015
- Authors: Coombes, Candice A , Hill, Martin P , Moore, Sean D , Dames, Joanna F , Fullard, T
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/405757 , vital:70203 , xlink:href="https://hdl.handle.net/10520/EJC167505"
- Description: False codling moth, Thaumatotibia leucotreta Meyrick (1912) (Lepidoptera: Tortricidae), can cause both pre- and post-harvest damage to citrus fruit. Not only can this result in reduced crop yield, but more importantly because of the moth's endemism to sub-Saharan Africa, it is classified as a phytosanitary pest by many export markets. An entire consignment of citrus may be rejected in the presence of a single moth (Moore 2012). Since the bulk of citrus fruit production in South Africa is exported, the control of T. leucotreta is critical (Citrus Growers Association, South Africa 2012). Traditionally, control has been achieved through the use of chemical insecticides; however, residue restrictions, resistance development and concerns about environmental pollution have substantially reduced the dependence on chemical pesticides in citrus. Research on T. leucotreta control has therefore focused on the use of biological organisms (e.g. parasitoids and viruses), which are used as control agents within an integrated pest management (IPM) programme in citrus. These biological control agents, however, only targeted the aboveground life stages of the pest, not the soil-dwelling life stages (late fifth instars, prepupae, pupae), which is the subject of this contribution (Moore 2012).
- Full Text:
- Date Issued: 2015
Comparisons of isotopic niche widths of some invasive and indigenous fauna in a South African river
- Hill, Jaclyn M, Jones, Roy W, Hill, Martin P, Weyl, Olaf L F
- Authors: Hill, Jaclyn M , Jones, Roy W , Hill, Martin P , Weyl, Olaf L F
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/423711 , vital:72088 , xlink:href="https://doi.org/10.1111/fwb.12542"
- Description: Biological invasions threaten ecosystem integrity and bio-diversity, with numerous adverse implications for native flora and fauna. Established populations of two notorious freshwater invaders, the snail Tarebia granifera and the fish Pterygoplichthys disjunctivus, have been reported on three continents and are frequently predicted to be in di-rect competition with native species for dietary resources.
- Full Text:
- Date Issued: 2015
- Authors: Hill, Jaclyn M , Jones, Roy W , Hill, Martin P , Weyl, Olaf L F
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/423711 , vital:72088 , xlink:href="https://doi.org/10.1111/fwb.12542"
- Description: Biological invasions threaten ecosystem integrity and bio-diversity, with numerous adverse implications for native flora and fauna. Established populations of two notorious freshwater invaders, the snail Tarebia granifera and the fish Pterygoplichthys disjunctivus, have been reported on three continents and are frequently predicted to be in di-rect competition with native species for dietary resources.
- Full Text:
- Date Issued: 2015
DNA-based identification of Lepidoptera associated with citrus in South Africa
- Marsberg, Tamryn, Hill, Martin P, Moore, Sean D, Timm, Alicia E
- Authors: Marsberg, Tamryn , Hill, Martin P , Moore, Sean D , Timm, Alicia E
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/405782 , vital:70205 , xlink:href="https://hdl.handle.net/10520/EJC167513"
- Description: A number of insects, primarily Lepidoptera, cause damage to citrus in South Africa. A major limitation to the management and control of these pests is their correct identification. The aim of this study was to develop a database of gene sequences to aid in the identification of these Lepidoptera. Multiple specimens of 12 species were sequenced for the ~650 bp of the cytochrome oxidase I gene. These sequence data were supplemented and validated using sequences available in public databases. Results showed that each species could be unambiguously identified, and neighbour-joining analysis based on K2P distances formed highly supported, distinct clusters for each species, i.e. the maximum intraspecific genetic distance was less than that of the minimum interspecific genetic distances. Thus, this data set provides a molecular means to successfully identify the most important Lepidoptera associated with citrus in South Africa.
- Full Text:
- Date Issued: 2015
- Authors: Marsberg, Tamryn , Hill, Martin P , Moore, Sean D , Timm, Alicia E
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/405782 , vital:70205 , xlink:href="https://hdl.handle.net/10520/EJC167513"
- Description: A number of insects, primarily Lepidoptera, cause damage to citrus in South Africa. A major limitation to the management and control of these pests is their correct identification. The aim of this study was to develop a database of gene sequences to aid in the identification of these Lepidoptera. Multiple specimens of 12 species were sequenced for the ~650 bp of the cytochrome oxidase I gene. These sequence data were supplemented and validated using sequences available in public databases. Results showed that each species could be unambiguously identified, and neighbour-joining analysis based on K2P distances formed highly supported, distinct clusters for each species, i.e. the maximum intraspecific genetic distance was less than that of the minimum interspecific genetic distances. Thus, this data set provides a molecular means to successfully identify the most important Lepidoptera associated with citrus in South Africa.
- Full Text:
- Date Issued: 2015
Genetic and biological characterisation of a novel Plutella xylostella granulovirus, PlxyGV-SA
- Abdulkadir, Fatima, Knox, Caroline M, Marsberg, Tamryn, Hill, Martin P, Moore, Sean D
- Authors: Abdulkadir, Fatima , Knox, Caroline M , Marsberg, Tamryn , Hill, Martin P , Moore, Sean D
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/417971 , vital:71498 , xlink:href="https://doi.org/10.1007/s10526-015-9666-3"
- Description: Plutella xylostella granulovirus (PlxyGV) has been isolated from insect populations in many countries and is considered a potential biopesticide for sustainable control of P. xylostella (L.) (Lepidoptera: Plutellidae). Several PlxyGV isolates have been genetically characterised, and the full genome sequence of PlxyGV-Japan is available for comparison with novel isolates. A South African PlxyGV was recently recovered from an overcrowded laboratory P. xylostella colony and identified as a genetically distinct isolate by sequencing of the granulin gene and restriction endonuclease (REN) analysis of genomic DNA. In this report, PlxyGV-SA was further characterised by PCR amplification and sequencing of egt, lef-8 and lef-9 genes, and several amino acid substitutions were observed. The PstI REN profile of PlxyGV-SA was different from that of PlxyGV-Japan in terms of band size and number, thereby confirming its novel genetic identity. Surface dose bioassays showed that PlxyGV-SA is pathogenic to neonate but not late instar larvae at the same and higher virus doses, indicating that a biopesticide should be targeted at early larval stages in the field.
- Full Text:
- Date Issued: 2015
- Authors: Abdulkadir, Fatima , Knox, Caroline M , Marsberg, Tamryn , Hill, Martin P , Moore, Sean D
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/417971 , vital:71498 , xlink:href="https://doi.org/10.1007/s10526-015-9666-3"
- Description: Plutella xylostella granulovirus (PlxyGV) has been isolated from insect populations in many countries and is considered a potential biopesticide for sustainable control of P. xylostella (L.) (Lepidoptera: Plutellidae). Several PlxyGV isolates have been genetically characterised, and the full genome sequence of PlxyGV-Japan is available for comparison with novel isolates. A South African PlxyGV was recently recovered from an overcrowded laboratory P. xylostella colony and identified as a genetically distinct isolate by sequencing of the granulin gene and restriction endonuclease (REN) analysis of genomic DNA. In this report, PlxyGV-SA was further characterised by PCR amplification and sequencing of egt, lef-8 and lef-9 genes, and several amino acid substitutions were observed. The PstI REN profile of PlxyGV-SA was different from that of PlxyGV-Japan in terms of band size and number, thereby confirming its novel genetic identity. Surface dose bioassays showed that PlxyGV-SA is pathogenic to neonate but not late instar larvae at the same and higher virus doses, indicating that a biopesticide should be targeted at early larval stages in the field.
- Full Text:
- Date Issued: 2015
Host searching and oviposition behaviour of Agathis bishopi (Hymenoptera: Braconidae), a larval parasitoid of false codling moth, Thaumatotibia leucotreta (Lepidoptera: Tortricidae): a potential proxy indicator for fruit infestation
- Zimba, Kennedy J, Heshula, Lelethu U P, Moore, Sean D, Hill, Martin P
- Authors: Zimba, Kennedy J , Heshula, Lelethu U P , Moore, Sean D , Hill, Martin P
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/407019 , vital:70330 , xlink:href="https://hdl.handle.net/10520/EJC195073"
- Description: Agathis bishopi (Nixon) (Hymenoptera: Braconidae)is an arrhenotokous larval endoparasitoid of Thaumatotibia leucotreta (Meyrick) (Lepidoptera: Tortricidae) (Gendall 2007; Hofmeyr et al. 2015) commonly known as false codling moth (FCM), a major pest of citrus in South Africa (Moore et al. 2004; Malan et al. 2011). Under field conditions, A. bishopi was identified attacking more than 34% of FCM larvae in fruit, showing good biocontrol potential (Gendall 2007). Preference by A. bishopi for parasitising the early instars of its concealed host suggests that the parasitoid has strong natural host location ability (Sishuba 2003; Gendall 2007).
- Full Text:
- Date Issued: 2015
- Authors: Zimba, Kennedy J , Heshula, Lelethu U P , Moore, Sean D , Hill, Martin P
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/407019 , vital:70330 , xlink:href="https://hdl.handle.net/10520/EJC195073"
- Description: Agathis bishopi (Nixon) (Hymenoptera: Braconidae)is an arrhenotokous larval endoparasitoid of Thaumatotibia leucotreta (Meyrick) (Lepidoptera: Tortricidae) (Gendall 2007; Hofmeyr et al. 2015) commonly known as false codling moth (FCM), a major pest of citrus in South Africa (Moore et al. 2004; Malan et al. 2011). Under field conditions, A. bishopi was identified attacking more than 34% of FCM larvae in fruit, showing good biocontrol potential (Gendall 2007). Preference by A. bishopi for parasitising the early instars of its concealed host suggests that the parasitoid has strong natural host location ability (Sishuba 2003; Gendall 2007).
- Full Text:
- Date Issued: 2015