The influence of citrus orchard age on the ecology of entomopathogenic fungi and nematodes
- Albertyn ,Sonnica, Moore, Sean D, Marsberg, Tamryn, Coombes, Candice A, Hill, Martin P
- Authors: Albertyn ,Sonnica , Moore, Sean D , Marsberg, Tamryn , Coombes, Candice A , Hill, Martin P
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/417545 , vital:71462 , xlink:href="https://hdl.handle.net/10520/ejc-cristal-v10-n1-a7"
- Description: A three-year survey of the ecology of entomopathogenic nematodes (EPN) and entomopathogenic fungi (EPF) was undertaken on soils from citrus orchards of different ages to determine the influence of orchard age on the ecology of entomopathogenic fungi and nematodes. The influence of mulch and irrigation method on the occurrence of EPN and EPF was also determined. Most of the isolates recovered (n = 810) were Beauveria sp. (87.88% of all isolates), followed by Metarhizium sp. (11.87% of all isolates). Only 0.24% of soil samples collected during this study tested positive for EPN. All EPN isolates recovered were Heterorhabditis bacteriophora. No significant differences in EPF occurrence were recorded between orchards under drip and micro-sprinkler irrigation. EPF occurrence was significantly lower (P = 0.016) in orchards covered by mulch (31.85% ± 2.07% occurrence) than in orchards with no covering (38.57% ± 1.57% occurrence). EPF occurrence of 40.33 ± 2.13% was highest in non-bearing orchards, followed by mature orchards (nine years or older) (36.76 ± 2.05% of samples) with the lowest EPF occurrence of 25.30 ± 2.02% reported in juvenile orchards (four to eight years old). Juvenile orchards sustain significantly less EPF than mature and non-bearing orchards because of the combined negative impact of less favourable environmental conditions (lower shade density) and fungicide applications.
- Full Text:
- Date Issued: 2020
- Authors: Albertyn ,Sonnica , Moore, Sean D , Marsberg, Tamryn , Coombes, Candice A , Hill, Martin P
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/417545 , vital:71462 , xlink:href="https://hdl.handle.net/10520/ejc-cristal-v10-n1-a7"
- Description: A three-year survey of the ecology of entomopathogenic nematodes (EPN) and entomopathogenic fungi (EPF) was undertaken on soils from citrus orchards of different ages to determine the influence of orchard age on the ecology of entomopathogenic fungi and nematodes. The influence of mulch and irrigation method on the occurrence of EPN and EPF was also determined. Most of the isolates recovered (n = 810) were Beauveria sp. (87.88% of all isolates), followed by Metarhizium sp. (11.87% of all isolates). Only 0.24% of soil samples collected during this study tested positive for EPN. All EPN isolates recovered were Heterorhabditis bacteriophora. No significant differences in EPF occurrence were recorded between orchards under drip and micro-sprinkler irrigation. EPF occurrence was significantly lower (P = 0.016) in orchards covered by mulch (31.85% ± 2.07% occurrence) than in orchards with no covering (38.57% ± 1.57% occurrence). EPF occurrence of 40.33 ± 2.13% was highest in non-bearing orchards, followed by mature orchards (nine years or older) (36.76 ± 2.05% of samples) with the lowest EPF occurrence of 25.30 ± 2.02% reported in juvenile orchards (four to eight years old). Juvenile orchards sustain significantly less EPF than mature and non-bearing orchards because of the combined negative impact of less favourable environmental conditions (lower shade density) and fungicide applications.
- Full Text:
- Date Issued: 2020
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
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
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
Morphological and genetic characterization of a South African Plutella xylostella granulovirus (plxy GV) isolate
- Abdulkadir, Fatima, Marsberg, Tamryn, Knox, Caroline M, Hill, Martin P, Moore, Sean D
- Authors: Abdulkadir, Fatima , Marsberg, Tamryn , Knox, Caroline M , Hill, Martin P , Moore, Sean D
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/406117 , vital:70240 , xlink:href="https://hdl.handle.net/10520/EJC132828"
- Description: Plutella xylostella (L.) (Lepidoptera: Plutellidae), also known as diamondback moth, is a destructive insect pest of cruciferous crops (Talekar and Shelton 1993; Shelton 2004). The pest occurs wherever its host plants are cultivated and the global annual cost of damage and control is estimated to be US$4-5 billion (Zalucki et al. 2012). The extensive use of synthetic pesticides for control combined with the high fecundity of P. xylostella has resulted in the pest developing resistance to nearly all classes of insecticides (Grzywacz et al. 2009). Moreover, these chemicals have negative environmental implications and may affect non-target species, some of which are natural enemies of the pest.
- Full Text:
- Date Issued: 2013
- Authors: Abdulkadir, Fatima , Marsberg, Tamryn , Knox, Caroline M , Hill, Martin P , Moore, Sean D
- Date: 2013
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/406117 , vital:70240 , xlink:href="https://hdl.handle.net/10520/EJC132828"
- Description: Plutella xylostella (L.) (Lepidoptera: Plutellidae), also known as diamondback moth, is a destructive insect pest of cruciferous crops (Talekar and Shelton 1993; Shelton 2004). The pest occurs wherever its host plants are cultivated and the global annual cost of damage and control is estimated to be US$4-5 billion (Zalucki et al. 2012). The extensive use of synthetic pesticides for control combined with the high fecundity of P. xylostella has resulted in the pest developing resistance to nearly all classes of insecticides (Grzywacz et al. 2009). Moreover, these chemicals have negative environmental implications and may affect non-target species, some of which are natural enemies of the pest.
- Full Text:
- Date Issued: 2013
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