An improved systems approach as a phytosanitary measure for Thaumatotibia leucotreta (Lepidoptera: Tortricidae) in export citrus fruit from South Africa
- Hattingh, Vaughan, Moore, Sean D, Kirkman, Wayne, Goddard, Mathew K, Thackeray, Sean R, Peyper, Mellissa, Sharp, Gary, Cronjé, Paul, Pringle, Ken
- Authors: Hattingh, Vaughan , Moore, Sean D , Kirkman, Wayne , Goddard, Mathew K , Thackeray, Sean R , Peyper, Mellissa , Sharp, Gary , Cronjé, Paul , Pringle, Ken
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/423700 , vital:72086 , xlink:href="https://doi.org/10.1093/jee/toz336"
- Description: A systems approach was previously developed for mitigating phytosanitary risk of Thaumatotibia leucotreta (Meyrick) in citrus fruit exported from South Africa, as an alternative to a standalone cold disinfestation treatment. The present study first tested the original systems approach by applying it on a semicommercial scale in 10 Nova mandarin orchards. Fruit were inspected at points in the production, packing, and simulated shipping process, to assess performance of the systems approach. Additional data were obtained from 17 Valencia orange orchards and six packinghouses. In the second part of this study, the systems approach was accordingly revised and improved, consisting of three measures: 1) preharvest controls and measurements and postpicking sampling, inspection, and packinghouse procedures; 2) postpacking sampling and inspection; and 3) shipping conditions. The model quantifying the effectiveness of the systems approach was improved by correcting errors in the original version, updating parameter values and adding a component that provides for comparison with the risk mitigation provided by a standalone disinfestation treatment. Consequently, the maximum potential proportion of fruit that may be infested with live T. leucotreta after application of the improved systems approach is no greater than the proportion of fruit that may be infested after application of a Probit 9 efficacy postharvest disinfestation treatment to fruit with a 2% pretreatment infestation. The probability of a mating pair surviving is also determined. The model enables a priori determination of the required threshold levels for any of the three measures, based on quantification of the other two measures.
- Full Text:
- Date Issued: 2020
- Authors: Hattingh, Vaughan , Moore, Sean D , Kirkman, Wayne , Goddard, Mathew K , Thackeray, Sean R , Peyper, Mellissa , Sharp, Gary , Cronjé, Paul , Pringle, Ken
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/423700 , vital:72086 , xlink:href="https://doi.org/10.1093/jee/toz336"
- Description: A systems approach was previously developed for mitigating phytosanitary risk of Thaumatotibia leucotreta (Meyrick) in citrus fruit exported from South Africa, as an alternative to a standalone cold disinfestation treatment. The present study first tested the original systems approach by applying it on a semicommercial scale in 10 Nova mandarin orchards. Fruit were inspected at points in the production, packing, and simulated shipping process, to assess performance of the systems approach. Additional data were obtained from 17 Valencia orange orchards and six packinghouses. In the second part of this study, the systems approach was accordingly revised and improved, consisting of three measures: 1) preharvest controls and measurements and postpicking sampling, inspection, and packinghouse procedures; 2) postpacking sampling and inspection; and 3) shipping conditions. The model quantifying the effectiveness of the systems approach was improved by correcting errors in the original version, updating parameter values and adding a component that provides for comparison with the risk mitigation provided by a standalone disinfestation treatment. Consequently, the maximum potential proportion of fruit that may be infested with live T. leucotreta after application of the improved systems approach is no greater than the proportion of fruit that may be infested after application of a Probit 9 efficacy postharvest disinfestation treatment to fruit with a 2% pretreatment infestation. The probability of a mating pair surviving is also determined. The model enables a priori determination of the required threshold levels for any of the three measures, based on quantification of the other two measures.
- 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
Partial cold treatment of citrus fruit for export risk mitigation for Thaumatotibia leucotreta (Lepidoptera: Tortricidae) as part of a systems approach
- Moore, Sean D, Kirkman, Wayne, Albertyn, Sonnica, Love, C N, Coetzee, Julie A, Hattingh, Vaughan
- Authors: Moore, Sean D , Kirkman, Wayne , Albertyn, Sonnica , Love, C N , Coetzee, Julie A , Hattingh, Vaughan
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/423796 , vital:72094 , xlink:href="https://doi.org/10.1093/jee/tow138"
- Description: Some of South Africa’s citrus export markets require mandatory postharvest cold treatment of citrus fruit as a phytosanitary risk mitigation treatment for Thaumatotibia leucotreta (Meyrick) (Lepidoptera: Tortricidae). An alternative to this may be partial cold treatment as one of the final steps in a systems approach to mitigate phytosanitary risk. Consequently, the efficacy of such partial cold treatments was evaluated. It was first determined that a 2C cold treatment was significantly more effective against fourth and fifth instars (the most cold-tolerant instars) than treatments at 3C and 4C for a duration of 18 d. Secondly, it was determined that 2C for 18 d and 1C for 16 d were similarly effective, but both treatments were significantly more effective than 1C for 14 d. Mean mortality of fourth and fifth instars treated with 2C for 18 d in seven replicates from four trials was 99.94%. Finally, it was determined that the inability of the majority of surviving larvae to develop to adulthood would further increase the efficacy of a 2C for 18 d treatment to 99.96%. Inclusion of reproductive nonviability of survivors increased mortality to 99.99%.
- Full Text:
- Date Issued: 2016
- Authors: Moore, Sean D , Kirkman, Wayne , Albertyn, Sonnica , Love, C N , Coetzee, Julie A , Hattingh, Vaughan
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/423796 , vital:72094 , xlink:href="https://doi.org/10.1093/jee/tow138"
- Description: Some of South Africa’s citrus export markets require mandatory postharvest cold treatment of citrus fruit as a phytosanitary risk mitigation treatment for Thaumatotibia leucotreta (Meyrick) (Lepidoptera: Tortricidae). An alternative to this may be partial cold treatment as one of the final steps in a systems approach to mitigate phytosanitary risk. Consequently, the efficacy of such partial cold treatments was evaluated. It was first determined that a 2C cold treatment was significantly more effective against fourth and fifth instars (the most cold-tolerant instars) than treatments at 3C and 4C for a duration of 18 d. Secondly, it was determined that 2C for 18 d and 1C for 16 d were similarly effective, but both treatments were significantly more effective than 1C for 14 d. Mean mortality of fourth and fifth instars treated with 2C for 18 d in seven replicates from four trials was 99.94%. Finally, it was determined that the inability of the majority of surviving larvae to develop to adulthood would further increase the efficacy of a 2C for 18 d treatment to 99.96%. Inclusion of reproductive nonviability of survivors increased mortality to 99.99%.
- Full Text:
- Date Issued: 2016
The effect of long-distance transportation on the fitness of irradiated false codling Moth (Lepidoptera: Tortricidae) for use in a sterile insect release program
- Nepgen, Eugene S, Hill, Martin P, Moore, Sean D
- Authors: Nepgen, Eugene S , Hill, Martin P , Moore, Sean D
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/423835 , vital:72098 , xlink:href="https://doi.org/10.1093/jee/tov246"
- Description: The effect of cold immobilization and long-distance transport of irradiated Thaumatotibia leucotreta (Meyrick) on the flight ability of male (?) and female (/) moths, the longevity of male and female moths, and the realized fecundity of mating pairs CIM (chilled irradiated moths) / CIM?, CIM/ NIP (nonirradiated pupae) ?, NIP/ CIM?, and NIP/ NIP? was examined to improve application of the sterile insect technique (SIT). Adult moths treated with 150 Gy of gamma radiation were immobilized with cold temperature between 4 and 6C inside a polyurethane cooler box and transported for 12 h by road from Citrusdal, Western Cape Province, to Addo, Eastern Cape Province. Nonirradiated moths were transported as pupae inside a cardboard tray and removed by hand after which male and female pupae were separated and placed inside containers for eclosion. Male and female moths were individually placed inside petri dishes to determine longevity or paired with irradiated and nonirradiated counterparts to evaluate realized fecundity before incubation in 100% darkness at 25C and 75% relative humidity. Flight tests were conducted indoors at 25C by release of individual moths per hand. A significant decrease in flight ability and longevity of irradiated false codling moth was found after handling, cold immobilization, and transport, although critically, realized fecundity was not affected. Because of the impact of long-distance transport on quality of the released insects as well as the efficacy of SIT, comprehensive protocols for this critical step in the process need to be developed for a pestiferous insect with phytosanitary status such as false codling moth.
- Full Text:
- Date Issued: 2015
- Authors: Nepgen, Eugene S , Hill, Martin P , Moore, Sean D
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/423835 , vital:72098 , xlink:href="https://doi.org/10.1093/jee/tov246"
- Description: The effect of cold immobilization and long-distance transport of irradiated Thaumatotibia leucotreta (Meyrick) on the flight ability of male (?) and female (/) moths, the longevity of male and female moths, and the realized fecundity of mating pairs CIM (chilled irradiated moths) / CIM?, CIM/ NIP (nonirradiated pupae) ?, NIP/ CIM?, and NIP/ NIP? was examined to improve application of the sterile insect technique (SIT). Adult moths treated with 150 Gy of gamma radiation were immobilized with cold temperature between 4 and 6C inside a polyurethane cooler box and transported for 12 h by road from Citrusdal, Western Cape Province, to Addo, Eastern Cape Province. Nonirradiated moths were transported as pupae inside a cardboard tray and removed by hand after which male and female pupae were separated and placed inside containers for eclosion. Male and female moths were individually placed inside petri dishes to determine longevity or paired with irradiated and nonirradiated counterparts to evaluate realized fecundity before incubation in 100% darkness at 25C and 75% relative humidity. Flight tests were conducted indoors at 25C by release of individual moths per hand. A significant decrease in flight ability and longevity of irradiated false codling moth was found after handling, cold immobilization, and transport, although critically, realized fecundity was not affected. Because of the impact of long-distance transport on quality of the released insects as well as the efficacy of SIT, comprehensive protocols for this critical step in the process need to be developed for a pestiferous insect with phytosanitary status such as false codling moth.
- Full Text:
- Date Issued: 2015
Trophic ecology of zooplankton at a frontal transition zone: fatty acid signatures at the subtropical convergence, Southern Ocean
- Authors: Richoux, Nicole B
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/458033 , vital:75711 , xlink:href="https://doi.org/10.1093/plankt/fbq132"
- Description: Regional variations in fatty acid composition were assessed in zooplankton communities situated immediately north and south of the subtropical convergence (STC), where warm (maximum 21°C) nutrient-poor waters of the southwest Indian Ocean converge with cool (minimum 11°C) nutrient-rich subantarctic waters of the Southern Ocean. I hypothesized that food web structures differ from north to south based on average spatial differences in primary productivity, and that zooplankton in the more productive region show enhanced herbivorous feeding. Several taxonomic groups including euphausiids showed differences in their fatty acid signatures from north to south, indicating the existence of measurable within- and among-species differences in trophic relationships between the two communities, presumably stemming from variations in food quality and availability. The indices 22:6ω3/20:5ω3, 18:1ω9/18:1ω7 and Σω3/Σω6 indicated that carnivory was the dominant feeding mode in the north, whereas herbivory was more prevalent in the south, a pattern that was not detected in the same region using stable isotope ratios. Such conflicting results substantiate the importance of utilizing more than one method to investigate feeding relationships in aquatic systems. Fatty acid profiles of the amphipod Themisto gaudichaudii revealed some distinct herbivory markers, indicating more complex feeding habits by this important pelagic species than previously reported. My findings shed new light on the regional variations in zooplankton diet and food web dynamics in a poorly understood but critically important frontal zone bordering the Southern Ocean.
- Full Text:
- Date Issued: 2011
- Authors: Richoux, Nicole B
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/458033 , vital:75711 , xlink:href="https://doi.org/10.1093/plankt/fbq132"
- Description: Regional variations in fatty acid composition were assessed in zooplankton communities situated immediately north and south of the subtropical convergence (STC), where warm (maximum 21°C) nutrient-poor waters of the southwest Indian Ocean converge with cool (minimum 11°C) nutrient-rich subantarctic waters of the Southern Ocean. I hypothesized that food web structures differ from north to south based on average spatial differences in primary productivity, and that zooplankton in the more productive region show enhanced herbivorous feeding. Several taxonomic groups including euphausiids showed differences in their fatty acid signatures from north to south, indicating the existence of measurable within- and among-species differences in trophic relationships between the two communities, presumably stemming from variations in food quality and availability. The indices 22:6ω3/20:5ω3, 18:1ω9/18:1ω7 and Σω3/Σω6 indicated that carnivory was the dominant feeding mode in the north, whereas herbivory was more prevalent in the south, a pattern that was not detected in the same region using stable isotope ratios. Such conflicting results substantiate the importance of utilizing more than one method to investigate feeding relationships in aquatic systems. Fatty acid profiles of the amphipod Themisto gaudichaudii revealed some distinct herbivory markers, indicating more complex feeding habits by this important pelagic species than previously reported. My findings shed new light on the regional variations in zooplankton diet and food web dynamics in a poorly understood but critically important frontal zone bordering the Southern Ocean.
- Full Text:
- Date Issued: 2011
Plankton trophodynamics at the subtropical convergence, Southern Ocean
- Richoux, Nicole B, Froneman, P William
- Authors: Richoux, Nicole B , Froneman, P William
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/457967 , vital:75704 , xlink:href="https://doi.org/10.1093/plankt/fbp054"
- Description: Stable isotope signatures (δ13C, δ15N) in zooplankton tissues and particulate organic matter (POM) were determined to assess regional differences in the trophodynamics of zooplankton communities between 38 and 43°S, where the cool nutrient-rich subantarctic waters of the Southern Ocean meet the warm nutrient-poor subtropical waters of the southwest Indian Ocean at the subtropical convergence (STC). Significantly enriched values of δ15N were noted in populations of all major zooplankton groups inhabiting the warm and saline water mass north of the STC (maximum surface temperature 21°C), including the euphausiids, salps, amphipods, copepods, ostracods, pyrosomes, pteropods and chaetognaths, compared with those in the cool, less saline southern water mass (minimum surface temperature 11°C). Similar patterns of δ15N in POM collected throughout the region suggest that the large changes in zooplankton δ15N values across the frontal region are driven by variations in the phytoplankton communities. The differing trophodynamics in communities north and south of the STC provide compelling evidence of distinct bottom-up effects on planktonic food webs which have important implications in the determination of trophic positions and motility of plankton and higher consumers using δ15N signatures. Although expected, similar latitudinal variations in δ13C signatures were not found.
- Full Text:
- Date Issued: 2009
- Authors: Richoux, Nicole B , Froneman, P William
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/457967 , vital:75704 , xlink:href="https://doi.org/10.1093/plankt/fbp054"
- Description: Stable isotope signatures (δ13C, δ15N) in zooplankton tissues and particulate organic matter (POM) were determined to assess regional differences in the trophodynamics of zooplankton communities between 38 and 43°S, where the cool nutrient-rich subantarctic waters of the Southern Ocean meet the warm nutrient-poor subtropical waters of the southwest Indian Ocean at the subtropical convergence (STC). Significantly enriched values of δ15N were noted in populations of all major zooplankton groups inhabiting the warm and saline water mass north of the STC (maximum surface temperature 21°C), including the euphausiids, salps, amphipods, copepods, ostracods, pyrosomes, pteropods and chaetognaths, compared with those in the cool, less saline southern water mass (minimum surface temperature 11°C). Similar patterns of δ15N in POM collected throughout the region suggest that the large changes in zooplankton δ15N values across the frontal region are driven by variations in the phytoplankton communities. The differing trophodynamics in communities north and south of the STC provide compelling evidence of distinct bottom-up effects on planktonic food webs which have important implications in the determination of trophic positions and motility of plankton and higher consumers using δ15N signatures. Although expected, similar latitudinal variations in δ13C signatures were not found.
- Full Text:
- Date Issued: 2009
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