Investigation of the larval parasitoids of the false codling moth, Cryptophlebia Leucotreta (Meyrick) (Lepidoptera: Tortricidae), on citrus in South Africa
- Authors: Sishuba, Nomahlubi
- Date: 2004
- Subjects: Cryptophlebia leucotreta , Tortricidae , Cryptophlebia leucotreta -- Control , Pests -- Biological control , Parasitoids , Citrus -- Diseases and pests
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5918 , http://hdl.handle.net/10962/d1016267
- Description: The study examined the larval parasitoids of Cryptophlebia leucotreta (Meyrick) on citrus in South Africa and aimed to improve the existing rearing techniques of C. leucotreta with a view to mass rearing of biological control agents. The biological characteristics of Agathis bishopi Nixon (Hymenoptera: Braconidae) were studied, with an emphasis on parasitism rates in the field, host stage preference, developmental rate, life span and offspring sex ratios. Two larval parasitoids, A. bishopi and Apophua leucotretae (Wilkinson) (Hymenoptera: Ichneumonidae), and an egg parasitoid, Trichogrammatoidea cryptophlebiae Nagaraja (Hymenoptera: Trichogrammatidae), were recorded on C. leucotreta on citrus. A. bishopi was the more abundant of the larval parasitoids and exhibited density dependent parasitism. The highest parasitism rates were observed in December with up to 38% in Sundays River Valley and 34% in Gamtoos River Valley, at a time when the highest false codling moth infestations were observed. Agathis bishopi was recorded only in the Eastern Cape Province. The sex ratio of A. bishopi was biased towards females throughout the study (77% in Gamtoos River Valley and 72% in Sundays River Valley). Agathis bishopi is a solitary, koinobiont, larval-pupal endoparasitoid. The species showed a preference for 1st and 2"d instar hosts. Females regulate the sex of their progeny according to the size and larval stage of the host, ovipositing unfertilised eggs in younger, smaller larvae (1st instars) and fertilised eggs in older, larger larvae (2nd instars). The developmental rate of A. bishopi is in synchrony with that of the moth and adults emerge when adult moths that have escaped parasitism emerge. Agathis bishopi and T. cryptophlebiae compliment each other because they have different niches and strategies of attack. Integrating A. bishopi and T. cryptophlebiae into the management of citrus orchards has potential to suppress false codling moth. Larger rearing containers seemed ideal for large-scale rearing of false codling moth. A higher percentage of adults was obtained from larvae reared in larger containers than in smaller ones. The width of the sponges used as stoppers prevented escape of the larvae. Media prepared in larger containers are easier and simpler to prepare than in smaller ones, thus eliminating many precautions otherwise necessary to prevent contamination. Moth production was greatly reduced by the high concentration of Sporekill used for egg decontamination.
- Full Text:
- Date Issued: 2004
- Authors: Sishuba, Nomahlubi
- Date: 2004
- Subjects: Cryptophlebia leucotreta , Tortricidae , Cryptophlebia leucotreta -- Control , Pests -- Biological control , Parasitoids , Citrus -- Diseases and pests
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5918 , http://hdl.handle.net/10962/d1016267
- Description: The study examined the larval parasitoids of Cryptophlebia leucotreta (Meyrick) on citrus in South Africa and aimed to improve the existing rearing techniques of C. leucotreta with a view to mass rearing of biological control agents. The biological characteristics of Agathis bishopi Nixon (Hymenoptera: Braconidae) were studied, with an emphasis on parasitism rates in the field, host stage preference, developmental rate, life span and offspring sex ratios. Two larval parasitoids, A. bishopi and Apophua leucotretae (Wilkinson) (Hymenoptera: Ichneumonidae), and an egg parasitoid, Trichogrammatoidea cryptophlebiae Nagaraja (Hymenoptera: Trichogrammatidae), were recorded on C. leucotreta on citrus. A. bishopi was the more abundant of the larval parasitoids and exhibited density dependent parasitism. The highest parasitism rates were observed in December with up to 38% in Sundays River Valley and 34% in Gamtoos River Valley, at a time when the highest false codling moth infestations were observed. Agathis bishopi was recorded only in the Eastern Cape Province. The sex ratio of A. bishopi was biased towards females throughout the study (77% in Gamtoos River Valley and 72% in Sundays River Valley). Agathis bishopi is a solitary, koinobiont, larval-pupal endoparasitoid. The species showed a preference for 1st and 2"d instar hosts. Females regulate the sex of their progeny according to the size and larval stage of the host, ovipositing unfertilised eggs in younger, smaller larvae (1st instars) and fertilised eggs in older, larger larvae (2nd instars). The developmental rate of A. bishopi is in synchrony with that of the moth and adults emerge when adult moths that have escaped parasitism emerge. Agathis bishopi and T. cryptophlebiae compliment each other because they have different niches and strategies of attack. Integrating A. bishopi and T. cryptophlebiae into the management of citrus orchards has potential to suppress false codling moth. Larger rearing containers seemed ideal for large-scale rearing of false codling moth. A higher percentage of adults was obtained from larvae reared in larger containers than in smaller ones. The width of the sponges used as stoppers prevented escape of the larvae. Media prepared in larger containers are easier and simpler to prepare than in smaller ones, thus eliminating many precautions otherwise necessary to prevent contamination. Moth production was greatly reduced by the high concentration of Sporekill used for egg decontamination.
- Full Text:
- Date Issued: 2004
Geographic variation in the susceptibility of false colding Moth, Thaumatotibia Leucotreta, populations to a granulovirus (CrleGV-SA)
- Authors: Opoku-Debrah, John Kwadwo
- Date: 2008
- Subjects: Cryptophlebia leucotreta , Cryptophlebia leucotreta -- Control , Pests -- Biological control , Citrus -- Diseases and pests
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:10586 , http://hdl.handle.net/10948/984 , Cryptophlebia leucotreta , Cryptophlebia leucotreta -- Control , Pests -- Biological control , Citrus -- Diseases and pests
- Description: The false codling moth (FCM), Thaumatotibia (=Cryptophlebia) leucotreta (Meyrick) (Lepidoptera: Tortricidae) is a serious pest of citrus and other crops in Sub-Saharan Africa. The introduction of the Cryptophlebia leucotreta granulovirus (CrleGV-SA) Cryptogran and Cryptex (biopesticides) has proven to be very effective in the control of FCM. However, markedly lower susceptibility of some codling moth (CM), Cydia pomonella (L.) populations to Cydia pomonella granulovirus (CpGV-M), another granulovirus product used in the control of CM’s in Europe have been reported. Genetic differences between FCM populations in South Africa have also been established. It is therefore possible that differences in the susceptibility of these geographically distinct FCM populations to CrleGV-SA might also exist. To investigate this phenomenon, a benchmark for pathogenecity was established. In continuation of previous work with Cryptogran against the 1st and 5th instar FCM larvae, dose-response relationships were established for all five larval instars of FCM. In surface dose-response bioassays, the LC50 values for the 2nd, 3rd and 4th instars were calculated to be 4.516 x 104, 1.662 x 105 and 2.205 x 106 occlusion bodies (OBs)/ml, respectively. The LC90 values for the 2nd, 3rd and 4th instars were calculated to be 4.287 x 106, 9.992 x 106 and 1.661 x 108 OBs/ml, respectively. Susceptibility to CrleGV-SA was found to decline with larval stage and increase with time of exposure. The protocol was used in guiding bioassays with field collected FCM larvae. Laboratory assays conducted with Cryptogran (at 1.661 x 108 OBs/ml) against field collected FCM larvae from Addo, Kirkwood, Citrusdal and Clanwilliam as well as a standard laboratory colony, showed a significant difference in pathogenecity in only one case. This significant difference was observed between 5th instars from the Addo colony and 5th instars from the other populations. Four geographically distinct FCM colonies from Addo, Citrusdal, Marble Hall and Nelspruit were also established. Since Cryptogran and Cryptex are always targeted against 1st instar FCM larvae in the field, further comparative laboratory assays were conducted with the Addo colony and an old laboratory colony. Cryptogran was significantly more pathogenic than Cryptex against both the Addo and the old colony. However, a high level of heterogeneity was observed in responses within each population.
- Full Text:
- Date Issued: 2008
- Authors: Opoku-Debrah, John Kwadwo
- Date: 2008
- Subjects: Cryptophlebia leucotreta , Cryptophlebia leucotreta -- Control , Pests -- Biological control , Citrus -- Diseases and pests
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:10586 , http://hdl.handle.net/10948/984 , Cryptophlebia leucotreta , Cryptophlebia leucotreta -- Control , Pests -- Biological control , Citrus -- Diseases and pests
- Description: The false codling moth (FCM), Thaumatotibia (=Cryptophlebia) leucotreta (Meyrick) (Lepidoptera: Tortricidae) is a serious pest of citrus and other crops in Sub-Saharan Africa. The introduction of the Cryptophlebia leucotreta granulovirus (CrleGV-SA) Cryptogran and Cryptex (biopesticides) has proven to be very effective in the control of FCM. However, markedly lower susceptibility of some codling moth (CM), Cydia pomonella (L.) populations to Cydia pomonella granulovirus (CpGV-M), another granulovirus product used in the control of CM’s in Europe have been reported. Genetic differences between FCM populations in South Africa have also been established. It is therefore possible that differences in the susceptibility of these geographically distinct FCM populations to CrleGV-SA might also exist. To investigate this phenomenon, a benchmark for pathogenecity was established. In continuation of previous work with Cryptogran against the 1st and 5th instar FCM larvae, dose-response relationships were established for all five larval instars of FCM. In surface dose-response bioassays, the LC50 values for the 2nd, 3rd and 4th instars were calculated to be 4.516 x 104, 1.662 x 105 and 2.205 x 106 occlusion bodies (OBs)/ml, respectively. The LC90 values for the 2nd, 3rd and 4th instars were calculated to be 4.287 x 106, 9.992 x 106 and 1.661 x 108 OBs/ml, respectively. Susceptibility to CrleGV-SA was found to decline with larval stage and increase with time of exposure. The protocol was used in guiding bioassays with field collected FCM larvae. Laboratory assays conducted with Cryptogran (at 1.661 x 108 OBs/ml) against field collected FCM larvae from Addo, Kirkwood, Citrusdal and Clanwilliam as well as a standard laboratory colony, showed a significant difference in pathogenecity in only one case. This significant difference was observed between 5th instars from the Addo colony and 5th instars from the other populations. Four geographically distinct FCM colonies from Addo, Citrusdal, Marble Hall and Nelspruit were also established. Since Cryptogran and Cryptex are always targeted against 1st instar FCM larvae in the field, further comparative laboratory assays were conducted with the Addo colony and an old laboratory colony. Cryptogran was significantly more pathogenic than Cryptex against both the Addo and the old colony. However, a high level of heterogeneity was observed in responses within each population.
- Full Text:
- Date Issued: 2008
Understanding and improving the residual efficacy of the cryptophlebia leucotreta granulovirus (Cryptogran)
- Authors: Kirkman, Wayne
- Date: 2008
- Subjects: Cryptophlebia leucotreta , Cryptophlebia leucotreta -- Control , Pests -- Biological control , Citrus -- Diseases and pests
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5794 , http://hdl.handle.net/10962/d1005482 , Cryptophlebia leucotreta , Cryptophlebia leucotreta -- Control , Pests -- Biological control , Citrus -- Diseases and pests
- Description: False codling moth (FCM), Thaumatotibia (=Cryptophlebia) leucotreta (Meyr) (Lepidoptera: Tortricidae), is one of the most important pests on citrus. The Cryptophlebia leucotreta granulovirus (CrleGV) has been developed into a successful biological control agent, registered under the name Cryptogran, and is currently the preferred product for the control of FCM on citrus in South Africa. A prerequisite to the continued success of Cryptogran as a means of controlling false codling moth is to understand the factors affecting field persistence of the virus, and to find ways to improve it. The aim of this study was to gain a clearer understanding of the product and the abiotic and biotic factors affecting its persistence in the field, and to investigate methods to improve this persistence. The effect of UV-irradiation on the virus was determined, and various products were tested as UV protectants in laboratory bioassays. Lignin was the most effective additive, and was tested in several field trials, where it also enhanced the efficacy of Cryptogran. Laboratory trials indicated that Cryptogran is rainfast. Cryptogran applications early in the season had a longer period of residual activity than sprays applied closer to harvest. Daytime applications were less effective that evening sprays. Sprays applied coinciding with peaks in pheromone moth trap catches were more effective than those applied between peaks. Biotic factors influencing persistence were investigated. Residual efficacy was longer when treatments were applied to blocks than as single tree treatments. Attempts were made to quantify the effect of the navel end of a navel orange on the field persistence of Cryptogran. Cryptogran was shown to be compatible with many agricultural chemicals used on citrus. Economic thresholds and various cost-benefit analyses are discussed. A list of practical recommendations to growers was drawn up, and possibilities for future research are presented.
- Full Text:
- Date Issued: 2008
- Authors: Kirkman, Wayne
- Date: 2008
- Subjects: Cryptophlebia leucotreta , Cryptophlebia leucotreta -- Control , Pests -- Biological control , Citrus -- Diseases and pests
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5794 , http://hdl.handle.net/10962/d1005482 , Cryptophlebia leucotreta , Cryptophlebia leucotreta -- Control , Pests -- Biological control , Citrus -- Diseases and pests
- Description: False codling moth (FCM), Thaumatotibia (=Cryptophlebia) leucotreta (Meyr) (Lepidoptera: Tortricidae), is one of the most important pests on citrus. The Cryptophlebia leucotreta granulovirus (CrleGV) has been developed into a successful biological control agent, registered under the name Cryptogran, and is currently the preferred product for the control of FCM on citrus in South Africa. A prerequisite to the continued success of Cryptogran as a means of controlling false codling moth is to understand the factors affecting field persistence of the virus, and to find ways to improve it. The aim of this study was to gain a clearer understanding of the product and the abiotic and biotic factors affecting its persistence in the field, and to investigate methods to improve this persistence. The effect of UV-irradiation on the virus was determined, and various products were tested as UV protectants in laboratory bioassays. Lignin was the most effective additive, and was tested in several field trials, where it also enhanced the efficacy of Cryptogran. Laboratory trials indicated that Cryptogran is rainfast. Cryptogran applications early in the season had a longer period of residual activity than sprays applied closer to harvest. Daytime applications were less effective that evening sprays. Sprays applied coinciding with peaks in pheromone moth trap catches were more effective than those applied between peaks. Biotic factors influencing persistence were investigated. Residual efficacy was longer when treatments were applied to blocks than as single tree treatments. Attempts were made to quantify the effect of the navel end of a navel orange on the field persistence of Cryptogran. Cryptogran was shown to be compatible with many agricultural chemicals used on citrus. Economic thresholds and various cost-benefit analyses are discussed. A list of practical recommendations to growers was drawn up, and possibilities for future research are presented.
- Full Text:
- Date Issued: 2008
Identifying volatile emissions associated with False Codling Moth infested citrus fruit
- Authors: Van der Walt, Rachel
- Date: 2012
- Subjects: Citrus -- Diseases and pests , Insect pests , Cryptophlebia leucotreta
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10343 , http://hdl.handle.net/10948/d1020056
- Description: False codling moth is a known pest of economic importance to many cultivated crops in South Africa and Africa south of the Sahara, and is particularly severe on citrus. If the fruit is infested just before harvest the chances of detecting signs of infestation are very low. As a result, the risk of packaging infested fruit and exporting them as healthy fruit is high. It is therefore a priority to develop a post-harvest technique for detection of False codling moth in citrus fruit at different levels of infestation in order to reduce phytosanitary risk. Compounds released and detected were indicative of infestation and were not insect produced but naturally produced fruit volatiles emitted at higher levels as a result of the insect within the fruit. Five major volatile compounds of interest were released by the infested oranges. These major volatile compounds include D-limonene, 3,7-dimethyl-1,3,6-octatriene, (E)-4,8-dimethyl-1,3,7-nonatriene, caryophyllene and naphthalene. Limonene was one of the most abundant volatile compounds released by the infested citrus fruit. Naphthalene, which is possibly produced due to larval feeding and development within the fruit maintained higher concentrations than controls throughout the infestation within the fruit. Naphthalene would be a good indicator of False codling moth infestation, however, not primarily for early infestation detection. A significantly higher concentration of D-limonene, 3,7-dimethyl-1,3,6-octatriene, (E)-4,8-dimethyl-1,3,7-nonatriene and naphthalene was detected using the SEP over the SPME technique. The application of an SPME procedure and the utilization of this method for detection of volatiles present in the headspace of intact infested fruit are evaluated and the possible volatile compounds diagnostic of Thaumatotibia leucotreta infestation of orange fruit and differences in volatile compound response in different orange varieties is discussed.
- Full Text:
- Date Issued: 2012
- Authors: Van der Walt, Rachel
- Date: 2012
- Subjects: Citrus -- Diseases and pests , Insect pests , Cryptophlebia leucotreta
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10343 , http://hdl.handle.net/10948/d1020056
- Description: False codling moth is a known pest of economic importance to many cultivated crops in South Africa and Africa south of the Sahara, and is particularly severe on citrus. If the fruit is infested just before harvest the chances of detecting signs of infestation are very low. As a result, the risk of packaging infested fruit and exporting them as healthy fruit is high. It is therefore a priority to develop a post-harvest technique for detection of False codling moth in citrus fruit at different levels of infestation in order to reduce phytosanitary risk. Compounds released and detected were indicative of infestation and were not insect produced but naturally produced fruit volatiles emitted at higher levels as a result of the insect within the fruit. Five major volatile compounds of interest were released by the infested oranges. These major volatile compounds include D-limonene, 3,7-dimethyl-1,3,6-octatriene, (E)-4,8-dimethyl-1,3,7-nonatriene, caryophyllene and naphthalene. Limonene was one of the most abundant volatile compounds released by the infested citrus fruit. Naphthalene, which is possibly produced due to larval feeding and development within the fruit maintained higher concentrations than controls throughout the infestation within the fruit. Naphthalene would be a good indicator of False codling moth infestation, however, not primarily for early infestation detection. A significantly higher concentration of D-limonene, 3,7-dimethyl-1,3,6-octatriene, (E)-4,8-dimethyl-1,3,7-nonatriene and naphthalene was detected using the SEP over the SPME technique. The application of an SPME procedure and the utilization of this method for detection of volatiles present in the headspace of intact infested fruit are evaluated and the possible volatile compounds diagnostic of Thaumatotibia leucotreta infestation of orange fruit and differences in volatile compound response in different orange varieties is discussed.
- Full Text:
- Date Issued: 2012
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