Pub Date : 2023-06-27DOI: 10.17159/2254-8854/2023/a14183
Tapiwa Mushore, C. Coombes, M. Hill
The southern and eastern parts of the African Fynbos region favour the production of honeybush tea. Honeybush biomass and extracts are used to prepare a beverage both locally and internationally, mainly as herbal tea with health benefits. Honeybush tea is mostly grown organically requiring natural control measures for pests and diseases. The leafhopper, Molopopterus sp., is one of the most important pests of cultivated honeybush in South Africa, as its feeding compromises the quality and quantity of the yield through leaf discolouration and reduction of the photosynthetic area. Local entomopathogenic fungi (EPF) can provide a pool of potential biocontrol agents for this pest. Therefore, a total of 98 soil samples were collected from organically grown honeybush fields and vegetation surrounding the honeybush fields in the Western Cape province of South Africa. Entomopathogenic fungi were isolated using the insect bait method and were characterised using molecular techniques. Twenty fungal isolates of Metarhizium anisopliae and Fusarium oxysporum were recovered from soil samples, of which 70% were from honeybush fields and 30% were from surrounding vegetation. Fusarium oxysporum isolates comprised 20% of the recovered isolates; M. anisopliae the remainder. Laboratory bioassays of the recovered isolates against adults and nymphs of the leafhopper, showed that F. oxysporum isolates caused 10–45% mortality and M. anisopliae isolates 30–80% mortality. Metarhizium anisopliae isolates J S1, KF S3, KF S11, KF S13, LS1 and LS2 were the most virulent and induced over 60% mortality in both nymphs and adults at a concentration of 1 × 107 conidia/ml.
{"title":"Entomopathogenic fungi associated with cultivated honeybush, Cyclopia spp., in South Africa and their pathogenicity towards a leafhopper pest, Molopopterus sp. (Hemiptera: Cicadellidae)","authors":"Tapiwa Mushore, C. Coombes, M. Hill","doi":"10.17159/2254-8854/2023/a14183","DOIUrl":"https://doi.org/10.17159/2254-8854/2023/a14183","url":null,"abstract":"The southern and eastern parts of the African Fynbos region favour the production of honeybush tea. Honeybush biomass and extracts are used to prepare a beverage both locally and internationally, mainly as herbal tea with health benefits. Honeybush tea is mostly grown organically requiring natural control measures for pests and diseases. The leafhopper, Molopopterus sp., is one of the most important pests of cultivated honeybush in South Africa, as its feeding compromises the quality and quantity of the yield through leaf discolouration and reduction of the photosynthetic area. Local entomopathogenic fungi (EPF) can provide a pool of potential biocontrol agents for this pest. Therefore, a total of 98 soil samples were collected from organically grown honeybush fields and vegetation surrounding the honeybush fields in the Western Cape province of South Africa. Entomopathogenic fungi were isolated using the insect bait method and were characterised using molecular techniques. Twenty fungal isolates of Metarhizium anisopliae and Fusarium oxysporum were recovered from soil samples, of which 70% were from honeybush fields and 30% were from surrounding vegetation. Fusarium oxysporum isolates comprised 20% of the recovered isolates; M. anisopliae the remainder. Laboratory bioassays of the recovered isolates against adults and nymphs of the leafhopper, showed that F. oxysporum isolates caused 10–45% mortality and M. anisopliae isolates 30–80% mortality. Metarhizium anisopliae isolates J S1, KF S3, KF S11, KF S13, LS1 and LS2 were the most virulent and induced over 60% mortality in both nymphs and adults at a concentration of 1 × 107 conidia/ml. ","PeriodicalId":7566,"journal":{"name":"African Entomology","volume":" ","pages":""},"PeriodicalIF":0.8,"publicationDate":"2023-06-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42113543","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-05-18DOI: 10.17159/2254-8854/2023/a10672
T. Mugala, D. Visser, A. Malan, P. Addison
The leaf miner, Liriomyza huidobrensis (Diptera: Agromyzidae) is a polyphagous fly, which infests a wide range of vegetables and ornamental plants. However, scant knowledge exists of the biology and ecology of the pest in the Western Cape province of South Africa, both of which are essential components in developing an effective management programme. Several aspects of its biology and ecology were studied in two potato [Solanum tuberosum L. (Solanales: Solanaceae)] fields in the Sandveld region during both winter and summer months. The population densities of adult L. huidobrensis were monitored using yellow sticky traps, which were retrieved and counted once every two weeks (June 2019 to January 2020). The number of leaf miner adults caught throughout the summer and winter monitoring periods was significantly different. In addition, 50 randomly selected plants were assessed for leaf damage (in the form of punctures and mines) using presence/absence sampling. Leaf miner persistence within the soil was confirmed through one-time soil sampling of the two fields, one month after harvesting. Leaf miner pupae were detected in the soil samples after the potatoes were harvested. However, no adult emergence was recorded among the collected pupae under laboratory conditions. The observed trend was that the traps, in both fields, caught an increasing number of leaf miners as the crops matured. Damage occurred in both the monitored fields as early as week four, after plant emergence. Of the five parasitoid species collected, Diglyphus isaea (Hymenoptera: Eulophidae) was the most abundant.
{"title":"Occurrence of the potato leaf miner, Liriomyza huidobrensis (Diptera: Agromyzidae), and parasitoids in potato fields and natural vegetation of the Western Cape province, South Africa","authors":"T. Mugala, D. Visser, A. Malan, P. Addison","doi":"10.17159/2254-8854/2023/a10672","DOIUrl":"https://doi.org/10.17159/2254-8854/2023/a10672","url":null,"abstract":"The leaf miner, Liriomyza huidobrensis (Diptera: Agromyzidae) is a polyphagous fly, which infests a wide range of vegetables and ornamental plants. However, scant knowledge exists of the biology and ecology of the pest in the Western Cape province of South Africa, both of which are essential components in developing an effective management programme. Several aspects of its biology and ecology were studied in two potato [Solanum tuberosum L. (Solanales: Solanaceae)] fields in the Sandveld region during both winter and summer months. The population densities of adult L. huidobrensis were monitored using yellow sticky traps, which were retrieved and counted once every two weeks (June 2019 to January 2020). The number of leaf miner adults caught throughout the summer and winter monitoring periods was significantly different. In addition, 50 randomly selected plants were assessed for leaf damage (in the form of punctures and mines) using presence/absence sampling. Leaf miner persistence within the soil was confirmed through one-time soil sampling of the two fields, one month after harvesting. Leaf miner pupae were detected in the soil samples after the potatoes were harvested. However, no adult emergence was recorded among the collected pupae under laboratory conditions. The observed trend was that the traps, in both fields, caught an increasing number of leaf miners as the crops matured. Damage occurred in both the monitored fields as early as week four, after plant emergence. Of the five parasitoid species collected, Diglyphus isaea (Hymenoptera: Eulophidae) was the most abundant. ","PeriodicalId":7566,"journal":{"name":"African Entomology","volume":" ","pages":""},"PeriodicalIF":0.8,"publicationDate":"2023-05-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43396763","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-05-18DOI: 10.17159/2254-8854/2023/a14027
Aletta J Van Tonder, G. P. Nortjé, B. Botha
Pheromone-based or semiochemical lures for insect detection and monitoring in agriculture is common practice. Many countries exempt these devices from regulatory requirements, but not South Africa. The question arises whether the pheromone/semiochemical lures influence the naturally occurring compounds significantly, to justify concern for human toxicity and ecotoxicity. T.V. PheroLure® is a novel five-component lure developed by Insect Science (Pty) Ltd. used for monitoring African bollworm, Helicoverpa armigera (an important insect pest on tomatoes). T.V. PheroLure® is a volatile organic compound (VOC) blend impregnated in a polyethylene bulb. The influence of T.V. PheroLure® on the volatile profile of a tomato field was evaluated in a commercial growing area of South Africa. Tomato VOCs were collected before, during and after the application of six T.V. PheroLures® in yellow bucket funnel traps randomly distributed over 1 ha. VOCs were collected from planting until harvest (22 weeks) at five randomly selected sites. Collection also took place in adjacent tomato fields where no T.V. PheroLure® was applied. The constituents of T.V. PheroLure® had no significant influence on the naturally occurring VOCs observed in the tomato field. The results suggest that the concern for toxicity and ecotoxicity is unjustified when using semiochemical devices for monitoring purposes. The natural physiology of the plant, rather than T.V. PheroLure®, influenced the VOCs observed in a tomato field.
{"title":"T.V. PheroLure® : Volatile emission by semiochemical lures and the impact thereof on the volatile profile of a commercial tomato field","authors":"Aletta J Van Tonder, G. P. Nortjé, B. Botha","doi":"10.17159/2254-8854/2023/a14027","DOIUrl":"https://doi.org/10.17159/2254-8854/2023/a14027","url":null,"abstract":"Pheromone-based or semiochemical lures for insect detection and monitoring in agriculture is common practice. Many countries exempt these devices from regulatory requirements, but not South Africa. The question arises whether the pheromone/semiochemical lures influence the naturally occurring compounds significantly, to justify concern for human toxicity and ecotoxicity. T.V. PheroLure® is a novel five-component lure developed by Insect Science (Pty) Ltd. used for monitoring African bollworm, Helicoverpa armigera (an important insect pest on tomatoes). T.V. PheroLure® is a volatile organic compound (VOC) blend impregnated in a polyethylene bulb. The influence of T.V. PheroLure® on the volatile profile of a tomato field was evaluated in a commercial growing area of South Africa. Tomato VOCs were collected before, during and after the application of six T.V. PheroLures® in yellow bucket funnel traps randomly distributed over 1 ha. VOCs were collected from planting until harvest (22 weeks) at five randomly selected sites. Collection also took place in adjacent tomato fields where no T.V. PheroLure® was applied. The constituents of T.V. PheroLure® had no significant influence on the naturally occurring VOCs observed in the tomato field. The results suggest that the concern for toxicity and ecotoxicity is unjustified when using semiochemical devices for monitoring purposes. The natural physiology of the plant, rather than T.V. PheroLure®, influenced the VOCs observed in a tomato field.","PeriodicalId":7566,"journal":{"name":"African Entomology","volume":" ","pages":""},"PeriodicalIF":0.8,"publicationDate":"2023-05-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44717390","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-05-18DOI: 10.17159/2254-8854/2023/a14047
Vhuawelo Simba, Inam Yekwayo, T. Mwabvu
Expansion and intensification of agroecosystems is one of the major causes of habitat loss in the savanna biome in South Africa. As such, this study sought to determine the influence of commercial subtropical fruit plantations (banana and macadamia) on species richness, abundance, and composition of surface-active arthropods compared to the savanna biome. Given that pesticides and herbicides are applied from spring to early autumn in banana and macadamia plantations, we sampled in winter to reduce the potential impact of pesticides and herbicides. Surface-active arthropods were sampled using pitfall traps. Habitat type did not affect species richness and abundance of ants and spiders, as well as species richness of beetles. However, significantly greater abundance of beetles was recorded in the macadamia plantation compared to the banana and savanna. This could have been due to greater abundance of herbivorous beetles and other insects, which would have increased the diversity of predatory beetles. Furthermore, unlike the banana plantation, the macadamia plantation was characterised by a deep leaf litter layer and the presence of weeds and grasses, which probably increased abundance of beetles. Species composition indicated that the studied arthropod taxa associate with specific habitats, as demonstrated by the three habitats supporting different species composition. Despite savanna habitat not supporting high species richness or abundance of surface-active arthropods, we recorded the highest number of unique species of ants and spiders in the savanna rather than in the plantations. These results highlight the importance of natural landscapes in conservation of surface-active arthropods.
{"title":"Commercial banana and macadamia plantations in a savanna matrix support high levels of arthropod diversity","authors":"Vhuawelo Simba, Inam Yekwayo, T. Mwabvu","doi":"10.17159/2254-8854/2023/a14047","DOIUrl":"https://doi.org/10.17159/2254-8854/2023/a14047","url":null,"abstract":"Expansion and intensification of agroecosystems is one of the major causes of habitat loss in the savanna biome in South Africa. As such, this study sought to determine the influence of commercial subtropical fruit plantations (banana and macadamia) on species richness, abundance, and composition of surface-active arthropods compared to the savanna biome. Given that pesticides and herbicides are applied from spring to early autumn in banana and macadamia plantations, we sampled in winter to reduce the potential impact of pesticides and herbicides. Surface-active arthropods were sampled using pitfall traps. Habitat type did not affect species richness and abundance of ants and spiders, as well as species richness of beetles. However, significantly greater abundance of beetles was recorded in the macadamia plantation compared to the banana and savanna. This could have been due to greater abundance of herbivorous beetles and other insects, which would have increased the diversity of predatory beetles. Furthermore, unlike the banana plantation, the macadamia plantation was characterised by a deep leaf litter layer and the presence of weeds and grasses, which probably increased abundance of beetles. Species composition indicated that the studied arthropod taxa associate with specific habitats, as demonstrated by the three habitats supporting different species composition. Despite savanna habitat not supporting high species richness or abundance of surface-active arthropods, we recorded the highest number of unique species of ants and spiders in the savanna rather than in the plantations. These results highlight the importance of natural landscapes in conservation of surface-active arthropods.","PeriodicalId":7566,"journal":{"name":"African Entomology","volume":" ","pages":""},"PeriodicalIF":0.8,"publicationDate":"2023-05-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47809780","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-05-18DOI: 10.17159/2254-8854/2023/a14949
Megan K. Reid, M. Hill, J. Coetzee
Classical biological control aims to suppress alien invasive plant populations by introducing host-specific natural enemies from the native range. This relies on the assumption that invasive plant populations in the invaded range benefit from the release of natural enemies. Pre-release surveys in the invaded range are a useful way to determine if enemy release applies to a particular invasive alien plant, and to determine what other factors may contribute to the invasion. Similarly, pre-release surveys gather information that can be used to compare invaded sites before and after the release of biological control agents and may also identify whether natural enemies have been accidentally introduced into the country. Pre-release surveys were conducted in South Africa on the invasive Nymphaea mexicana Zuccarini (Nymphaeaceae) to gather such information about this species, for which a biological control programme is being developed. There was lower diversity and abundance of herbivores in the native range compared to South Africa, suggesting that N. mexicana does experience enemy release at most sites in South Africa. This support for the enemy release hypothesis justifies the investment in biological control for its management. However, a native weevil, Bagous longulus Gyllenhal (Coleoptera: Curculionidae), was found feeding and reproducing on N. mexicana at three sites, resulting in damage to the leaves and suggesting that a novel association has formed between these species. Bagous longulus may have potential to be distributed to sites of N. mexicana where it is not present, though further investigation is necessary to confirm if its host range is suitable for this to be a safe endeavour. With the exception of sites where B. longulus was present, leaf sizes were large and damage was low, and there is no evidence that any natural enemies have been accidentally introduced from the native range. Findings such as these emphasise the importance of conducting thorough surveys during the development of biological control programmes.
{"title":"Love at first bite? Pre-release surveys reveal a novel association between a native weevil and the invasive Nymphaea mexicana Zuccarini (Nymphaeaceae) in South Africa","authors":"Megan K. Reid, M. Hill, J. Coetzee","doi":"10.17159/2254-8854/2023/a14949","DOIUrl":"https://doi.org/10.17159/2254-8854/2023/a14949","url":null,"abstract":"Classical biological control aims to suppress alien invasive plant populations by introducing host-specific natural enemies from the native range. This relies on the assumption that invasive plant populations in the invaded range benefit from the release of natural enemies. Pre-release surveys in the invaded range are a useful way to determine if enemy release applies to a particular invasive alien plant, and to determine what other factors may contribute to the invasion. Similarly, pre-release surveys gather information that can be used to compare invaded sites before and after the release of biological control agents and may also identify whether natural enemies have been accidentally introduced into the country. Pre-release surveys were conducted in South Africa on the invasive Nymphaea mexicana Zuccarini (Nymphaeaceae) to gather such information about this species, for which a biological control programme is being developed. There was lower diversity and abundance of herbivores in the native range compared to South Africa, suggesting that N. mexicana does experience enemy release at most sites in South Africa. This support for the enemy release hypothesis justifies the investment in biological control for its management. However, a native weevil, Bagous longulus Gyllenhal (Coleoptera: Curculionidae), was found feeding and reproducing on N. mexicana at three sites, resulting in damage to the leaves and suggesting that a novel association has formed between these species. Bagous longulus may have potential to be distributed to sites of N. mexicana where it is not present, though further investigation is necessary to confirm if its host range is suitable for this to be a safe endeavour. With the exception of sites where B. longulus was present, leaf sizes were large and damage was low, and there is no evidence that any natural enemies have been accidentally introduced from the native range. Findings such as these emphasise the importance of conducting thorough surveys during the development of biological control programmes. ","PeriodicalId":7566,"journal":{"name":"African Entomology","volume":" ","pages":""},"PeriodicalIF":0.8,"publicationDate":"2023-05-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41996414","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-05-10DOI: 10.17159/2254-8854/2023/a12593
T. K. Philips, Christie A Sukhdeo, S. Peck
A study on dung beetles attracted to carrion using baited pitfalls was conducted in eight Upper Guinean wet and moist forest sites as well as one savannah site in Ghana, West Africa. A total of 42 species and 1380 individuals were collected from all sites. The highest diversity was found in the Shai Hills savannah with 19 species while the lowest total of only four species was collected in the Cape Three Points forest. The forest sites combined had seven unique species while the savannah locality had 12 unique taxa. Most carrion feeders belong to the genus Onthophagus; Onthophagus liberianus made up 23% of the total catch and together with the next nine most abundant species accounted for 78% of the specimens collected. Two dung beetle tribes of African savannah species not noted as carrion feeders were strongly attracted to vertebrate carrion and included a member of the Oniticellini, Latodrepanus caelatus (Gerst.) and the Onitini, Onitis cupreus Castelnau. Additionally, a forest species of Sisyphini, Neosisyphus angulicollis Felsche, that is uncommon on carrion was attracted to carrion in large numbers. For two species, Onthophagus liberianus and O. rufopygus, studied herein and previously in the Ivory Coast, the relative attractiveness of carrion and dung in each country varied greatly, demonstrating behavioral plasticity in food choice.
在上几内亚的八个潮湿森林地区以及西非加纳的一个稀树草原地区，利用诱饵陷阱对被腐肉吸引的甲虫进行了研究。从所有地点共采集到42个物种和1380个个体。Shai Hills稀树草原的多样性最高，有19个物种，而Cape Three Points森林的物种总数最低，只有4个。森林地区总共有7个独特的物种，而稀树草原地区有12个独特的分类群。大多数食腐动物属于甲氧苄啶属；自由甲鱼占总捕获量的23%，加上接下来9个最丰富的物种，占采集标本的78%。非洲大草原物种的两个粪甲虫部落（不以腐肉为食）被脊椎动物的腐肉强烈吸引，其中包括一名奥尼蒂切里尼人，Latodrepanus caelatus（Gerst.）和奥尼蒂尼人，奥尼蒂斯·库佩乌斯·卡斯特尔诺。此外，一种在腐肉上不常见的西西弗森林物种，新西西弗，被大量腐肉吸引。对于本文和之前在象牙海岸研究的两个物种，即自由甲鱼（Onthophagus liberianus）和鲁弗皮格斯（O.rufopygus），腐肉和粪便在每个国家的相对吸引力差异很大，这表明了食物选择的行为可塑性。
{"title":"Dung beetles (Scarabaeidae: Scarabaeinae) attracted to carrion in Ghana, West Africa and evidence for adult food source plasticity","authors":"T. K. Philips, Christie A Sukhdeo, S. Peck","doi":"10.17159/2254-8854/2023/a12593","DOIUrl":"https://doi.org/10.17159/2254-8854/2023/a12593","url":null,"abstract":"A study on dung beetles attracted to carrion using baited pitfalls was conducted in eight Upper Guinean wet and moist forest sites as well as one savannah site in Ghana, West Africa. A total of 42 species and 1380 individuals were collected from all sites. The highest diversity was found in the Shai Hills savannah with 19 species while the lowest total of only four species was collected in the Cape Three Points forest. The forest sites combined had seven unique species while the savannah locality had 12 unique taxa. Most carrion feeders belong to the genus Onthophagus; Onthophagus liberianus made up 23% of the total catch and together with the next nine most abundant species accounted for 78% of the specimens collected. Two dung beetle tribes of African savannah species not noted as carrion feeders were strongly attracted to vertebrate carrion and included a member of the Oniticellini, Latodrepanus caelatus (Gerst.) and the Onitini, Onitis cupreus Castelnau. Additionally, a forest species of Sisyphini, Neosisyphus angulicollis Felsche, that is uncommon on carrion was attracted to carrion in large numbers. For two species, Onthophagus liberianus and O. rufopygus, studied herein and previously in the Ivory Coast, the relative attractiveness of carrion and dung in each country varied greatly, demonstrating behavioral plasticity in food choice.","PeriodicalId":7566,"journal":{"name":"African Entomology","volume":" ","pages":""},"PeriodicalIF":0.8,"publicationDate":"2023-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44069642","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-05-10DOI: 10.17159/2254-8854/2023/a13141
Sumarie Rossouw, L. L. Mathulwe, A. Malan, N. F. Stokwe
Entomopathogenic fungi (EPF) are effective and environment-friendly insect biological control agents. Ultraviolet (UV) light is known to have an effect on the survival of fungal conidia, and natural sunlight is potentially one of the most damaging factors undermining EPF persistence and pathogenicity. This study aimed to test the infection potential of an isolate of Beauveria bassiana and five Metarhizium species after exposure to different light treatments, on soil and leaf surfaces under laboratory and field conditions, using Thaumatotibia leucotreta (Lepidoptera: Tortricidae) as the test host. Conidia were exposed either to growth light alone, which emits the same visible light as the sun, but excluding UV light, or directly exposed to UV light for 12 h. The results indicated no negative effect on the infection potential of the conidia of most species tested. The conidia of the two Metarhizium pinghaense (5HEID and TH149) isolates showed the greatest tolerance to visible light and UV radiation exposure on both soil and leaf surfaces. Exposure of M. pinghaense isolates to visible light on soil surfaces showed pathogenicity of > 80% for both isolates, and of between 58% and 88% after exposure to UV light. On leaf surfaces, three Metarhizium isolates, M. pinghaense (5HEID and TH149) and M. majus (TH153) had > 90% pathogenicity following exposure to UV light, and M. pinghaense (TH149) and M. robertsii (6EIKEN) showed greater tolerance of > 70%, under laboratory conditions. However, the pathogenicity of the EPF isolates was very low in field trials, indicating that further trials on the use of formulations and adjuvants with the isolates are needed to improve long-term persistence and efficacy under field conditions.
{"title":"Effect of visible light and ultraviolet light on the pathogenicity of entomopathogenic fungi to false codling moth, Thaumatotibia leucotreta (Lepidoptera: Tortricidae) larvae","authors":"Sumarie Rossouw, L. L. Mathulwe, A. Malan, N. F. Stokwe","doi":"10.17159/2254-8854/2023/a13141","DOIUrl":"https://doi.org/10.17159/2254-8854/2023/a13141","url":null,"abstract":"Entomopathogenic fungi (EPF) are effective and environment-friendly insect biological control agents. Ultraviolet (UV) light is known to have an effect on the survival of fungal conidia, and natural sunlight is potentially one of the most damaging factors undermining EPF persistence and pathogenicity. This study aimed to test the infection potential of an isolate of Beauveria bassiana and five Metarhizium species after exposure to different light treatments, on soil and leaf surfaces under laboratory and field conditions, using Thaumatotibia leucotreta (Lepidoptera: Tortricidae) as the test host. Conidia were exposed either to growth light alone, which emits the same visible light as the sun, but excluding UV light, or directly exposed to UV light for 12 h. The results indicated no negative effect on the infection potential of the conidia of most species tested. The conidia of the two Metarhizium pinghaense (5HEID and TH149) isolates showed the greatest tolerance to visible light and UV radiation exposure on both soil and leaf surfaces. Exposure of M. pinghaense isolates to visible light on soil surfaces showed pathogenicity of > 80% for both isolates, and of between 58% and 88% after exposure to UV light. On leaf surfaces, three Metarhizium isolates, M. pinghaense (5HEID and TH149) and M. majus (TH153) had > 90% pathogenicity following exposure to UV light, and M. pinghaense (TH149) and M. robertsii (6EIKEN) showed greater tolerance of > 70%, under laboratory conditions. However, the pathogenicity of the EPF isolates was very low in field trials, indicating that further trials on the use of formulations and adjuvants with the isolates are needed to improve long-term persistence and efficacy under field conditions.","PeriodicalId":7566,"journal":{"name":"African Entomology","volume":" ","pages":""},"PeriodicalIF":0.8,"publicationDate":"2023-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45501878","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-05-10DOI: 10.17159/2254-8854/2023/a10656
Alexander Csn Jeanrenraud, B. D. Letinić, Jean Mollett, B. Brooke, S. Oliver
Culex quinquefasciatus Say, 1823 and Anopheles arabiensis Patton, 1905 (Diptera: Culicidae) are often found breeding in the same water sources and engage in interspecific competition. Although Cx. quinquefasciatus is known to proliferate in a range of polluted environments, the ability of An. arabiensis to proliferate in polluted water has only been reported relatively recently. The effects of pollution and insecticide resistance on this competitive interaction are unknown. This study examined the effect of pollution on the dynamics of the interspecific competition. Three laboratory strains were used in this study: an insecticide susceptible and an insecticide resistant An. arabiensis, and an insecticide resistant Cx. quinquefasciatus. Larval pollutant tolerances of each strain were assessed and compared by determining the lethal concentration at 50% mortality (LC50). The larvae from each strain were exposed to either inorganic fertiliser or copper nitrate, following which eclosion success was assessed. The results showed that the insecticide resistant strains had higher emergence rates when reared in polluted conditions without competition, with the Cx. quinquefasciatus strain showing the highest rate of eclosion. This species also had a higher tolerance for metal pollution than the An. arabiensis strains. The effects of pollutants on oviposition choice were examined. Pollution altered adult oviposition choice. The effect of larval metal exposure had variable effects on the activity of metabolic detoxification enzymes. An insecticide resistant phenotype had greater tolerance to pollutants and possibly developmental advantages based on a variable detoxification response to the pollutant. Pollution can therefore alter interspecific competition dynamics between the malaria vector An. arabiensis and Cx. quinquefasciatus.
{"title":"The effect of pollution on the competitive dynamics of Anopheles arabiensis Patton, 1905 and Culex quinquefasciatus Say, 1823 (Diptera: Culicidae)","authors":"Alexander Csn Jeanrenraud, B. D. Letinić, Jean Mollett, B. Brooke, S. Oliver","doi":"10.17159/2254-8854/2023/a10656","DOIUrl":"https://doi.org/10.17159/2254-8854/2023/a10656","url":null,"abstract":"Culex quinquefasciatus Say, 1823 and Anopheles arabiensis Patton, 1905 (Diptera: Culicidae) are often found breeding in the same water sources and engage in interspecific competition. Although Cx. quinquefasciatus is known to proliferate in a range of polluted environments, the ability of An. arabiensis to proliferate in polluted water has only been reported relatively recently. The effects of pollution and insecticide resistance on this competitive interaction are unknown. This study examined the effect of pollution on the dynamics of the interspecific competition. Three laboratory strains were used in this study: an insecticide susceptible and an insecticide resistant An. arabiensis, and an insecticide resistant Cx. quinquefasciatus. Larval pollutant tolerances of each strain were assessed and compared by determining the lethal concentration at 50% mortality (LC50). The larvae from each strain were exposed to either inorganic fertiliser or copper nitrate, following which eclosion success was assessed. The results showed that the insecticide resistant strains had higher emergence rates when reared in polluted conditions without competition, with the Cx. quinquefasciatus strain showing the highest rate of eclosion. This species also had a higher tolerance for metal pollution than the An. arabiensis strains. The effects of pollutants on oviposition choice were examined. Pollution altered adult oviposition choice. The effect of larval metal exposure had variable effects on the activity of metabolic detoxification enzymes. An insecticide resistant phenotype had greater tolerance to pollutants and possibly developmental advantages based on a variable detoxification response to the pollutant. Pollution can therefore alter interspecific competition dynamics between the malaria vector An. arabiensis and Cx. quinquefasciatus. ","PeriodicalId":7566,"journal":{"name":"African Entomology","volume":" ","pages":""},"PeriodicalIF":0.8,"publicationDate":"2023-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45880273","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-03-23DOI: 10.17159/2254-8854/2023/a13406
Q. Guignard, J. Spaethe, B. Slippers, N. Nikolić, J. Allison
The woodwasp, Sirex noctilio, is a global pest of pines. Although it is known to be attracted to light and possess sexually dimorphic body colouration, the visual ecology of S. noctilio is poorly understood. Photoreceptor sensitivity of the compound eyes in S. noctilio is not sexually dimorphic. These previous results suggest that colour tracking of one sex by the other might not be an important input for mate searching. This study aimed to expand our knowledge of the visual system of S. noctilio by means of i) morphological description of the compound eyes and ocelli; and ii) semi-field behavioural tests of the colour preference of newly emerged wasps. Eye and ocellus morphological features were investigated in 21 males and 21 females. Measurement of male and female median ocellus diameter, compound eye surface area, number of ommatidia and facet diameter varied from 0.22 to 0.40 mm, 0.589 to 2.277 mm2, 1820 to 4207 and 1.88 × 10–2 to 2.82 × 10–2 mm, respectively. In addition, all traits significantly correlated with body size. Male and female wasps emerged from infested host material in a flight cage with five traps, each reflecting a different colour. Analysis of trap captures did not identify any colour preference, but an effect of trap location was observed with traps in the north-eastern position capturing more woodwasps, suggesting that other factors, e.g., global landmarks or other non-colour visual cues might guide initial flight behaviour of S. noctilio.
{"title":"Eye morphology and colour preferences in a semi-field test of the pine pest, Sirex noctilio (Hymenoptera: Siricidae)","authors":"Q. Guignard, J. Spaethe, B. Slippers, N. Nikolić, J. Allison","doi":"10.17159/2254-8854/2023/a13406","DOIUrl":"https://doi.org/10.17159/2254-8854/2023/a13406","url":null,"abstract":"The woodwasp, Sirex noctilio, is a global pest of pines. Although it is known to be attracted to light and possess sexually dimorphic body colouration, the visual ecology of S. noctilio is poorly understood. Photoreceptor sensitivity of the compound eyes in S. noctilio is not sexually dimorphic. These previous results suggest that colour tracking of one sex by the other might not be an important input for mate searching. This study aimed to expand our knowledge of the visual system of S. noctilio by means of i) morphological description of the compound eyes and ocelli; and ii) semi-field behavioural tests of the colour preference of newly emerged wasps. Eye and ocellus morphological features were investigated in 21 males and 21 females. Measurement of male and female median ocellus diameter, compound eye surface area, number of ommatidia and facet diameter varied from 0.22 to 0.40 mm, 0.589 to 2.277 mm2, 1820 to 4207 and 1.88 × 10–2 to 2.82 × 10–2 mm, respectively. In addition, all traits significantly correlated with body size. Male and female wasps emerged from infested host material in a flight cage with five traps, each reflecting a different colour. Analysis of trap captures did not identify any colour preference, but an effect of trap location was observed with traps in the north-eastern position capturing more woodwasps, suggesting that other factors, e.g., global landmarks or other non-colour visual cues might guide initial flight behaviour of S. noctilio.","PeriodicalId":7566,"journal":{"name":"African Entomology","volume":" ","pages":""},"PeriodicalIF":0.8,"publicationDate":"2023-03-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49071476","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-03-23DOI: 10.17159/2254-8854/2023/a13597
S. Nqayi, C. Zachariades, J. Coetzee, M. Hill, F. Chidawanyika, O. Uyi, A. McConnachie
Chromolaena odorata (L.) RM King and H Rob. (Asteraceae) has been subject to a biological control programme in South Africa for over three decades. A shoot-tip boring moth, Dichrorampha odorata Brown and Zachariades (Lepidoptera: Tortricidae), originating from Jamaica, was released as a biological control agent in 2013 but despite the release of substantial numbers of the insect, it has not established a permanent field population. Because climate incompatibility is a major constraint for classical biological control of invasive plants, and based on the differences in climate between Jamaica and South Africa and field observations at release sites, aspects of the thermal physiology of D. odorata were investigated to elucidate reasons for its failure to establish. Developmental time decreased with increasing temperatures ranging from 20 °C to 30 °C, with incomplete development for immature stages at 18 °C and 32 °C. The developmental threshold, t, was calculated as 8.45 °C with 872.4 degree-days required to complete development (K). A maximum of 6.5 generations per year was projected for D. odorata in South Africa, with the heavily infested eastern region of the country being the most eco-climatically suitable for establishment. The lower lethal temperature (LLT50) of larvae and adults was –4.5 and 1.8 °C, respectively. The upper lethal temperature (ULT50) for larvae was 39.6 °C whilst that of adults was 41.0 °C. Larvae thus had better cold tolerance compared to adults whereas adults had better heat tolerance compared to larvae. The critical thermal (CT) limits for adults were 3.4 ± 0.07 to 43.7 ± 0.12 °C. Acclimation at 20 °C for 7 days resulted in increased cold and heat tolerance with a CTmin and CTmax of 1.9 ± 0.06 and 44.4 ± 0.07 °C respectively, compared to the relative control, acclimated at 25 °C. Acclimation at 30 °C improved neither cold (CTmin: 5.9 ± 0.08 °C) nor heat tolerance (CTmax: 42.9 ± 0.10 °C). These results suggest that thermal requirements fall within field temperatures and are thus not the main constraining factor leading to poor establishment of D. odorata in South Africa.
{"title":"Do thermal requirements of Dichrorampha odorata, a shoot-boring moth for the biological control of Chromolaena odorata, explain its failure to establish in South Africa?","authors":"S. Nqayi, C. Zachariades, J. Coetzee, M. Hill, F. Chidawanyika, O. Uyi, A. McConnachie","doi":"10.17159/2254-8854/2023/a13597","DOIUrl":"https://doi.org/10.17159/2254-8854/2023/a13597","url":null,"abstract":"Chromolaena odorata (L.) RM King and H Rob. (Asteraceae) has been subject to a biological control programme in South Africa for over three decades. A shoot-tip boring moth, Dichrorampha odorata Brown and Zachariades (Lepidoptera: Tortricidae), originating from Jamaica, was released as a biological control agent in 2013 but despite the release of substantial numbers of the insect, it has not established a permanent field population. Because climate incompatibility is a major constraint for classical biological control of invasive plants, and based on the differences in climate between Jamaica and South Africa and field observations at release sites, aspects of the thermal physiology of D. odorata were investigated to elucidate reasons for its failure to establish. Developmental time decreased with increasing temperatures ranging from 20 °C to 30 °C, with incomplete development for immature stages at 18 °C and 32 °C. The developmental threshold, t, was calculated as 8.45 °C with 872.4 degree-days required to complete development (K). A maximum of 6.5 generations per year was projected for D. odorata in South Africa, with the heavily infested eastern region of the country being the most eco-climatically suitable for establishment. The lower lethal temperature (LLT50) of larvae and adults was –4.5 and 1.8 °C, respectively. The upper lethal temperature (ULT50) for larvae was 39.6 °C whilst that of adults was 41.0 °C. Larvae thus had better cold tolerance compared to adults whereas adults had better heat tolerance compared to larvae. The critical thermal (CT) limits for adults were 3.4 ± 0.07 to 43.7 ± 0.12 °C. Acclimation at 20 °C for 7 days resulted in increased cold and heat tolerance with a CTmin and CTmax of 1.9 ± 0.06 and 44.4 ± 0.07 °C respectively, compared to the relative control, acclimated at 25 °C. Acclimation at 30 °C improved neither cold (CTmin: 5.9 ± 0.08 °C) nor heat tolerance (CTmax: 42.9 ± 0.10 °C). These results suggest that thermal requirements fall within field temperatures and are thus not the main constraining factor leading to poor establishment of D. odorata in South Africa.","PeriodicalId":7566,"journal":{"name":"African Entomology","volume":" ","pages":""},"PeriodicalIF":0.8,"publicationDate":"2023-03-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49459037","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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