PEST RISK ANALYSIS (PRA) TRAINING Group Exercises Manual

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APPENDIX 8 PEST RISK ANALYSIS TRAINING - GROUP EXERCISES MANUAL Grove et al.: Thrips species associated with mango trees in South Africa 155 Table 1. Species of thrips collected on mango flowers, leaves and fruit at several localities in South Africa. Species Localities Flowers Suborder Tubulifera Haplothrips bedfordi Jacot-Guillarmod (Phlaeothripidae) Haplothrips clarisetis Priesner (Phlaeothripidae) Haplothrips gowdeyi (Franklin) (Phlaeothripidae) Suborder Terebrantia Florithrips dilutus (Hood) (Thripidae) Frankliniella occidentalis (Pergande) (Thripidae) Frankliniella schultzei (Trybom) (Thripidae) Hydatothrips adolfifriderici (Karny) (Thripidae) Megalurothrips sjostedti (Trybom) (Thripidae) Ramaswamiahiella subnudula Karny (Thripidae) Scirtothrips aurantii Faure (Thripidae) Taeniothrips gowdeyi (Bagnall) (Thripidae) Thrips acaciae Trybom (Thripidae) Thrips tenellus Trybom (Thripidae) Leaves Friedenheim, Kaapmuiden, Nelspruit, Nondweni Friedenheim, Kaapmuiden, Letsitele, Nelspruit, Malelane Friedenheim, Hoedspruit, Kaapmuiden, Nelspruit Letsitele Letsitele Friedenheim, Kaapmuiden, Letsitele, Nelspruit, Nelspruit Friedenheim, Hoedspruit, Kaapmuiden, Nelspruit Hoedspruit, Letsitele, Nelspruit Friedenheim, Hoedspruit, Kaapmuiden, Letsitele, Malelane, Nelspruit, Nondweni Kaapmuiden, Hoedspruit, Letsitele Friedenheim, Nelspruit Friedenheim, Hoedspruit, Kaapmuiden, Letsitele, Malelane, Nelspruit, Nondweni Suborder Tubulifera Aleurodothrips fasciapennis Franklin (Phlaeothripidae) Friedenheim, Nelspruit Haplothrips bedfordi Jacot-Guillarmod (Phlaeothripidae) Friedenheim, Kaapmuiden, Letsitele, Nelspruit Haplothrips clarisetis Priesner (Phlaeothripidae) LetsiteIe Suborder Terebrantia Scirtothrips aurantii Faure (Thripidae) Friedenheim, Hoedspruit, Kaapmuiden, Letsitele, Malelane, Nelspruit Selenothrips rubocinctus (Giard) (Thripidae) Nondweni, Friedenheim, Nelspruit Fruit Suborder Tubulifera Haplothrips bedfordi Jacot-Guillarmod (Phlaeothripidae) Friedenheim, Nelspruit Suborder Terebrantia Scirtothrips aurantii Faure (Thripidae) Friedenheim, Hoedspruit, Kaapmuiden, Letsitele, Malelane, Nelspruit Selenothrips rubocinctus (Giard) (Thripidae) Friedenheim, Nondweni, Hoedspruit, Nelspruit enable the continued monitoring of emerging adults. Glass plates were removed weekly and replaced with new ones. The removed plates were covered with clear polyethylene plastic wrap and taken to the laboratory for evaluation. As it is difficult to distinguish between the larvae of the different species, only the adults were counted on both sides of the glass plate. RESULTS AND DISCUSSION Thrips survey Thirteen species were identified from the flowers, five from the leaves and three from the fruit (Table 1). Haplothrips bedfordi Jacot-Guillarmod, a predatory thrips, occurred on flowers, leaves and fruit and was collected at five sites (Table 1). Haplothrips bedfordi was found in association with S. aurantii on the fruit. This species is a predator of S. aurantii on citrus, where both larvae and adults feed on S. aurantii (Bedford 1943). Haplothrips clarisetis Priesner occurred on the flowers and leaves (Table 1). Haplothrips gowdeyi (Franklin) was collected from the flowers at four localities (Table 1). Haplothrips clarisetis and H. gowdeyi are known plant feeders and appear on a wide range of host plants (Zur Strassen 1960; Gilbert 1990). Florithrips dilutus (Hood) was only collected from the flowers at one locality (Table 1). 82
PEST RISK ANALYSIS TRAINING - GROUP EXERCISES MANUAL APPENDIX 8 156 African Entomology Vol. 9, No. 2, 2001 Frankliniella occidentalis was collected for the first time on mango flowers in this study (Table 1). Although found at Letsitele, this species may expand its range as it was introduced during the 1980s (Giliomee 1989). This species is highly polyphagous, having been recorded on numerous hosts (Brodsgaard 1989; Mound 1997). In Israel, where serious damage is inflicted on mango fruit, very large numbers of F. occidentalis were present on the inflorescences (Ben-Dov et al. 1992; Wysoki et al. 1993). Such numbers have never been observed in South Africa and it remains to be seen whether or not this species can inflict the levels of damage observed in Israel. Frankliniella schultzei (Trybom), known as the common flower thrips, occurred at four localities (Table 1). This polyphagous and flower-living species has a worldwide distribution and can damage young leaves within the bud (Mound 1997). It is known to carry spores of mildews, moulds and rusts from infected plants and is also a vector of tomato spotted wilt virus (Ullman et al. 1997). Frankliniella schultzei also occurs in citrus flowers in South Africa but does not cause damage (M.J. Gilbert, pers. comm.). Hydatothrips adolfifriderici (Karny) was only collected on one occasion (Table 1). It is known to occur on a wide range of host plants, including legumes (Zur Strassen 1960; Mound 1997). Megalurothrips sjostedti (Trybom) was collected from mango flowers at four localities (Table 1). This species is known as the bean thrips in Africa and is a major pest of cowpeas, where mechanical damage to flowers may result in yield loss (Alghali 1992). Ramaswamiahiella subnudula Karny was collected from flowers at three localities (Table 1). Scirtothrips aurantii was collected from the flowers, leaves and fruit and occurred at all collecting sites (Table 1). This species was only collected from new leaves and young fruit and it seemed that feeding did not take place on mature leaves and fruit. Both adults and larvae were observed to cause lesions on the fruit, leaf malformation and stunting of new growth. The lesions on the fruit consisted of silvering and cracking of the skin. The damage on the fruit was only cosmetic and no harm was done to the fruit flesh. Mango fruit with large lesions are not suitable for export. According to the export standards of the South African Mango Growers’ Association, lesions larger than 400 mm 2 for count 7-14 and 500 mm 2 for count 4-6 fruit are not acceptable for export. Criteria for the local market are not as strict, but appearance of the fruit affects its marketability. This species appeared to be the most economically important thrips species on mango and is also a well documented pest on citrus in South Africa (Gilbert & Bedford 1998). Selenothrips rubrocinctus fed on both young and mature leaves and fruit but was not found in the flowers (Table 1). Characteristically associated with feeding damage on the fruit and leaves were numerous small, shiny black spots of excreta. Selenothrips rubrocinctus fed on both sides of the leaves and caused rust-coloured feeding scars as well as curled leaf edges. Greyish lesions were caused on the mango fruit. Although S. rubrocinctus can become a severe pest in young mango plantings (Hill 1975), numbers in the orchards were usually low and seemed to be under good biological control. The phytoseiid mites, Euseius sp. nr. rhusi, Iphiseius degenerans (Berlese), Typhlodromus vescus Van der Merwe and Euseius citri (Van der Merwe & Ryke) were found in association with S. rubrocinctus and seemed to regulate thrips numbers. Taeniothrips gowdeyi (Bagnall) was found in inflorescences at three sites (Table 1). It occurs commonly within citrus flowers but its numbers are low compared to Thrips tenellus Trybom (Gilbert 1990). Thrips acaciae Trybom was collected from flowers at two localities (Table 1) and is also known to occur in the flowers of Acacia karroo (Zur Strassen 1960). Thrips tenellus was common in the mango flowers and occurred at all the collecting sites (Table 1). It is also commonly found in citrus flowers and in the flowers of Acacia spp. (Gilbert 1990). Both T. acaciae and T. tenellus probably feed on pollen. Very high numbers of Thrips spp. were observed in the flowers, but fruit abortion and yield loss did not seem to be affected. Aleurodothrips fasciapennis (Franklin), which was collected from the leaves at two localities (Table 1), is a predatory thrips that feeds on scale insects (Palmer & Mound 1989). This species is known to prey on the mango scale Aulacaspis tubercularis Newstead in South Africa (Labuschagne 1993). Apart from thrips, there was a large complex of other insects and mites present in the flowers. The most noteworthy of these were Orius spp. (Anthocoridae), which were commonly found preying on thrips in the flowers. Many species of thrips are known to transmit fungi on their bodies by contact and movement. 83
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Table of Contents Acknowledgements.
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FOREWORD Welcome to the IPPC introd
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GROUP EXERCISE NO. 1 PEST RISK ANAL
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PEST RISK ANALYSIS (PRA) TRAINING Group Exercises Manual

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