Host specificity tests on leaf-feeding insects aberrations from the use of excised leaves
- Olckers, T, Hulley, Patrick E
- Authors: Olckers, T , Hulley, Patrick E
- Date: 1994
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/452340 , vital:75121 , https://journals.co.za/doi/pdf/10.10520/AJA10213589_137
- Description: Starvation tests, in which herbivorous insects are confined to plants under cage conditions, are integral to determining the host range and suitability of candidate agents for weed biocontrol (Cullen 1990). The acceptance or rejection of test plants under these artificial conditions can, however, be influenced by the quality of the plants presented (Shepherd 1990); starvation tests on leaf-feeding insects are often carried out with bouquets or excised leaves as opposed to whole plants. This study presents the results of two independent experiments that illustrate potential problems associated with the use of excised leaves during host specificity tests.
- Full Text:
- Date Issued: 1994
- Authors: Olckers, T , Hulley, Patrick E
- Date: 1994
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/452340 , vital:75121 , https://journals.co.za/doi/pdf/10.10520/AJA10213589_137
- Description: Starvation tests, in which herbivorous insects are confined to plants under cage conditions, are integral to determining the host range and suitability of candidate agents for weed biocontrol (Cullen 1990). The acceptance or rejection of test plants under these artificial conditions can, however, be influenced by the quality of the plants presented (Shepherd 1990); starvation tests on leaf-feeding insects are often carried out with bouquets or excised leaves as opposed to whole plants. This study presents the results of two independent experiments that illustrate potential problems associated with the use of excised leaves during host specificity tests.
- Full Text:
- Date Issued: 1994
Resolving ambiguous results of host-specificity tests the case of two Leptinotarsa species (Coleoptera: Chrysomelidae) for biological control of Solanum elaeagnifolium Cavanilles (Solanaceae) in South Africa
- Olckers, T, Hulley, Patrick E
- Authors: Olckers, T , Hulley, Patrick E
- Date: 1994
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/452358 , vital:75122 , https://hdl.handle.net/10520/AJA10213589_421
- Description: Two leaf-feeding chrysomelids from North America, Leptinotarsa texana (Schaeffer) and Leptinotarsa defecta (Stal), are promising candidates for the biological control of Solanum elaeagnifolium Cavanilles (Solanaceae) in South Africa. Permission for release was delayed because the beetles fed on cultivated eggplant (Solanum melongena Linnaeus) under cage conditions. After considerable deliberation and further investigation, it was concluded that the results of the cage tests had been overemphasized. The beetles were cleared for release in South Africa on the following grounds: (i) neither Leptinotarsa species attacks eggplant in their native North American habitats; (ii) in South Africa, many insect herbivores of Solanaceae feed on eggplant in cultivation but cause minor damage relative to cosmopolitan polyphagous pests; (iii) as with L. texana and L. defecta, Conchyloctenia tigrina Olivier, a South African chrysomelid that also occurs on eggplant in cultivation, fed on eggplant in indoor cages, but preferred its natural Solanum hosts in large outdoor cages; (iv) eggplant cultivation methods include crop rotation and severe pesticide regimes, which should exclude Leptinotarsa along with the other insects.
- Full Text:
- Date Issued: 1994
- Authors: Olckers, T , Hulley, Patrick E
- Date: 1994
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/452358 , vital:75122 , https://hdl.handle.net/10520/AJA10213589_421
- Description: Two leaf-feeding chrysomelids from North America, Leptinotarsa texana (Schaeffer) and Leptinotarsa defecta (Stal), are promising candidates for the biological control of Solanum elaeagnifolium Cavanilles (Solanaceae) in South Africa. Permission for release was delayed because the beetles fed on cultivated eggplant (Solanum melongena Linnaeus) under cage conditions. After considerable deliberation and further investigation, it was concluded that the results of the cage tests had been overemphasized. The beetles were cleared for release in South Africa on the following grounds: (i) neither Leptinotarsa species attacks eggplant in their native North American habitats; (ii) in South Africa, many insect herbivores of Solanaceae feed on eggplant in cultivation but cause minor damage relative to cosmopolitan polyphagous pests; (iii) as with L. texana and L. defecta, Conchyloctenia tigrina Olivier, a South African chrysomelid that also occurs on eggplant in cultivation, fed on eggplant in indoor cages, but preferred its natural Solanum hosts in large outdoor cages; (iv) eggplant cultivation methods include crop rotation and severe pesticide regimes, which should exclude Leptinotarsa along with the other insects.
- Full Text:
- Date Issued: 1994
Sunbird Movements: a Review, with Posslble Models
- Craig, Adrian J F K, Hulley, Patrick E
- Authors: Craig, Adrian J F K , Hulley, Patrick E
- Date: 1994
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/447856 , vital:74679 , https://doi.org/10.1080/00306525.1994.9639672
- Description: Based on current fieldwork, we propose four possible models to explain the winter influx of sunbirds which we have observed: the birds may be (1) “winter residents”, which move annually to a wintering area and remain there; (2) “shoppers”, which periodically investigate feeding areas within their home range and feed opportunistically where nectar is most abundant; (3) “tourists”, which successively visit a series of sites on a regular itinerary; (4) “nomads”, which move unpredictably to new areas whenever food supplies decline. and have no home base. Current data on sunbird movements are reviewed, and in a few cases the winter resident model is unlikely, but generally it is not yet possible to eliminate any of the hypotheses. Moult cycles based on both field and museum studies may provide additional information, as movements are unlikely while active wing-moult is in progress; some species show interrupted wing-moult, which may be associated with long-distance flights.
- Full Text:
- Date Issued: 1994
- Authors: Craig, Adrian J F K , Hulley, Patrick E
- Date: 1994
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/447856 , vital:74679 , https://doi.org/10.1080/00306525.1994.9639672
- Description: Based on current fieldwork, we propose four possible models to explain the winter influx of sunbirds which we have observed: the birds may be (1) “winter residents”, which move annually to a wintering area and remain there; (2) “shoppers”, which periodically investigate feeding areas within their home range and feed opportunistically where nectar is most abundant; (3) “tourists”, which successively visit a series of sites on a regular itinerary; (4) “nomads”, which move unpredictably to new areas whenever food supplies decline. and have no home base. Current data on sunbird movements are reviewed, and in a few cases the winter resident model is unlikely, but generally it is not yet possible to eliminate any of the hypotheses. Moult cycles based on both field and museum studies may provide additional information, as movements are unlikely while active wing-moult is in progress; some species show interrupted wing-moult, which may be associated with long-distance flights.
- Full Text:
- Date Issued: 1994
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