scholarly journals Seed survival of Australian Acacia in the Western Cape of South Africa in the presence of biological control agents and given environmental variation

PeerJ ◽  
2019 ◽  
Vol 7 ◽  
pp. e6816 ◽  
Author(s):  
Matthys Strydom ◽  
Ruan Veldtman ◽  
Mzabalazo Z. Ngwenya ◽  
Karen J. Esler
Keyword(s):  
South Africa ◽  
Biological Control ◽  
Seed Production ◽  
Western Cape ◽  
Biological Control Agents ◽  
Seed Survival ◽  
Quantitative Evidence ◽  
Before And After ◽  
Survival Proportion

Studies of invasive Australian Acacia have shown that many seeds are still produced and accumulate in soil stored seed banks regardless of the presence of seed-targeting biological control agents. This is despite claims of biological control success, although there is generally a lack of data on the seed production of invasive Australian Acacia before and after the release of the respective agents. We aimed to quantify seed production and seed survival of invasive Australian Acacia currently under biological control. The seed production and survival (proportion of aborted, predated and surviving seeds) of A. longifolia, A. pycnantha and A. saligna were each studied at four to five sites in the Western Cape of South Africa. The relationships between seed production and stand characteristics were determined and the relative effects of seed predation and abortion on seed survival were established. The investigated invasive Australian Acacia produced many seeds that survived the pre-dispersal stage despite long-term presence of released biological control agents. It was shown that seed crop size is the only significant factor influencing seed survival of the studied Australian Acacia species. Furthermore, the seeds surviving per tree and per square meter were related to tree size. No quantitative evidence was found to suggest that seed-reducing biological control agents are having an impact on the population dynamics of their Australian Acacia hosts. This study illustrates the importance of studying the seed ecology of invasive plants before biological control agents are selected and released.

Seasonal abundance and parasitism of Mesoclanis seed flies (Diptera: Tephritidae) in South Africa, and implications for the biological control of Chrysanthemoides monilifera (Asteraceae) in Australia

1998 ◽  
Vol 88 (4) ◽  
pp. 407-414 ◽  
Author(s):  
P.B. Edwards
Keyword(s):  
South Africa ◽  
Biological Control ◽  
Nature Reserve ◽  
Seasonal Abundance ◽  
Western Cape ◽  
Flowering Period ◽  
Eastern Cape ◽  
Biological Control Agents ◽  
Kwazulu Natal

AbstractThe seasonal abundance and rates of parasitism of three species of Mesoclanis seed flies was studied in South Africa. The three species occur on Chrysanthemoides monilifera, and were recorded during most months of the year, whenever C. monilifera was flowering. At three sites in KwaZulu-Natal, numbers of eggs per capitulum of Mesoclanis polana Munro were highest on C. monilifera rotundata between June and November (winter/spring), towards the end of the main flowering flush. Parasitism of M. polana was between 50% and 90% for most of the year. Two other species of Mesoclanis (M. magnipalpis Bezzi and M. dubia Walker) occurred together on C. m. rotundata in the Eastern Cape (St Francis Bay), where parasitism during the year was between 55% and 95%. Peak numbers of eggs per capitulum (M. magnipalpis and M. dubia combined) occurred in May/June (winter), in the latter part of the main flowering flush. Mesoclanis magnipalpis was the only species recorded on C. m. pisifera in De Hoop Nature Reserve (Western Cape), where there was only one peak of oviposition (May/June), coinciding with the short and discrete flowering period of this subspecies. Parasitism was between 50% and 65%. At least nine species of parasitoid were reared from immature Mesoclanis stages. Eurytoma sp. (Eurytomidae) was a dominant parasitoid at all sites. Results are discussed in relation to the possible effectiveness of species of Mesoclanis seed flies as biological control agents of C. monilifera in Australia.

Predatory mites from crops and pastures in South Africa:  potential natural enemies of redlegged earth mite Halotydeus destructor (Acari: Penthaleidae)

Zootaxa ◽  
2005 ◽  
Vol 1079 (1) ◽  
pp. 11 ◽  
Author(s):  
R. B. HALLIDAY
Keyword(s):  
South Africa ◽  
Biological Control ◽  
Natural Enemies ◽  
Predatory Mites ◽  
Generalist Predators ◽  
Western Cape ◽  
Biological Control Agents ◽  
Western Cape Province ◽  
Halotydeus Destructor ◽  
Redlegged Earth Mite

A survey was conducted in crops and pastures in the Western Cape Province of South Africa, in a search for predatory mites that could have potential for introduction into Australia as biological control agents of redlegged earth mite Halotydeus destructor (Penthaleidae). A total of over 1200 specimens was examined, and 56 species of predatory mites belonging to 14 families were found. Information is presented for 33 known species, including synonymy and bibliography, geographic distribution, and biology where known. Eight species in six families are described as new¨®Bdellodes edentata sp. nov. (Bdellidae), Hypoaspis calcarata sp. nov. (Laelapidae), Hypoaspis muellerae sp. nov. (Laelapidae), Macrocheles propinquus sp. nov. (Macrochelidae), Gamasiphoides lootsi sp. nov. (Ologamasidae), Gamasiphoides rykei sp. nov. (Ologamasidae), Pachylaelaps meganalis sp. nov. (Pachylaelapidae), and Rhagidia meyerae sp. nov. (Rhagidiidae). Fifteen species could not be fully identified because suitable specimens were not available. Of the 41 species that could be identified, nine are already present in Australia. A further 20 species are not known from Australia, but were rare in South Africa and therefore unlikely to be useful predators. Twelve species occurred in significant numbers in South Africa and are not known from Australia. Most of these are known or believed to be generalist predators, and are therefore unlikely to be approved for introduction into Australia. Chaussieria capensis (Anystidae) was considered to have potential and has been studied further. The survey did not identify any other species that were considered to be suitable as biological control agents.

scholarly journals First Screening of Entomopathogenic Nematodes and Fungus as Biocontrol Agents against an Emerging Pest of Sugarcane, Cacosceles newmannii (Coleoptera: Cerambycidae)

Insects ◽  
2019 ◽  
Vol 10 (4) ◽  
pp. 117 ◽  
Author(s):  
Marion Javal ◽  
John S. Terblanche ◽  
Desmond E. Conlong ◽  
Antoinette P. Malan
Keyword(s):  
South Africa ◽  
Biological Control ◽  
Chemical Control ◽  
Entomopathogenic Nematodes ◽  
Biocontrol Agents ◽  
Sugar Production ◽  
Biological Control Agents ◽  
Sugarcane Stalk ◽  
Reduce Sugar ◽  
Steinernema Yirgalemense

Cacosceles newmannii (Coleoptera: Cerambycidae) is an emerging pest of sugarcane in South Africa. The larvae of this cerambycid beetle live within the sugarcane stalk and drill galleries that considerably reduce sugar production. To provide an alternative to chemical control, entomopathogenic nematodes and fungus were investigated as potential biological control agents to be used in an integrated pest management system. The nematodes Steinernema yirgalemense, S. jeffreyense, Heterorhabditis indica, and different concentrations of the fungus Metarhizium pinghaense were screened for efficacy (i.e., mortality rate) against larvae of C. newmannii. The different biocontrol agents used, revealed a low level of pathogenicity to C. newmannii larvae, when compared to control treatments.

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