Evidence of African horse sickness virus infection of Equus zebra hartmannae in the south-western Khomas Region, Namibia.

Equine mortalities suspected to be due to African horse sickness (AHS) were reported from the arid Khomas Region, Namibia, in 2008. The area was previously considered a localized AHS-free area. Hartmann's mountain zebra (Equus zebra hartmannae), a potential but unconfirmed reservoir host of African horse sickness virus (AHSV), occurs in the region. Between 2009 and 2010 serum, blood and tissue samples from 31 culled E. z. hartmannae were analysed by reverse transcription-polymerase chain reaction (RT-PCR) (n = 31) and enzyme-linked immunosorbent assay (ELISA) (n = 18) to determine the presence of AHSV and/or antibodies against AHSV. The presence of antibodies against AHSV was demonstrated in all 18 samples assayed, and AHSV double stranded RNA was detected in 26% of the animals. This is evidence that E. z. hartmannae can become infected with AHSV.

Comparative diversity of arthropods on Bt maize and non-Bt maize in two different cropping systems in South Africa.

The biodiversity of an agroecosystem is not only important for its intrinsic value but also because it influences ecological functions that are vital for crop production in sustainable agricultural systems and the surrounding environment. A concern about genetically modified (GM) crops is the potential negative impact that such crops could have on diversity and abundance of nontarget organisms, and subsequently on ecosystem functions. Therefore, it is essential to assess the potential environmental risk of the release of a GM crop and to study its effect on species assemblages within that ecosystem. Assessment of the impact of Bt maize on the environment is hampered by the lack of basic checklists of species present in maize agroecosystems. The aims of the study were to compile a checklist of arthropods that occur on maize in South Africa and to compare the diversity and abundance of arthropods and functional groups on Bt maize and non-Bt maize. Collections of arthropods were carried out during two growing seasons on Bt maize and non-Bt maize plants at two localities. Three maize fields were sampled per locality during each season. Twenty plants, each of Bt maize and non-Bt maize, were randomly selected from the fields at each site. The arthropods collected during this study were classified to morphospecies level and grouped into the following functional groups: detritivores, herbivores, predators, and parasitoids. Based on feeding strategy, herbivores and predators were further divided into sucking herbivores or predators (piercing-sucking mouthparts) and chewing herbivores or predators (chewing mouthparts). A total of 8,771 arthropod individuals, comprising 288 morphospecies and presenting 20 orders, were collected. Results from this short-term study indicated that abundance and diversity of arthropods in maize and the different functional guilds were not significantly affected by Bt maize, either in terms of diversity or abundance.

The impact of insecticides on beneficial arthropods in cotton agro-ecosystems in South Africa.

The unique diversity of beneficial arthropods in South Africa can be regarded as an important natural resource in agro-ecosystems as it plays an important role in the natural control of insect pests. Insecticide applications reduce the ability of these beneficials to regulate cotton pests. In the absence of insecticides, average daily predation rates of 37% and 30% of bollworm eggs and larvae respectively were found in exclusion experiments. By minimizing the number of pesticide applications the combination of the direct negative effect of pesticide application on predator populations and secondary pesticide effects such as the stimulation of red spider mite populations as a result of predator suppression, can be avoided. This would open the option to fully utilize the full pest control potential of the natural enemy complex.