Emerging and new pests under climate change in Limpopo Province, South Africa.

Doctor of Philosophy in Crop Science. University of KwaZulu-Natal, Pietermaritzburg 2018.Vegetable production is constrained by pests such as weeds, insects and diseases. The damage caused by pests and diseases can be highly exacerbated by climatic changes and variability. Poor agricultural practices play a role in increasing greenhouse gas emissions which contribute to climate change. Climatic factors such as increased temperature, increased carbon dioxide levels and erratic rainfall are responsible for influencing pest distributions, pest migration and increased pest population. Distribution and migration of pests can also result from globalization, trade and movement of people. Poor biosecurity and phytosanitary measures are also involved in bringing new pests in countries. This study was conducted in Limpopo Province in four municipalities of Vhembe District (Mutale, Musina, Makhado and Thulamela). Quantitative and qualitative techniques were used in data collection. Data was collected through questionnaire surveys, focus groups discussions and key informants. Farmers were randomly selected from a list provided by extension officers in each municipality. Three focus groups were conducted in each municipality consisting of seven women, seven men and a combined group of seven men and women. Statistical Package for Social Sciences (SPSS) was used to compare mean differences between different variables. Means and significant differences between means were declared at P ≤ 0.05. The aim of this study was to evaluate the presence of new and emerging pests in Limpopo Province. The major objectives of the study were to evaluate farmer’s perception on climate change and new and emerging pests, to determine the control measures used by farmers to manage vegetable insect pests, to evaluate the role of institutions on insect pest management, and to determine new and emerging pests in the district. Results of the study indicated that long dry spells, late rainfall and warmer winters were major indicators of climate change in Limpopo Province. Famers in all municipalities perceived aphids as major problematic insect pests to vegetables and were not significantly different from each other (P > 0.05). The highest percentage of aphid prevalence was found in Mutale municipality (82.1%) and the lowest was found in Thulamela municipality (66.7%). Tuta absoluta (South American tomato pinworm) and Spodoptera frugiperda were reported as new insect pests in Vhembe District. Tuta absoluta was only reported in Musina municipality. Spodoptera frugiperda was significantly higher in Makhado irrigated system (72%) and was significantly different from Musina municipality (8.3%) and Thulamela dryland system (19%). Bagrada hilaris (bagrada bug) and Acanthoplus discoidalis (armoured bush cricket) were observed as emerging pests in the district. Thulamela dryland system (73%) was significantly different from Thulamela irrigated system (33%) and Musina municipality (41%) in terms of Bagrada hilaris prevalence. Musina municipality (50%) was significantly different from the rest of the municipalities with respect to Acanthoplus discoidalis prevalence (P < 0.05). The lowest prevalence of amoured cricket was found in Mutale irrigated system (9.52%). All municipalities showed that they highly depended on chemical control for pest management. All municipalities except Makhado dryland system, mentioned that chemicals were effective for insect pest management. The percentage of farmers who agreed that chemicals were effective was significantly different from farmers who did not agree that chemicals were effective (P < 0.05). The overall study showed that climatic factors increased the prevalence of insect pests in Limpopo Province. High temperatures could have influenced the population and distribution of insect pests. New insect pests observed seemed to have quickly adapted to climatic factors in Limpopo Province and therefore, resulted to severe damage on host crops. The study also emphasized that chemical control was effective for insect pest management. However, farmers were over applying pesticides to kill insect pests. This resulted in high levels of pesticide resistance. Frequent application of pesticides can be harmful to the environment and to human health, and can also increase the level of pesticide residues on vegetables. More studies need to be conducted on the biology of new and emerging insect pests in Limpopo Province. Awareness on new and emerging insect pests must be raised to assist farmers in preparedness on how to manage insect pests. Farmers need to be trained more on chemical control measures and other control measures such as integrated pest management and biological control for pest management. The government should also train extension officers on climate change and insect pests, climate smart agriculture and effects of pesticides in order to deliver relevant advisory services to farmers

Screening of cover crops under conservation agriculture.

Master of Science in Crop Science. University of KwaZulu-Natal, Pietermaritzburg 2016.The practice of conventional tillage results in land degradation, reducing soil fertility due to soil erosion. Conservation agriculture aims at reducing soil disturbance which brings benefits of soil conservation. The call for promoting conservation agriculture in South Africa is important in order to reduce the negative impacts caused by frequent conventional soil tillage. Weeds compete for water, nutrients and light with the grown crops. The use of herbicide application to manage weeds has also become problematic due to herbicide resistance that has arisen. However, weed management remains one of the greatest problems that smallholder farmers are facing under conservation agriculture in South Africa. As such there is a need to introduce alternative methods that can be used to manage weeds under conservation agriculture without severe soil disturbances. The study was done in two contrasting agro ecological zones of KwaZulu-Natal, Bergville and Ukulinga. This study was aimed at evaluating three different cover crops for weed suppression and soil macrofauna abundance under conservation agriculture. Vigna unguilata (L.) Walp (cowpea), Lablab purpureus (dolichos lablab) and Mucuna prureins (L.) (velvet bean) were also evaluated for biomass production. The experiment was conducted in a randomised complete block design replicated three times. Herbicide treatment and bare plot served as controls. The data was analysed using the Genstat Stastical Package 17th edition. Poison distribution was used to analyse the soil macrofauna species abundance. Velvet bean produced the highest biomass in both Ukulinga (1.59 t/ha) and Bergville (0.72 t/ha). Cowpea had the lowest biomass accumulation in Bergville (0.59 t/ha) and lablab was the lowest in Ukulinga (0.88 t/ha). Lablab was effective in weed suppression in Bergville (P<0.05). Cowpea performed best in weed suppression in Ukulinga (P<0.05). Lablab showed to be the best in reducing weed species diversity and cowpea showed to be the best in reducing weed species diversity in Ukulinga. Cowpea showed to be effective in improving soil macrofauna abundance in Bergville with (39 species counts). Lablab proved to be the best in improving soil macrofauna species abundance in Ukulinga (57 species counts). Cowpea and lablab showed to be the highest in improving soil macrofauna diversity in Bergville. Lablab and Mucuna pruriens had the highest soil macrofauna species diversity in Ukulinga. It can be concluded that cowpea and lablab can be recommended for use under conservation agriculture to suppress weeds and to improve soil macrofauna species abundance and diversity in South Africa. Farmers will also improve their profit due to reduced herbicide use for weed control