Farmers’ ethno-ecological knowledge of vegetable pests and pesticidal plant use in Malawi and Zambia

While pests are a major constraint in vegetable production in many parts of Southern Africa, little is known about farmers’ knowledge and management practices. A survey was conducted among 168 and 91 vegetable farmers in Northern Malawi and Eastern Zambia, respectively, to evaluate their knowledge, attitudes and traditional management practices in tomato and crucifers (brassica). All respondents in Malawi and Zambia reported pest damage on tomato and crucifers, and 75% had used synthetic pesticides. The use of pesticidal plants, cultural practices and resistant varieties constituted a smaller portion of the pest control options in both crucifers and tomato. Over 70% of the respondents were aware of pesticidal plants, and more female (75%) than male (55%) respondents reported using them. While over 20 different plant species were mentioned by respondents, Tephrosia vogelii accounted for 61 and 53% of the pesticidal species known to respondents in Malawi and Zambia, respectively. Farmers with small landholdings were more inclined to use pesticidal plants than those with medium and large landholding highlighting the importance of this management alternative for poor farmers. Most respondents were willing to cultivate pesticidal plants, which indicate that farmers understand the potential value of these plants in pest management

Maize productivity and profitability in Conservation Agriculture systems across agro-ecological regions in Zimbabwe: A review of knowledge and practice

Conservation agriculture (CA) is increasingly promoted in southern Africa as a strategy to improve food security and reverse soil degradation in the face of climate change. However, the performance of CA under different environments and its ability to improve ecosystem services is still unclear. The effects of the CA options; direct seeding, rip-line seeding, and seeding into planting basins on maize grain yield, soil health and profitability across agro-ecological regions in Zimbabwe were evaluated through a review of literature in combination with meta-analysis. Overall, CA improved maize yield over conventional agriculture. Compared to conventional agriculture, direct seeding, rip-line seeding, and seeding into planting basins increased yield by 445, 258 and 241 kg ha−1, respectively. However, there was an initial yield decline in the first two years. CA practices reduced soil erosion and bulk density, and increased soil water content in most studies. Under high levels of residue retention (6 Mg ha−1), CA systems exhibited greater macro fauna abundance and diversity than conventional agriculture, particularly termites. Weed pressure tended to increase labour requirement for hand-hoe weeding under CA compared to conventional agriculture. However, the use of herbicides reduced weeding labour demand during the early season. The benefits of CA are tied to the farmers’ management intensity including: time of planting, weeding, fertiliser and herbicide application, and adequate training on equipment use. Economic analysis results showed that on average, a farmer incurs losses for switching from conventional agriculture to CA in the main maize growing regions of Zimbabwe. Based on the six seasons’ data, the losses were least with the ripper in drier areas and worst with the direct seeder in wetter areas. Incorporation of chemical herbicides worsens the economic returns of CA tillage options in all the agro-ecological zones. Overall, the study showed that the rip-line seeding is more attractive in the drier areas than direct seeding. Although not costed in this study, critical is the cumulative reversal of soil degradation associated with consistent CA practice which can sustain agriculture. Results from this review suggest that the benefits of CA depend largely on the type and context of CA being practised. It is thus imperative to profile the technology, the farmer socio-economic circumstances and the bio-physical environment in which the farmer operates for proper geographical and beneficiary targeting to achieve greater impact. More longer-term studies are required to fully elucidate the benefits and context of CA options and practice

Chemical variation and insecticidal activity of Lippia javanica (Burm. F.) Spreng essential oil against Sitophilus zeamais Motschulsky

Lippia javanica (Burm. f.) Spreng is used commercially as an herbal tea and medicinal plant in sub-Saharan Africa. Here we investigated the chemical variation and pesticidal potential of L. javanica essential oils against a major stored product pest, Sitophilus zeamais Motschulsky. We identified two morphologically distinct varieties of L. javanica growing at different locations in Malawi. Perillaldehyde was the major constituent in oil of L. javanica var. javanica while myrcenone (ipsdienone) was the major compound in oils of L. javanica var. whytei. Myrcene, linalool, carvone, β-caryophyllene and germacrene D were identified as the other most significant components in oils from both varieties. The yields of oil and the chemical composition also varied significantly with time of harvest during the season in both cases. In contact toxicity tests against S. zeamais, oils from both varieties were active. However, whereas perillaldehyde, linalool and carvone, components of the oil of L. javanica var. javanica, were all toxic against adult S. zeamais, myrcenone, the main component of oil from L. javanica var. whytei, was not. The oil from L. javanica var. javanica also showed some fumigant toxicity against S. zeamais. The high efficacy of L. javanica oil against S. zeamais suggests it is suitable to be used as a botanical insecticide to control S. zeamais in stored maize. However, further research is required to optimise and standardise the variety and harvest time to be recommended and to evaluate its activity against S. zeamais and other storage insect pests under farm conditions before it can be adopted by farmers more widely

Tick control measures from nature

Scientists from the Universities of Zimbabwe and Greenwich delved into the possibility of using fever tea (Lippia javanica) for cattle tick control in Zimbabwe. Here are their findings

Cattle tick control in Africa: potential of ethnoveterinary plants.

Cattle are a livelihood asset to smallholder farmers in Africa yet remain threatened by the effects of ticks and tick-borne diseases during production because they cause morbidity and premature death. The use of indigenous plants in tick control is a worldwide practice spanning thousands of years. Changes in the agricultural and socio–cultural landscape over time have, however, led to neglect of indigenous pesticidal plants in favour of synthetic products. The benefits of synthetic acaricides are well-recognized, but emerging observation indicates that they cannot solve all livestock health problems across production systems, farmer circumstances and agro-ecologies. Concerns associated with commercial acaricides have revived research interest in alternative or complementary remedies. Past research has focused on documenting ethnoveterinary practices, scientific validation of the practices and optimization of these practices. Here, we review the challenges of synthetic acaricides and progress made in ethnoveterinary plant research and development in Africa. The review highlights challenges of access, affordability and availability of commercial acaricides to resource-poor communities; synthetic acaricide resistance development; disposal of obsolete acaricides and environmental pollution; reduced water supply and implications on conventional use of acaricide-treated dipping facilities; and plant bioprospecting and downstream development of products in Africa. This information contributes towards shaping the ethnoveterinary plant research agenda and policy, and investment interventions in Africa

Effect of moringa extract on the leaf anatomy and yield potential of tomato infected by Alternaria solani

Tomato is often exposed to hormones and diseases, among other factors, to which responses in leaf anatomy and yield are observed. This study evaluated responses in the leaf anatomy of Alternaria solani infected (IN) and non-infected (NIN) tomato (Solanum lycopersicum) to moringa leaf extract (MLE) application; the responses were then correlated with fruit yield. MLE concentrations of 0.5, 0.75 and 1.5 kg L−1 (w/v) were prepared. Controls were distilled water (negative) and 50 mg L−1 benzylanimopurine cytokinin (positive). Significant interactions were observed for stomatal density (p < 0.001). MLE increased lamina thickness, stomatal density, stomatal size and yield. There was a strong positive correlation between yield, stomatal density, stomatal size and lamina thickness. Stomatal density showed the strongest correlation (r = 0.7979) with fruit yield.University of Pretoria, South Africahttp://www.tandfonline.com/loi/tjps202019-06-11hj2019Plant Production and Soil Scienc

Acaricidal efficacy against cattle ticks and acute oral toxicity of Lippia javanica (Burm F.) Spreng

In search for low-cost, safe and environmentally benign plant-based alternatives to commercial pesticides, the efficacy of Lippia javanica aqueous leaf extracts in controlling ticks on cattle, acute oral toxicity in mice and phytochemistry were evaluated. L. javanica aqueous leaf extracts at 10% and 20% w/v were effective at controlling cattle ticks but not as good as an amitraz-based acaricide Tickbuster®. However, they can provide an effective tick control option where synthetic products are unavailable or unaffordable, particularly in remote parts of southern Africa. Peripheral blood samples collected showed no haemoparasites in treated cattle implying that animals did not suffer from clinical tick-borne diseases. The leaf aqueous extracts of L. javanica were tested for toxicity in BALB/c mice. While anecdotal evidence suggests L. javanica has low mammalian toxicity, within 48 h all mice fed with the L. javanica leaf aqueous extract at 12.5-37.5% v/v were lethargic, and overall mortality was 37.5% (n = 24). Thus, despite their apparent safety, water extracts of L. javanica leaves may have deleterious health implications on humans and animals if consumed at very high doses. Many compounds have been identified from L. javanica including an array of phenolic glycosides, flavonoids and essential oils but none of these are known to have acute toxic properties