Mwanarusi Saidi

Repellent Effect of Alphacypermethrin-Treated Netting Against Bemisia tabaci (Hemiptera: Aleyrodidae)

ABSTRACT For >20 yr, Bemisia tabaci Gennadius persists as a begomovirus vector and is a serious problem in tomato production in many parts of the world. In tropical countries, the use of netting to protect horticultural crops has proven to be an effective and sustainable tool against Lepidoptera but not against small insects. This study evaluated the repellent effect of AgroNet 0.9T, a 0.9-mm pore diameter and 40-mesh size netting treated with alphacypermethrin insecticide against B. tabaci. This pyrethroid insecticide is known to have toxic and repellent effects against mosquitoes and has been used for treatment of mosquito nets. Two nontreated netting materials were used as control: AgroNet 0.9NT with 0.9-mm pore diameter and 40-mesh size and AgroNet 0.4NT with 0.4-mm pore diameter and 80-mesh size. The behavior of B. tabaci and its parasitoid Encarsia formosa Gahan as they progressed through the treated netting was studied in the laboratory in choice and no-choice tests. The development of wild B. tabaci population on tomato plants protected by the same nets was followed in two field trials implemented in Njoro, Kenya. Results obtained with the no-choice tests showed a significant reduction of movement on the treated net with 40-mesh (19%) compared with nontreated netting (35 and 46% with 80- and 40-mesh, respectively). The mortality of B. tabaci was significantly higher (two-fold) in the test tube containing only the treated netting compared with the nontreated one. The repellent effect of the treated netting was also demonstrated against E. formosa, but it did not have this toxic effect. Unlike for B. tabaci, the treated and nontreated nets appeared to have a similar repellent effect on E. formosa in the choice test, which suggests a learning behavior of the parasitoid. In both field tests, B. tabaci population was significantly lower on tomato protected by the treated net compared with the same nontreated net. However there was no significant difference in B. tabaci population between the treated 0.9-pore diameter and the nontreated 0.4-pore diameter. We discussed these findings and their implications for the use of repellent netting in integrated pest management in horticulture and more specifically in vegetable production.

Does contract farming improve smallholder income? The case of avocado farmers in Kenya

Purpose – Contract farming (CF) is seen as a tool for creating new market opportunities hence increasing incomes for smallholder farmers. Critics, however, argue that CF is likely to pass risks to small scale farmers, thus favouring large scale farmers at the expense of smallholder farmers. The purpose of this paper is to examine the effect of CF on smallholder farmers’ income using a case study of avocado farmers in Kandara district in Kenya. Design/methodology/approach – The study uses data collected from 100 smallholder avocado farmers in Kandara district in Kenya and employs an instrumental variable model (Probit-2SLS) to control for endogeneity in participation in the contract and examine the effect of CF on household, farm and avocado income. Findings – The results indicate that participation in CF is not sufficient to improve household, farm and avocado income. Question remains regarding efficient implementation of CF arrangements to promote spill over effects on other household enterprises. Resear...

Net cover color influence nutritive quality of African nightshade and spiderplant

ABSTRACT Indigenous leafy vegetables play a major role in strategies to attain food and nutritional security for African households. However, the potential of these vegetables in meeting the nutritional requirements have not been adequately exploited. This study assessed effects of shadenets on nutritive value of African indigenous leafy vegetables. The vegetables African nightshade (Solanum scabrum Mill.) and spiderplant (Cleome gynandra L.) and net covers colored white, gray, blue, and yellow, with unnetted plants as a control were used. From the 7th week after sowing (spiderplant) and transplanting (African nightshade) and at 2-week intervals nutritive quality variables were determined. Compared to open field, white net produced higher leaf β-carotene at 13 weeks after planting by 6% and 17% for African nightshade and spiderplant, respectively. Use of blue net cover reduced leaf vitamin C content by 94.5% and 79% in African nightshade and spiderplant, respectively, compared to open field at 15 weeks after planting. Higher leaf calcium was consistently recorded for plants grown under yellow net cover for African nightshade and white nets for spiderplant; but was reduced under blue net for both species on most sampling dates. Leaf iron content was maximized under yellow net cover for both crops. Use of net covers reduced leaf crude fiber content compared to open field; high leaf phenolic content was obtained in crops grown under white net for both vegetables. The crop responses were attributed to spectral quality, light intensity, and environmental changes to which the crops were subjected. The different colored agronet covers differentially influenced crop leaf nutritive quality.

Effect of Coloured Agro-Net Covers on Insect Pest Control and Yield of Tomato (Solanum lycopersicon Mill)

Tomato ( Solanum lycopersicon Mill) is one of the most important vegetable crops consumed throughout the world; and is rich in important vitamins, minerals and antioxidants. Production of the crop in open fields is however constrained by several biotic and abiotic stresses that lead to low tomato yields and quality. This study aimed at determining the effects of coloured agro-net covers on microclimate, pest infestation and yield of tomato cultivar ‘‘Rio Grande’’. The study consisted of two trials conducted using a randomized complete block design (RCBD) with five replications and six treatments. Tomato plants were grown under blue, yellow, grey, white or multi-coloured net covers with a no net cover as the control. Data were collected on microclimate (temperature, soil moisture, relative humidity and photosynthetically active radiation), pest counts and crop yield variables. Net covering modified the tomato crop microclimate with highest temperatures and soil moisture and, relative humidity levels recorded under white (21.03 o C), blue (30.03%) and multi-coloured net covers (76.26%), respectively compared to the no net control treatment (16.32 o C, 14.82% and 64.90%). Photosynthetically active radiation (PAR) was lowest under the blue agro-net cover (416.09 µmol m -2 s -1 ) and highest under control treatment (985.00 µmol m -2 s -1 ). Tomato plants grown under coloured-colour nets (yellow and blue) had lower population of silverleaf whitefly, thrips and aphids while mite population was lower under neutral-colour net covers (white, grey and multi-coloured). The neutral-colour net covers (24938.87, 19525.16 and 21541.93 kg/ha) resulted in higher yields compared to coloured-colour net covers (16804.62 and 14551.05 kg/ha). Results of the study indicate that use of agro-net covers especially the neutral-colour net cover can improve microclimate, protect tomato against insect pests and can be considered a viable strategy for tomato production by smallholder growers.

Adoption of African indigenous vegetables into agro-pastoral livelihoods for income and food security: Evidence from Kenya

Purpose - The purpose of this paper is to determine the factors influencing adoption of African indigenous vegetables (AIVs) into the agro-pastoral farming systems aiming at improving livelihoods. Design/methodology/approach - The paper is based upon the diffusion theory which is linked to the random utility theory. A survey of 205 agro-pastoral households obtained through multistage sampling technique was used. Factors influencing adoption of AIVs were estimated using a logit model. Findings - Findings indicate that the acreage under AIVs was still very low compared to other crop enterprises with the most common types of AIVs grown being Research limitations/implications - Limitations include reliance on respondents’ willingness to provide correct information. Originality/value - This paper adds value in its contribution to literature on diversifying agro-pastoral livelihoods through production of AIVs for income and food security.