Assessment of pesticide use and application practices in tomato based agrosystems in Kaliluni sub location, Kathiani district, Kenya

Pesticides are of great benefit to agriculture in Kenya by decreasing crop losses due to insects, weeds, plant diseases, rodents and other pests. They also save lives through control of disease carrying insects and increase the quality and quantity of agricultural produce. However, pesticides are poisons and can affect human health and contaminate the environment. This paper reports on the findings of an assessment of pesticide use, application and practices in Kaliluni, Kathiani district in Kenya. The dominant activity in the area is intensive irrigated tomato farming for local and other markets. Due to the sensitivity of the crop to pests invasion and abrupt changes in temperature pesticides and other agrochemicals are in rampant usage. The area has over 400 households that engage in tomato farming. A total of 72 households were involved in a cross‐sectional survey to assess the pesticides usage, frequency of application, in small holder tomato production. Structured pre‐tested questionnaires were administered through personal interviews and focused group discussion among the tomato farmers in the study site. The aim of the study was to establish whether banned or restricted pesticides were still in use. The study showed that the pesticides used in the region include pyrethroids, organophosphates and carbamates. It was found that 36.8% of the respondents used and applied pyrethroid formulated pesticides while 31.5 % applied carbamate based pesticides. It was also found that some respondents used more than one pesticide in one application. The study also showed that 26.4% of the respondents applied Dithane M45 (fungicide) as their main pesticide while 13%, 12% and 12% used Karate (insecticide), Ridomil (fungicide) and Bestox (insecticide) respectively. Surprisingly 1.9% of the respondents used and applied Dimethoate (insecticide) whose use has been restricted for use in fruits and vegetables while 0.5% used and applied Mocap (insecticide) which has also been banned. The farmers who used the banned chemicals claimed that they were more effective than the other pesticides. On the frequency of application of pesticides, the study showed that 86.1% of the respondents used pesticides on weekly basis whereas 12.5% apply fortnightly. The study therefore recommend that strict measures be taken to safeguard the environment and human health by the enforcing the law on use of pesticides.Key words: Pesticides, carbamates, pyrethroid, dimethoate, Kathiani, Agrosystems, tomatoe

New antitrypanosomal tetranotriterpenoids from Azadirachta Indica

Organic extracts of the leaves of Azadirachta indica A. Juss. yielded ten antitrypanosomal terpenoids. Three of these (1 – 3), are novel and are derivatives of nimbolide and nimbin. They were extracted from chloroformfraction of methanol extract. These compounds were found to exhibit strong antitrypanosomal activities against Trypanosoma brucei rhodesiense with MIC values ranging of 6.9, 15.6 and 7.8 μg/ml respectively and were more active than Cymerlarsan ( a standard drug), which had an MIC value of 187.5 μg/ml when tested against T. b. rhodesiense The structures were elucidated by spectroscopic methods including; NMR, MS, UV and IR.Key words: Meliaceae, limonoids, Trypanosoma brucei rhodesiense, Azadirachta indica, antitrypanosomal activity

The African Landscape through Space and Time

It is generally accepted that Cenozoic epeirogeny of the African continent is moderated by convective circulation of the mantle. Nevertheless, the spatial and temporal evolution of Africa's “basin-and-swell” physiography is not well known. Here we show how continental drainage networks can be used to place broad constraints on the pattern of uplift through space and time. First, we assemble an inventory of 710 longitudinal river profiles that includes major tributaries of the 10 largest catchments. River profiles have been jointly inverted to determine the pattern of uplift rate as a function of space and time. Our inverse model assumes that shapes of river profiles are controlled by uplift rate history and modulated by erosional processes, which can be calibrated using independent geologic evidence (e.g., marine terraces, volcanism and thermochronologic data). Our results suggest that modern African topography started to develop ∼30 Myr ago when volcanic swells appeared in North and East Africa. During the last 15–20 Myr, subequatorial Africa was rapidly elevated, culminating in the appearance of three large swells that straddle southern and western coasts. Our results enable patterns of sedimentary flux at major deltas to be predicted and tested. We suggest that the evolution of drainage networks is dominated by rapid upstream advection of signals produced by a changing pattern of regional uplift. An important corollary is that, with careful independent calibration, these networks might act as useful tape recorders of otherwise inaccessible mantle processes. Finally, we note that there are substantial discrepancies between our results and published dynamic topographic predictions

Determination of L-Ascorbic Acid in Various Kenyan Fresh and Processed Fruits and Vegetables by High Performance Liquid Chromatography

Liquid chromatography methodology for determination of L-ascorbic acid (L-AA) in fresh and processed fruits and vegetables has been developed. The method uses a C18 column and an RP-18 precolumn for the stationary phase. The high-performance-liquid-chromatographic solvent is 0.1M phosphate buffer (pH=6). The flow rate is 2.0 ml/min, and UV detection at 273 nm. Ten different varieties of fruits, 13 different varieties of vegetables, 13 different types of processed fruits and 4 different types of commercial soft drinks were analysed. Results obtained show that Ribena contains the highest (410.0 mg/100 ml) mean level of L-AA while Hey-ho has the lowest (3.8 mg/100 ml). Journal of Agriculture, Science and Technology Vol. 2 (1) 1999: 22-3