Tomato post-harvest spoilage, causes and use of selected botanical extracts in their management in Mwea, Kirinyaga County
Tomato is an important vegetable crop in Kenya. It is widely grown for home consumption and for sale. The demand for fresh tomato is high both for domestic use and markets. However, tomato post-harvest losses are a threat to the harvested tomatoes. There is no well documented current knowledge on the nature and status of post harvest losses on tomato in Kenya particularly with regard to pests and diseases. In areas where post-harvest losses have been documented the figures vary considerably such that their usefulness is short lived. Periodic surveys are therefore necessary to help understand the severity of losses in a specific place at a specific time. The aim of this study was to carry out a survey on the post-harvest losses of tomato in Mwea, Kirinyaga county and document pests and diseases contributing to the same. The study also aimed at evaluating the efficacy of some selected plant crude extracts against four major post-harvest tomato damaging pathogens. The target tomato cultivars were those commonly grown by the farmers in the target areas. A survey was carried out to access the current status and causes of post-harvest losses. Factors such as cultivar disposition to diseases, means of transport to the market, distance to the market, source of labour for harvesting, packing containers, time lag in the market, pest and disease attacks were investigated. Disease causing micro-organisms that were suspected to cause the post-harvest damage were isolated, identified and re-inoculated to wounded surface sterilized fresh harvested ripe tomato to establish pathogenicity. Crude plant extracts from neem leaves, garlic bulbs and ginger rhizomes were tested for the control of the most potent fungal and bacterial pathogens. An in vivo experiment was carried out where healthy ripe tomato fruits were dipped into the selected crude plant extracts and disease development on them monitored and compared with the untreated tomato samples. Data was analysed using SPSS and SAS One way ANOVA and means separated using Students – Newman – Kuels Test. The survey revealed that factors such as means of transport to the market, packing containers, decay of fruits and time lag in the market differed significantly (p<0.001) and contributed to post-harvest losses that averaged 30.63%. Seven pathogens were isolated from infected tomato samples and they varied significantly (p<0.001) with Furasium spp. being the most prevalent (30%). Damage caused by the pathogens on tomato fruits also varied significantly (p<0.001) with Rhizopus spp. causing (100%) rot. Plant extracts were tested for their efficacy in controlling four most damaging pathogens where their efficacy differed significantly (p<0.001) with garlic extracts being the most effective. The in vivo study demonstrated that the extracts could be applied to control the rots on the tomato fruits. Results of this study showed that plant extracts had antimicrobial compounds such as linalool, geraniol, nimonal, diallyl disulphide, azadrachtin that acted against the test pathogens and can be an important step in developing plant based bio-pesticides for the management of fruit rots because the plants are readily available, affordable and environmental friendly. The study recommends that farmers shorten the distance between harvesting and collection time to reduce chances of fruit exposure to the pathogens.