Rapid human population growth has increased food demand worldwide (Tilman et al. 2011, Popp et al. 2013, Maksymiv 2015, Gill and Garg 2014, Jallow et al. 2017, Majeed 2018) which has triggered agricultural intensification (Majeed 2018) yet pests affect crop yields to a great extent (Zanella et al. 2012, Munawar and Hameed 2013); they destroy 30–48% of world’s food yields every year; for instance, in 1987 one third of the potential world crop harvest was lost to pests (Tano 2011). Crop yield losses are a food security threat and pests continue to affect crop yields (Munawar and Hameed 2013). To reduce on food loss, pesticide use has been intensified; however, indiscriminate pesticide use can harm humans and the environment (Majeed 2018). Also, haphazard pesticide application in food crops may compromise food quality, affect prices especially in international food markets, lead to complete refusal due to poor quality products as a result of pesticide contamination. Higher amounts of mixed agrochemicals in food stuffs may result from indiscriminate pesticide use and hence such practices call for better pesticide use regulation.
According to Knight and Norton (1989), improper pesticide-use could result in water pollution and food contamination, endangering human health and non-target species. Improving pesticide practices and reduced pesticide use is beneficial to everyone and the environment (Bon et al. 2014). Alternative non-chemical pest management methods include, among others, biological control and mechanical control (nets and traps), which have shown positive results in various studies from African countries (Bon et al. 2014, Vidogbena et al. 2015). However, a knowledge gap about their use and efficacy still exists especially in small scale farming for example in low scale vegetable production.
Vegetables constitute a major food component and source of income in many parts of the world; they produce higher returns per unit area and time (Ragini 2015) and are consumed as side dish (Grubben and Denton 2004). Vegetable consumption ensures adequate dietary supply of vitamins, minerals, water, and dietary fibre (Sinyangwe et al. 2016). An adult is recommended to consume 400 grams of vegetables daily for a healthy life (Smith and Eyzaguirre 2007, JICA 2016). To cope with the increasing vegetable demand, and reduction in crop loss, pesticides are used especially in vegetable growing to increase productivity, protect nutritional integrity, facilitate storage to ensure year-round supplies, and provide attractive vegetable products (Chow 2016).
Different pesticides can be used depending on the plants and pests involved (Schwinn 1988, Özkara et al. 2016); they are generally described as: insecticides (organophosphates, organocarbamates, organochlorines, pyrethrins and pyrethroids) and fungicides (thiocarbamates, dithiocarbamates) (Fouche et al. 2000, Fait et al. 2001, Fenik et al. 2011). There is widespread use of pesticides in most developing countries (Ohayo - Mitoko 1997) where some farmers apply them indiscriminately which raises concern over food safety (Perez et al. 2015) and health consequences of excessive pesticide use on consumers’ safety and the environment in general which require country governments to revise pesticide residue standards (Okello and Swinton 2011).
A study carried out in Bangladesh on use of pesticide and its impact on health of farmers showed that among the three pesticide groups: organophosphate, organocarbamate and synthetic pyrethroids used in the country, synthetic pyrethroids caused the least harm. Farmers did not always follow the appropriate methods of pesticide use and the waiting period to harvest vegetables (Miah et al. 2014). Pesticide use malpractices are a food safety challenge and the limited information on pesticide use practices in sub-Saharan Africa motivated this study.
Small-scale farmers in several African countries used insufficient personal protection equipment and unsafe pesticide handling practices (Naidoo et al. 2010). Poor pesticide practices were attributed to lack of knowledge about side effects and failure to follow instructions on pesticide usage (Bon et al. 2014). Pesticide application malpractices included use of unregistered pesticides, inappropriate dosage, lack of adherence to pre-harvest interval, use of banned pesticides, inappropriate use of pesticides such as inappropriate pesticide/crop combination and the use of a mixture of different pesticides in a single spray (Ngowi et al. 2007, Marčić et al. 2011, Nonga et al. 2011, WHO and IPCS 2010). There is insufficient data on pesticide use practices in Uganda hence a need for this study.
A study conducted by Oesterlund et al. (2014) revealed the extent of pesticide use by small-scale farmers in Uganda and examined the knowledge, practice and impact of protective measures and the storage of pesticides and attitudes. The study showed that the most frequently used pesticides belonged to World Health Organization (WHO) class II. Farmers had limited knowledge about pesticide toxicity, did not use appropriate personal protection equipment or good hygiene when handling pesticides, it was important to assess whether the status had changed since then.
Misuse of pesticides was observed in Mindu dam, Tanzania (Mdegela et al. 2013) where majority of the farmers re-packed pesticides locally in small quantities in improvised containers without safety instructions for use and handling. Mixing pesticides in knapsack sprayers was also a common practice. This creates a potential risk of the pesticide residues in the crops which can affect food quality and eventually consumer health. There are reports of inappropriate dosages and application rates of pesticides in vegetable farming for instance, a study in Mang’ola District, Tanzania reported that farmers apply pesticides on vegetables at over-dosage levels (Mhauka 2014). Other studies in the Manyara basin and Arumeru District, country showed that farmers applied pesticides on vegetables on a routine basis as a means of protection even though no pest had been observed on the plants (Ngowi et al. 2007, Nonga et al. 2011). This can result in unnecessary production costs and/or unacceptable pesticide residues in the vegetables.
The attention of populations in sub-Saharan Africa (SSA) on vegetables as vital dietary components reinforces the significant roles that leafy vegetables have long held as important components in African diets; they are indispensable ingredients of soups or sauces that accompany carbohydrate staples (Chweya and Eyzaguirre (Eds.) (1999). An average of 10% of the food budget is spent on fruits and vegetables in various African countries (Joosten et al. 2015).
Vegetables grown across Africa include bottle gourd (Legenaria vulgaris), cabbage (Brassica oleracea var. capitata), cauliflower (Brassica oleracea), carrot (Daucus carota), fluted pumpkin (Telfairia occidentalis), potato (Solanum tuberosum), egg-plant (Solanum aethiopicum), spinach (Spinacia oleracea), sweet pepper (Capsicum annum), water leaf (Talinum triangulare), tomato (Lycopersicon esculentum), and bitter leaf (Vernonia amygdalina). Others include Celosia argentea, amaranths, Abelmoschus esculentus, Capsicum spp. Daucus carota, Allium cepa, Alium sativum, Musa spp, Moringa oleifera, Zathoxylum zanthoxyloides, Telfairia occidentalis, Talinum traingulare, Venonia amygdalina, Lecaniodisus capaniodes, Corchorus olitorius, Piper guninensis, Tamarindus indica, Vigna unguiculata, Basella alba, Crassocepholum, rubens, Cassia occidentalis, Amaranthus palmeri, Bidens pilosa, Urticadiocia, Phaseolus vulgaris, Pisum sativum, Solanum scrabrum, Crotalaria ochroleuca, Vigna unguiculata, Cynara scolymus, Cynara cardunculus, Allium porum, Raphanus sativus, Apium graveolens, Cucumis sativus, Citrullus lanatus, Asparagus officinalis (Ogwu et al. 2016).
Commonly used pesticides in vegetables worldwide include dichlorvos, phorate, cypermethrin, diazinon, fenitrothion, malathion, parathion, profenofos, ethion, acephate, aldrin, captan, chlorpyrifos, dieldrin, disulfoton, endosulfan, fenthion, methoxychlor, parathion-methyl, methamidophos, Bitertanol, carbendazim, flusilazole, hexythiazox, imidacloprid, methidathion, methiocarb, pyriproxyfen and trichlorfon, cyromazine, melamine, thiabendazole, iprodione, vinclozolin, azinphos-methyl, dimethoate, Isofenphos-methyl, isocarbophos, phosalone, phosmet, phosphamidone, pretilachlor, propoxur, pymetrozine, simazine, terbuthylazine, terrazole, thifluzamide, parathion-ethyl, and dicarboxamide, chlorpyrifos-methyl organophosphate, metalaxyl, phenylamide, malathion organophosphate, fenthion organophosphate, phosmet organophosphate, monocrotophos, omethoate, oxydemeton-methyl, vamidothion, iprodione, Isopropoxyphenol, naphthol, carbofuran, propham, propoxur, carbaryl, aldicarb, sulfoxide, methomyl, phenanthrene, 4-nitrophenol (Fenik et al. 2011).
Indiscriminate pesticide use in food crops may leave pesticide residues in food beyond concentrations considered safe for consumption (Miah et al. 2014, Okonya and Kroschel 2015, Jallow et al. 2017). According to EUs Pesticide Action Network, (2008), 350 different pesticides were detected in food produced in the EU. More than 5% of food products contained pesticides at levels exceeding the EUs maximum permitted level (MPL) (Fenik et al. 2011); there is limited information on the status of food produced in Uganda yet occurrence of pesticide residues in food is a threat to food security due to the health risks associated with consumption of tainted food (Miah et al. 2014).
While information on the most commonly used pesticides Uganda is scarce most farming is done on small-scale farmers where farmers have less than a few acres of land per household and often farm without appropriate means or knowledge to use pesticides (Salameh et al. 2004, Jors et al. 2006). In the absence of appropriate handling of pesticides, not only the health of farmers, but also the health of their families is at risk (Macfarlane et al. 2008, Sam et al. 2008, Williamson et al. 2008). This study therefore was aimed at investigating the commonly grown vegetables, the common pesticides used in vegetables spraying and the knowledge of farmers on pesticide application practices in Kabale District, Uganda.