Results in Table 2 imply that respondents were able to give reasonable answers in regard to the issues asked under the survey, given categories of their education levels. A wide range of vegetables produced in the area of study focus indicated the level of diversity of vegetable crop production. The high average number of years of vegetable production indicated that farmers had vast knowledge and experience in vegetable farming. High yields motivated farmers for pesticides use, followed by high profit, implying that pesticides reduced risks of crop damage by insects and fungal diseases, the major threat to crop yield, quality and profit; therefore, farmers had a sound reason to use pesticides.
In this study, 100% of farmers visited, faced a problem of pests and diseases in their fields and used pesticides to control them, implying that prevalence of pests and diseases was the driving force for farmers into pesticides use (Tables 3, 4, 5 and 6). Since majority of the farmers managed pests and disease problems by themselves imply that they used knowledge within their means, given that most of them did not receive trainings. Since more than 80% of farmers relied only on pesticide spraying for management and control of pests and diseases and only less than 7% of them used other options in addition to pesticides spraying, imply that the rate of pesticide use in the study area of focus is so high; clearly reported by 100% of farmers who produce the different vegetable crops. This reveals that the overall levels of pesticide use in the area is so significant and the implication is that it could result in the residues accumulating in water sources and food chains, exceeding safe limits and causing overall ecosystem degradation.
High reliance by farmers on chemical spraying as the major option for pest and diseases control, and use of numerous types of pesticides in their fields (Table 4), most times combined in one tank mix indicates there is a high rate and extent of pesticide use in the area; which puts a serious risk to the surrounding forms of biodiversity and entire ecosystem components, such as water resources by residual accumulation and pollution. Notwithstanding the risk of pest and disease resistance to pesticides, likely to result into more pesticides sprays due to continuous pest and disease reoccurrence which puts more risks of pesticide pollution to the environment and spillover effects through water movement, spray drifts and attachment to soil particles.
This study revealed that all farmers who were engaged in producing any vegetable crop did so with use of pesticides (insecticides, fungicides and herbicides) and in each case the usage rate was almost 100%. The implication of this high rate of pesticide use therefore, is the high risk of pesticide residues accumulation of in water, air, soil particles and in the food chain, and high resistance of pests and diseases to pesticides which results into high prevalence of pests and diseases, resulting from mutant strains, causing changes and loses of biodiversity and alterations in ecosystem functions through changes in food webs and food chains. Farmers do not use any organic pesticides; it could be because they are not easily available on the market.
Since the study revealed that some farmers were unable read pesticide labels to determine correct application rates, imply that excessive or lower rates were used by farmers. Common practices revealed were use of arbitrary measures like tablespoons and bottle tops. So, violation of pesticide application procedures was revealed, which results into high or low quantities of pesticides being applied. High pesticide quantities and application frequencies were a response to increased pest and disease problems, as in Okonya et al. (2015). Tomato was the heaviest consumer of pesticides at two routine sprays a week, which most farmers used. Farmers reported, they were not ready to give up the ‘insurance’ against losses, achieved by pesticide use, imply increased pesticide use in the area, moreover in Uganda, particular pesticides formulations were now within the purchasing power of more producers following the removal of the import tax on agricultural chemicals (Karungi et al., 2011).
About 80% of farmers apply pesticides to their vegetable fields; weekly or twice a week means that most farmers apply pesticides more frequently and therefore, more pesticides were frequently pumped into the environment. So, effects of such pesticides (pollution, toxicity) were more likely to be exposed to the surrounding biodiversity and could be felt as both short- and long-term effects. Routine pesticide spraying practiced by more than 90% of the farmers, irrespective of pests and or disease presence, was an indication of incorrect application frequencies of pesticides (twice a week, so on), resulting in unnecessary excess amounts which potentially could increase pesticide residues and pollution in surrounding ecosystems such as water sources.
It was therefore apparent that though spraying pesticides was necessary for increased productivity and quality, aspects of frequency, interval and intensity of pesticides use required desirable knowledge by farmers, since this was likely to cause havoc by accumulating pesticide residues in the different ecosystem components such as water sources, food chains, air among others, hence resulting in ecosystem and biodiversity imbalances. Water and food quality and safety are likely to be affected, and resistance to pesticides by pests and diseases duly likely to exist, if no strategies to regulate frequency, interval and intensity of pesticide application were put in place.
The frequency, intensity and interval of pesticide application keep changing depending on the prevailing weather conditions. During the rainy seasons, different farmers apply pesticide at different intervals ranging from every 3 days, every 4 days, and every 5 days, weekly and above 7 days depending on the type of crop. In dry seasons application intervals ranging from every 4 days, weekly and above 7 days were reported by different farmers. Although both cases had some close intervals of pesticide application, rainy seasons had more pesticides applied to the fields than in the dry seasons. This means, in rainy seasons more pesticides residues accumulate in the ecosystem components such as water sources through run offs and percolation through soil particles, than in dry periods; meaning that more pesticide residues are most likely to be present in water during rainy seasons.
Given that tomatoes consumed more pesticides, in more close intervals both in wet and dry seasons, followed by onion and cabbages, meant that tomatoes, onions and cabbage contributed more pesticide residues to the ecosystem in the respective order. It was realized that synthetic pesticides were intensively used in vegetable farming (especially on Tomato, Onion and Cabbage). Use of pesticides in vegetable production in this study area of focus was dependent upon high pest infestations, prevalence of diseases, and the crop grown. Therefore the more the farmers apply pesticides more frequently (twice a week, weekly) imply that more pesticides are pumped into the environment, whose likely effects may include high residual accumulation and pollution in the ecosystem and serious biodiversity degradation which can have both short and long term effects to biotic elements.
Other research findings have also shown heavy usage of pesticides on tomato in other countries in Africa; Ntow et al., (2006); Karungi 2011 working on tomato in Ghana indicated that farmers sprayed an average of 6–12 times a season, whereas it was 5–16 times or more per cropping season in Tanzania (Ngowi et al., 2007; Lekei et al., 2014; Karungi 2011. Such heavy use of pesticides implies that pesticide residues accumulation levels in the ecosystem components would raise higher, causing water quality loss, biodiversity imbalances, and frequent contact of farmers with pesticides, could lead to significant health problems.
Fungicides are not easily observed to cause serious and acute damage to farmer's health but it has been reported that there is a long-term risk for cancer development and endocrine disruption resulting from farmer's exposure to fungicides containing mancozeb (Novikova et al., 2003; Mpala et al 2016), which can be by direct physical contact, contact through water and food. The dithiocarbamate family of fungicides is also suspected to have reproductive (Restrepo et al., 1990), and mutagenic effects in human cells exposed to it (Pretty and Waibel, 2012, Pretty, 2012).
Findings also revealed the status quo of biotic constraints to vegetable production in the study area, was high and the easiest available pests and disease control measure was spraying synthetic pesticides. Fungicides were the most used because of fungal blights, especially Phytophthora, which were ever-present, and which would result in more than 75% crop losses if not checked; this was in line with Akemo et al. (2000) and Karungi et al. (2011). Farmers responded to the threat by effecting routine/calendar sprays with fungicides, majority of them spraying as often as twice a week.
Although pesticides are useful in fostering the agriculture production, but when improperly used can pose dangerous risks to the entire ecosystem. Therefore, knowledge of the possible entry and effects of pesticides contaminants and pollution to the environment requires in-depth analysis of types of pesticides, application methods, and education levels of the users, pesticide handling and the trainings given to the users.
Information concerning farmer’s awareness in the use and handling of pesticides
Given that only 27.8% farmers seek for knowledge on how to apply pesticides, but majority farmers do not, coupled with inadequate trainings in pesticide use; implies that most farmers used pesticides incorrectly, which increase risks of resultant excessive or inadequate pesticide quantities and might cause increased residual accumulation and pollution of the ecosystem or resistant strains of pests and diseases due to insufficient doses used. Self-decisions by farmers with less pesticide knowledge, implies incorrect use of pesticides resulting in contamination and pollution of the ecosystem components such as water sources. Farmers’ trainings in pesticide use and handling practices were so low compared to the high rate of pesticides use by farmers. However most farmers engaged in vegetable production attained some level of education (Table1), which would implies that, they are able to read instructions on pesticide labels to determine the right application methods, rates of application among others, this is not a guarantee as most farmers did not bother reading instructions while using pesticides.
Bathing and cleansing of spray equipment in water by some farmers; imply a serious risk of reduced water quality due to contamination by pesticides which could build to toxic levels to cause short and or long-term effects. The implication of improper disposal of pesticide containers; for instance, when thrown in water, cause direct water contamination, whereas when thrown to bushes, may still find their way to different ecosystems including water causing contamination and accumulation of pesticide residues in water.
Some farmers were not able to identify expiry dates on pesticide labels, implying that they sometimes applied expired pesticides to their crops, a practice riskier to the crops, the environment and human health. This reflects that majority of farmers did not receive any knowledge from training workshop, seminar or awareness campaigns about pesticide use and handling practices implying high rate of incorrect pesticide usage in the study area, which translates into high accumulation of pesticides residues in the ecosystem, resulting into pollution of the environmental components.
Majority farmers were not able to calibrate their spray equipment to determine right application rates; implying destruction of crops by excessive quantities or pest and or disease resistance to pesticides in case of low quantities which ultimately increases pest populations and continuous crop destruction by resistant disease causing agents. Since use of pesticides for pest management reported as the easiest farmer’s option, implied that more pesticides entered surrounding ecosystem components; however, actual amounts of pesticides used in Uganda were not known. In general, a significantly high use of pesticide on vegetables in the study area exists, implying that; increasing the acreage for vegetable growing potentially increases pesticide use in the area, which results in polluting the ecosystem. Farmers apply pesticides to crops sold to the market, improving quality for cash, and as vegetables increasingly become a staple crop in Uganda’s economy, farmers apply pesticides to safeguard themselves from yield loss. This high use of pesticides results in contamination of the environment including water resources.
Since most farmers mixed pesticides in their fields which were reportedly on hills, with water sources in adjacent valleys, imply that water run offs during rains, from mixing grounds in the fields could end up in the nearby water sources posing a risk of water contamination by pesticides; but also those who reportedly mixed at the water sources, contaminated the water directly by spills during measurements and cleansing of the spray equipment in water sources. This is related to the low number of farmers who received pesticide extension services in respect to the high rate of pesticide use in the area (Table 18), and inadequate agricultural extension officers. It means, majority of the vegetable farmers in the study area apply pesticides with inadequate knowledge, hence improper application and handling practices used and may leads to excessive or inadequate quantities which may increase accumulation of residues in ecosystem components like water and food chains to toxic levels, or cause pest resistance to pesticides which provoke farmers to spray excessively, inputting more pesticide residues to the environment.
Majority of farmers used a lot of pesticides in their fields (Table 10), even when they knew that through runoffs pesticides easily reach water sources. This implies that something forced them to continuously use pesticide, perhaps monetary attachment or profit gains for livelihood. Since more than 80% of the farmers reported their vegetable gardens being located on the hill sides of the water sources and others had their vegetable fields located in the valleys where water sources were found; and 100% of them reported that water collecting sources were all located in the valleys, imply a high risk of contaminating water sources by pesticides from vegetable fields through runoffs, percolation through soil particles and spray drifts brought down by rain, hence increasing pesticide residue in water
Farmers used arbitrary tank-mixtures of pesticides as a way to increase effectiveness or save on labour. A similar situation was reported from Tanzania where a study on pesticides usage in small-scale vegetable farms revealed that a third of the interviewed farmers applied pesticides in tank-mixtures (Ngowi et al., 2007; Jokha (2015). In all cases, there were no specific instructions either from the labels or extension workers regarding these tank mixtures. Mixing of pesticides by inexperienced farmers is not encouraged because the combinations used are indiscriminate. The practice defies some of the basic principles of pesticide management. For instance, Metcalfe et al., (2014) in his recommendation of strategies for pesticide management, states that the use of mixtures of pesticides must be avoided, since mixtures of pesticides generally result in the simultaneous development of resistance.
Binhney (2001) working in Ghana attributed the increase in incidences of insect pest infestation of tomato after pesticide applications to indiscriminate combinations of pesticides, particularly of insecticides. Moreover, label instructions do not cover tank mixtures of pesticides and give no information on the compatibility of inert ingredients such as emulsifiers and wetting agents. It is riskier to mix two different types of formulations for example wettable powders with emulsifiable concentrates.
Smit et al., (2002); Karungi et al., (2011), Nansen (2013) and Jokha (2015) observed that there was an interaction between fungicides, insecticides and water mineral content that influenced the efficacy of individual pesticide against fungal pathogens and insect mortality and some tank mixtures induced phytotoxicity on tomato. There is limited information on the reaction and effects of the mixtures being used in the case studies. In addition, farmers did not consider that unspecified tank mixing of pesticides could be less effective and cause adverse effects to their health or the environment. Instead, the tank mixing was carried out to save time, labour cost and with anticipation of high efficacy in pests and diseases control. Sherwood et al., (2005) also reported that potato farmers in Ecuador were mixing pesticides mainly to reduce costs associated with spraying.
Findings in this study were also in agreement with findings from the case studies elsewhere in Sub Saharan Africa (Matthews et al., 2003; Ntow et al., 2006; Jokha 2015; Ngowi et al., 2007; Karungi et al., 2011) which show that internationally banned/restricted pesticides such as Carbofuran and Endosulfan are still being used by minimally educated farmers on horticultural crops. These pesticides pose a serious threat to the ecosystem. The problem is particularly widespread in sub-Saharan Africa, where the advent of liberalization of pesticides input markets has weakened quality control (FAO/WHO, 2001; Jokha 2015). Prior to liberalization, there were relatively few actors involved in pesticide provision, which made regulation and control simple.
In Uganda, importation and distribution of pesticides and other agricultural inputs used to be conducted by the Government and its Parastatals, which had proper procedures for safe handling and distribution of pesticides. Entry of more firms into the market runs the risk of erosion of quality control and packaging standards, the breaching of national regulations and the unimpeded movement of banned or restricted chemicals across borders (Mudimu et al., 1995; Jokha 2015). It also raises concerns about the ability of regulatory agencies to control their activities, since it requires more vigorous scrutiny and screening of imports and monitoring of distribution and usage (Mudimu et al., 1995; Williamson, 2003; Jokha 2015) with huge financial and human resource implications for these agencies.
Pesticide provision in a market-driven economy needs an effective regulatory framework in order to create full and fair competition, to protect the environment such as aquatic resources, to guarantee the quality of the products and to avoid the spread of pests and diseases (Shepherd and Farolfi, 1999; Jokha 2015). These are critical challenges for hard-pressed African regulators.
Most of the pesticides on the Ugandan market in particular are pesticides that have been around for a long time within a limited range. On record in 1999, 190 pesticide formulations had been registered (includes insecticide, fungicides, and herbicides), a pittance if compared to developed countries like the United States of America; where over 50,000 had been registered by that period (Schaefers et al., 1999; Jokha 2015). This is a great disadvantage to pesticide users who have limited choice for safe pesticides. This discrepancy in accessibility to safer pesticides between countries at different levels of economic development poses a challenge in developing safer alternatives such as IPM systems in some developing countries. Safer pesticides are either inaccessible or outside the income bracket of small-scale farmers. For such countries to remain competitive in international export markets, the policy environment, particularly regarding registration of newer and safer agrochemicals must be more conducive.
The improper disposal methods of the empty pesticide containers and plastic bags of pesticides imply poor handling. The containers and plastic bags being either thrown in the pit latrines, thrown away in the bush or in water bodies, left around the farms or open burned. This observation correlates with a study in Brazil which assess exposure to pesticides in which most respondents above 50% reported to leave empty pesticide containers within their fields (Araujo et al., 1999; Jokha 2015).
Most pesticides have been classified as insecticides, acaricides, molluscides, nematicides, fungicides, rodenticides and herbicides. The common types include organophosphates (Bromophos, DDVP (Dichloro dimethyl vinyl phosphate), Diazinon, Dursban, Dimethoate, Malathion, Parathion), organochlorines (Aldrin, DDT (Dichloro diphenyl trichloroethane), Dieldrin, Lindane, Thiodan, Toxaphene), carbamates (Dithane M45, Dithane M22, Furadan), pyrethrins/pyrethroids (Ambush CY (Permethrin), Ripcord (Cypermethrin, Decamethrin), phenoxy acetic acid (2-4-D (Dichlorophenoxy acetic acid), 2-4-5-T (Trichlorophenoxy acetic acid), MCPA (Monochlorophenoxy acetic acid), inorganic metals (shell copper (copper oxide), lead arsenate arsenic trioxide, phenylmercuric acetate) and bipyridyls (Grammoxone (Paraquat), Weedol and Diquat).
Vegetable farmers use a variety of these pesticides to control a host of pests, ranging from pre-harvest termites to post-harvest storage pests. While many are contact pesticides, systemic pesticides, which are potentially riskier because they penetrate living tissue, are also used.
According to Jeyaratnam (1990) and Zare (2015), 80% of the Uganda’s population are involved in agriculture and a modest estimate of 3% of all agricultural workers in developing countries are affected by pesticide poisoning each year translating into over 700 000 cases in Uganda annually. Safety behaviors in pesticide use are considered the most important determinants of the adverse health effects among farmers, which meant that the risk of pesticide exposure was strongly associated with farmer’s behavior when working with pesticides (Sharifzadeh et al., 2019). However, there is limited understanding of farmer’s behavior and its determinants especially in developing countries like Uganda. The sampled farmers used different types of insecticides, and fungicides. Some of the farmers applied weedicides for field preparation for vegetables. Both insecticides and fungicides were used by all the farmers since insect and fungal attack was severe.