The Use of Herbicides in Agricultural Practices in Mubi Region

Farmers all over the world are waging war against insects and weeds as they struggle to produce bountiful crops to meet increasing demand. The most effective weapon to fight this war is by the use of herbicides. In spite of the benefits of using herbicides, research has shown that their use can have negative impact on human health and the environment. A rapid appraisal via questionnaire administration and persona! contact with key stakeholders (users of herbicides and suppliers) and literature search were the main instruments employed for this work. Out of 152 questionnaires received 76 per cent affirmed that they use herbicides on their farms. None of the respondents was aware of any future consequences of herbicide exposure on health. It was gathered during the study that the main reason for using herbicides is to control weeds. Herbicides frequently used in the region are the ones that contain active chemicals such as, Paraquat dichlorin, Glyphosate and Atrazine. Poor handling of herbicides has increased the risk of contamination in the environment thereby posing serious health hazard. As a result of the increased use of herbicides in the region, more studies need to be conducted to ascertain the levels of contamination of toxic chemicals (dioxin) in water and soils of the region. Introduction Herbicides are chemicals that kill or inhibit the growth of unwanted vegetation such as weeds in crops or lawns. Herbicides can be classified into two (2) groups according to how they act and what they kill. They are selective and nonselective herbicides. Selective herbicides kill only certain types of plants, whereas nonselective herbicides kill all vegetation (Raven et al, 1998). They are mainly produced in order to check the problems of weed infestation faced by farmers as they cultivate their crops. These problems are responsible for crop losses, which affect the farmer's output. Weeds on the other hand, are pests that are undesirable competitors, parasites, or predators that affect the productivity or output expected from a harvest (Daniel and Edward, 1998). The major agricultural pests are insects, weeds, nematodes, bacterial and viral diseases, rodents and birds. Insects are not part of the major pests that attack crops; in fact, weeds are the major problem faced by farmers in terms of potential crop loss. There are about thirty thousand (30,000) species of weeds, and in a year a typical farm is infested with between ten to fifty (10-50) weed species (Daniel and Edward, 1998). Herbicides have the potential of reducing the amount of crop loss through competition with weeds. In spite of the benefits of herbicide application to farmers, its usage is not without problems. Research has shown that most herbicides contain dioxins, which have negative impact on human health and the environment. They can also affect the biodiversity of an ecosystem by killing non-target organisms. Several herbicides present clear risk to birds and are expected to be causing mortality on a frequent and routine basis (Muineau, 2002). Herbicides, do not only kill weeds but can also kill other organisms. Glyphosates which is a popular herbicide was discovered to be "extremely lethal" to amphibians (Chee, 2005). Organisms do not have to be killed to be negatively affected by herbicides. The stresses of carrying herbicides in their body make organisms more vulnerable to other diseases or stresses in their environment. (Raven et al, 1998). Some herbicides contain chemical compounds that are extremely toxic and persist in the environment. The persistent nature of some chemicals makes them to accumulate in the environment causing threat to humans and other organisms. The accumulation of these chemicals for long period makes them enter the food web and are also known to affect other organisms for which they are not intended (Charles, 2005). Herbicide Drift as an Environmental Problem Herbicides do not stay where they are applied, but tend to move through the soil, water and air, sometime long distances. Mobility of herbicides and other pesticides in the environment is also a problem for humans. .All herbicides can drift as spray droplets, but some herbicides are sufficiently volatile to cause plant injury from drift of vapour (fumes) (Ndsu, 1993). Drift can contaminate drinking water as it moves into rivers and other water sources. Fishes for example, can be affected by herbicides that were applied to agricultural lands Kilometers away and that are washed into rivers and streams by rain. When the concentration of herbicides is high in water it may kill fishes and if the concentration is low the fishes may suffer undesirable effects such as bone degeneration (Raven et al, 1998). The contamination of water ways by herbicides can damage the balance of the aquatic ecosystem. Implications of Exposure to Herbicides Herbicide applicators and farm workers bear the brunt of acute and chronic exposures, especially in developing world. The number of people harmed continues to rise, despite efforts to curtail acute exposures (Murray and Taylor, 2000). Exposure to herbicides can damage human health. Pesticide poisoning caused by short-term exposure to high levels of herbicides can result in harm to organs and even death. Long-term exposures to lower levels of herbicides can cause cancer and also disrupt the human endocrine (hormone) system (Raven et al, 1998; Charles, 2005). A person with rrrild case of pesticide poisoning may exhibit symptoms such as nausea, vomiting and headaches. The cases of acute poisoning have risen from about five hundred thousand (500,000) per year in 1972 to ari~ estimated" twenty five million (25,000,000) in the early 1990s (Levine and Doull, 1992). This figure is still rising in the developing world. In a research conducted in India by Gupta (2000), it is shown that "fifty one per cent (51%) of food commodities are contaminated with pesticide residues and out of these, twenty per cent (20%) have herbicide residues above the maximum residue level acceptable by world standards. Many health and environmental costs of intensive pesticide use have become starkly apparent. Therefore, care is needed in the use of herbicides in order not to accept the short-term gain at the expense of our health and damage to environment (Eddleston et at, 2002). The use of herbicides is rising in most developing countries and this is bound to create negative impact on the environment and health of the people. Therefore, this study assesses the use of herbicides in agricultural practices in Mubi region. The study is hoped to be useful to ecologist, health workers, and users of herbicides and will also generate interest for further studies on the effects of herbicides on the health of humans and the environment. The Study Area Mubi region lies between latitude 9°30 and 11° 00' north of the equator and longitude 13°00 and 13° 45 east of the Greenwich meridian. It has a land area of 4,728.77 Km and a population of 759,045 in 2003 (Adebayo, 2004). The region consists of five (5) local government areas namely: Madagali, Maiha, Michika, Mubi-North and Mubi-South (Fig. 1). These local government areas form the Adamawa north senatorial'district. It is geologically located within the North Eastern Basement complex of Nigeria and belongs to the highland relief region of Adamawa State. Its elevation ranges from 400 metres to 1500 metres above sea level and it is mainly drained by River Yedzeram. The region has its lowest temperature in January (12.7°C) and its highest temperature in April (37 C). The mean annual rainfall ranges from 900mm to 1050mm. Methodology Two sets of questionnaires were administered to farmers and dealers of herbicides in Mubi. One hundred and fifty two (152) questionnaires were administered to farmers and twenty (20) to the dealers of herbicides in Mubi Town. The dealers were selected based on their experience of not less than four (4) years in the business of selling herbicides. Simple statistical methods were adopted in analyzing the data collected. The secondary data were collected from both published and unpublished materials. Results and Discussion The Use of Herbicide by Farmers The questionnaires collected from farmers revealed that majority (76%) of the respondents use herbicides on their farm. Table I shows the percentage of respondents that use herbicides on their farms. Table 1: Use of Herbicides by Respondents Response __________ Number of response __________ Percentage ___________________ Yes 11.6 76 No 36 ______ 24 _________________________