Impacts of Pesticides Use and Its Influence on Pest Management

Land Cover and the Need for Introduction of MTS

The total Agricultural land area of Ghana as at 2012 stood at 14,038,224 hectares, out of which 7,847,300 hectares is under cultivation (MOFA/SRID, 2013). The population of the country keeps increasing at an alarming rate of 2.2% as at 2012, with its attendant increased mouths to feed. In order to continue cultivating and increasing yield, farmers are faced with the task of using various pesticides to control weeds, pests and diseases.

The rate of deforestation in Ghana is estimated to be one of the highest in the world after Togo and Nigeria. At an estimated annual rate of 2%, equivalent to 135,000 hectares per annum (ENA Ghana, 2017). This has been brought about by increasing population and the resulting growth in the demand for food, for other agricultural products, for energy (fuel wood and charcoal) and other forest products FAO. This is exacerbated by unsustainable harvesting practices for timber and other forest products.

Historical Perspectives Forest Restoration in Ghana

Since 1946, there has been several attempts at increasing the stocks of high value timber species in Ghana’s forests.

According to Nolan & Ghartey, 1992, in order to improve the stocking of the Wet Evergreen forest reserves (which were in their view poorly stocked) and sustain the supply of the then ‘desirable’ species such as Khaya, Entandrophragma, Lovoa and Heritiera, the enrichment planting strategy was adopted. The program was however abandoned after planting an area of about 2,500 ha, due to lack of budgetary support.

After many other similar attempts were made at restoring most degraded forest reserves or protecting and increasing the forest cover of Ghana had yielded no significant results, the government of Ghana in September 2001 launched the National Forest Plantation Development Program (NFPDP) to accelerate the rate of establishment of forest plantations in the country. The program according to FC, 2016, had among others, three key objectives: restoring the forest cover of degraded forest lands; generating employment as a means to reducing rural poverty; addressing the future wood deficit situation and enhancing food production through the adoption of the Modified Taungya System.

Deforestation and forest degradation in Ghana

Agricultural pesticides are powerful substances that are developed, produced and used to mitigate crop damage or loss by pest organisms. Increasing yields in agriculture and checking insect-borne diseases (malaria, dengue, encephalitis, filariasis, etc.) in the human health sector are significantly enhanced by controlling pests and diseases.

The decimation of beneficial agricultural predators of pests has led to the proliferation of several pests and diseases. Despite all these impacts and costs, farmers continue to use pesticides in most countries at an increasing rate, while biological methods of pest control have become limited.

Continuous use of pesticides has resulted in damage to the environment, caused human ill health, negatively impacted on agricultural production and reduced agricultural sustainability.

In Ghana, an extensive forest estate, consisting of 1.6 million hectares of forest reserves, was gazetted in the High Forest Zone (HFZ) in the 1920’s. At the time there were large areas of forests outside these gazetted forest reserves across the country. Over the period significant portions of these forests have been lost or degraded. The key underlying causes of deforestation and forest degradation include population and economic growth and weak governance structures. High population and economic growth have led to high domestic wood consumption and high demand for timber to satisfy export markets.

Additionally, growing domestic and export demand for agricultural commodities such as cocoa, oil palm, cashew, and food crops has led to large scale conversion of forests to agricultural uses.

The government of Ghana, through the Forestry Commission, came up with an approach to rejuvenating old degraded forests that took into account financial benefits for farmers and other stakeholders involved and transferred ownership of the trees from a single entity (the government) to multiple owners (farmers, local communities, government and land-owners). MTS is an approach to the allocation of economic benefits and resources. Farmers were therefore allocated a portion of degraded forest land to cultivate food crops while at the same time planting and tending to forest trees until the tree canopy closes after 3 years, then they are moved to other plots. With food crop cultivation came the need to control weeds, diseases and pests which necessitated the introduction of pesticides by the farmers.

The Modified Taungya System

Taungya was developed in Burma as a result of numerous confrontations between farmers and the British forestry service, and was used primarily to allow the Karen much needed access to reserve forest land (Bryant 1994), and was introduced in Ghana as early as 1928 when the then Forestry Department was charged with the responsibility of establishing forest plantations for the production of wood in the long term and also to meet the needs of farmers for fertile land in areas where farm land outside the national permanent forest estate was infertile and limited. There was an intensification of taungya plantation establishment in Ghana between 1969 and 1985 (FD, 1985) as part of the Operation Feed Yourself Program. It was however not widely adopted despite the supposed advantages, and virtually came to a halt due to the problem of co-partnership since farmers had no right in the benefit sharing.

The Ghanaian government, within its 1994 Forest and Wildlife Policy (FWP) and forest plantations development program, reviewed and reintroduced the traditional Taungya system in 2002 as the Modified Taungya System (MTS).

Taungya starts as an agroforestry system during the initial three years, and then evolves to a plantation system when the trees form a closed canopy, and farmers are expected to tend the trees to maturity. Farmers are also expected after three years to move to other plots, mostly degraded state-owned/managed forest reserves, to repeat the agroforestry practice. Interactions between crops and trees under taungya systems are designed to achieve complementary rather than competitive effects.

The farmers were permitted to cultivate their food crops which were interplanted with the forest trees on the same piece of land. The farmers, in addition to the food crops they harvested, have a 40% share in the Standing Tree Value (STV) of the planted trees. The Government has a 40% share while the landowner and community will have a 15% and 5% share respectively (GFPS, 2016).

The FC provided technical direction, surveyed and demarcated degraded forest reserve lands and supplied pegs and seedlings while the farmers provided all the labor inputs in the form of site preparation, pegging, planting, tending and fire protection. Tree planting was strictly monitored, but no restriction was made on the types, dosages and forms of pesticides which can and cannot be used by the farmers in achieving their crop production goals as long as the trees are being ‘protected’ form them.

Pesticides and the need for them

In order to reduce time, energy, resources and funds spent in manual land preparation, weed, and disease and pests control, MTS farmers turned to the use of pesticides for their crop production activities.

Pesticides are widely used in most sectors of the agricultural production to prevent or reduce losses by pests and thus can improve yield as well as quality of the produce, even in terms of cosmetic appeal, which is often important to consumers.

The term pesticide includes a broad range of compounds including insecticides, fungicides, herbicides, rodenticides, nematicides, plant growth regulators and others.

In many countries, achieving food security is a primary concern in agriculture. Sustainable intensification of production and prevention of post-harvest losses are key elements.

In this regard, there is a need for sustainable responses to outbreaks of endemic and trans-boundary pests and diseases that are affecting agricultural production and food security. With growing global trade in agricultural commodities and produce, it is also important to ensure that transport of agricultural produce does not lead to the spread of pests and diseases.

While pesticides play an important role in plant protection, in many cases, misuse and other inappropriate use has actually exacerbated pest problems through destructive effects on natural control mechanisms and development of pesticide resistance.

To reduce yield losses, farmers frequently apply higher rates of pesticides than those recommended by experts and extension agents, usually as a result of the common belief that the application of high pesticide rates is more effective. In this context, however, decisions on pesticide applications are made without consideration of human health and environmental concerns by many farmers.

As an agriculture-based nation, the use of pesticides contributes much to the national development and public health programs. Since the introduction of pesticides in Ghana, its use to protect crops from pests has significantly reduced losses and improved the yield of crops such as cereals, vegetables, fruits and other crops. There has been a study growth of pesticide usage in Ghana, both in number of chemicals and quantities because of the expansion of area under cultivation for food, vegetables and cash crops.

Some farmers are of the view that the more or as often as they apply pesticides the greater the chances of higher yield and also destroying crop pest. They have no idea of the half-lives of these chemicals no the dangers they pose when misused.

Pesticide related issues have increasingly and extensively been highlighted in the media and have attracted sharp focus among industrialized and developing countries (FAO, 2005). It is estimated that, about one third of the world’s agricultural production is lost every year due to pests, despite pesticide use which totaled more than 2 million tons. According to the Food and Agriculture Organization (2005), more than 99% of world pesticide poisonings are reported in developing countries, although they accounted for 20% of worldwide pesticide use; due to easy access to more toxic products, less protection against exposure, limited knowledge to health risk and safe use of pesticides.

During the last decades, agricultural production has undergone immense growth, relying heavily on external inputs, such as pesticides and inorganic fertilizers, as means of increasing food production.

Brief History of Pesticides Application

Humans have utilized pesticides to protect their crops before 2000 BC. The first known pesticide was elemental sulphur dusting used in ancient Sumer about 4,500 years ago in ancient Mesopotamia. The Rig Veda which is about 5000 years old mentions the use of poisonous plants for pest control. By the 15th century, toxic chemicals such as arsenic, mercury and lead were being applied to crops to kill pests. In the 17th century, nicotine sulphate was extracted from tobacco leaves for use as an insecticide.

The 19th century saw the introduction of two more natural pesticides, pyrethrum which is derived from chrysanthermuons and rotenone which is derived from the roots of tropical vegetables (Miller, 2002).

Until the 1950s, arsenic based pesticides were dominant (Ritter, 2001). Organochlorines were replaced in the U.S. by organophosphates and carbamates by 1975. Herbicides became common in the 1960s led by atriazine and other nitrogen-based compounds carboxylic acids such as 2, 14 dichlorophenoxyacetic acids and glyphostate. Some sources consider the 1940s and 1950s to have been the start of the pesticides era. Pesticide use has increased 50-fold since 1950 and 2.3 million tons of industrial pesticides are now used each year. Seventy-five percent of all pesticides in the world are used in developed countries, but use in developing countries is increasing (Miller, 2004). In the 1960s, it was discovered that DDT was preventing many fish-eating birds from reproducing, which was a serious threat to biodiversity. Rachel Carson wrote the best-selling book Silent Spring about biological magnification of pesticides. According to Lobe (2006), even though the agricultural use of DDT is now banned under the Stockholm convention on persistent organic pollutants, it is still used in some developing nations to prevent malaria and other tropical diseases by spraying on interior walls to kill or repel mosquitoes.

Effects of Pesticides

Indeed, the use of pesticides boosted crop productivity and improved product quality, in terms of cosmetic appeal of fresh produce, but there are now concerns about overuse, mainly relating to contamination of water bodies, pesticide residues on food, and consequent negative effects both on wildlife and human health. The deleterious effects of these organochlorine pesticides on wild life primarily led to their ban from routine use in the US and many other countries in 1970’s and 1980’s (Dunlap, 1981). With the exception of endosulfan which was considered for restricted use in 2008, Ghana has banned the use of many organochlorine pesticides since 1985.

Fauna and flora have been adversely affected. Numerous short- and long-term human health effects have been recorded. Human deaths are not uncommon.

Pesticides are generally considered a remedy for farmers’ pest and weed concerns, farmers’ perceptions and use of the chemicals have not received much attention.

In Ghana, there has not been any known comprehensive study of the perceptions that drive pesticides use and its impacts in the Modified Taungya system of farming.

The perceptions of farmers regarding, in particular, pesticide risks to human health are important for a number of reasons: first, they may influence decisions regarding pesticide use; second, if these perceptions differ from expert opinion, it is useful to know why and whether they lead farmers to take more risks than they realize; third, they may influence the methods of protection used against pesticides; and, last, technical advice given to farmers on pesticide use and crop protection may be useless and irrelevant when it does not tally with their own perceptions of pesticide health effects.

Thus, knowledge of farmers' perceptions of pesticide effects may help in predicting their behavior regarding pest control.

Farmers' knowledge of the pros and cons of pesticides can be influenced by several socio-economic characteristics, but apart from socio-economic characteristics, farm characteristics are also related to the level of knowledge and ultimately reflect decision-making regarding pest control strategies and attitudes towards pesticide use. Farmers' awareness is often influenced by socioeconomic characteristics, such as formal education and level of technical knowledge regarding pesticide use. At the same time, decisions about pest control are quite subjective and may depend on several characteristics of farmers, including personal beliefs, perceptions, and preferences.