‘Exploding’ use of 2,4-D in Africa


I was recently in southern Ethiopia conducting an evaluation of pesticide use in USAID-funded Farmer to Farmer programs managed by the Catholic Relief Services. As part of the evaluation, I was tasked with familiarizing myself with the list of pesticides approved for use in Ethiopia. One pesticide stood out; 2,4-D.

To many people, 2,4-D is just a herbicide that performs wonders against unwanted dicotyledonous plants that are an eyesore on otherwise plush lawns. The compound is known as 2,4-dichlorophenoxy acetic acid. Originally developed during World War II for the purpose of increasing crop yield by suppressing weeds, 2,4-D was later introduced commercially in 1946 and soon became the most widely used herbicide globally. In fact, 2,4-D was the first ‘selective’ herbicide that eliminated dicotyledonous plants such as dandelions and pigweeds without harming monocotyledonous crops, such as maize, wheat, rice, barley, and teff. When 2,4-D is applied on a susceptible plant, it causes the plant to grow uncontrollably which results in the destruction of vital plant tissues leading to death. The effect of 2,4-D on a plant is considered to be like a cancer.

Having the distinction of being the first commercially available herbicide, 2,4-D is still widely used in agriculture as well as home and garden sectors. In the US, 2,4-D-tolerant crops have been introduced due to the belief that glyphosate-tolerant crops are reaching the end of their life cycle due to the proliferation and abundance of glyphosate-resistant weeds. With increased use of 2,4-D expected, the likelihood of more 2,4-D-resistant weed species developing may lead to the possibility of this herbicide having a similar fate as glyphosate and become obsolete in future.


Field of teff  in southern Ethiopia.

In southern Ethiopia, farmers have become highly dependent on 2,4-D to keep their cereal crops free of dicotyledonous weeds. The level of exposure to 2,4-D is presumably high but the impacts on human and environmental health are unknown since no follow-ups are made after the herbicide has been sold. Nonetheless, the following observations were made during my evaluation:

  • Disappearing honeybee populations – which may be attributed to 2,4-D applications that eliminate plants that would otherwise serve as nectar sources for honeybees.
  • The herbicide is no longer working – which may indicate there is some tolerance or resistance to 2,4-D or perhaps the applications were made erroneously due to a number of reasons that may include calibration, application timing, etc. Another reason could be the quality of the 2,4-D being applied.

Of most importance, however, was the fact that most Ethiopian farmers tended NOT to use personal protective equipment (PPE) when they applied 2,4-D because they felt that the herbicide was ‘safe’ and PPE was unnecessary. But is it?

We know that 2,4-D can:

  • irritate the eyes and skin upon exposure,
  • induce coughing, cause dizziness and temporary loss of muscle coordination when inhaled for a prolonged period, and
  • impede the normal action of estrogen, androgen, and thyroid hormones, and is classified as an endocrine disrupting hormone.

At this point you may be wondering if there are known chronic effects of 2,4-D. Researchers have observed apparent links between 2,4-D exposure and non-Hodgkin’s lymphoma (a blood cancer) and sarcoma (a soft-tissue cancer) (Ibrahim et al., 1991). The link is not very strong and requires further study. However, in 2015, the International Agency for Research on Cancer declared 2,4-D a possible human carcinogen based on evidence that it damages human cells and causes cancer in laboratory animals in a number of studies (

There is no question that the current usage of 2,4-D in Ethiopia and elsewhere in Africa raises concern. Whenever 2,4-D is sprayed there is a high likelihood that the herbicide spray will drift, partly because the chemical is volatile, and affect unintended targets. The first line of defense is to increase the pesticide knowledge in communities where 2,4-D is used widely. Then, at minimum, adequate access to and availability of PPE must be ensured.

Ibrahim, M. A., G. G. Bond, T. A. Burke, P. Cole, F. N. Dost, P. E. Enterline, M. Gough, R. S. Greenberg, W. E. Halperin, E. McConnell, I. C. Munro, J. A. Swenberg, S. H. Zahm, and J. D. Graham. 1991. Weight of the evidence on the human carcinogenicity of 2,4-D. Environ Health Perspect 96: 213–222.
SUPESTA ( confronts the challenge of pesticide use in Africa. We:
  • work with smallholder farmers, agro-dealers, extension personnel and others who routinely apply pesticide and help them build a knowledge base in pesticide use and safety,
  • promote alternative approaches to total reliance on pesticides, such as integrated pest management, and
  • help develop easily accessible tools that provide information on pesticide handling.
  • Ultimately, less harm will come to humans and the environment when pesticides are used by knowledgeable people. 

DDT – The ‘Poster Child’ of Pesticide Safety


One pesticide that most people can name is DDT. In fact, DDT is so common to the point that it often features in crossword puzzles in newspapers and magazines with clues like ‘banned insecticide’ or ‘banned pesticide’. So, it is probably safe to assume that many people know that DDT is banned. However, would they know why DDT was banned or whether it is still being used today despite its banning?

Dichloro-diphenyl-trichloroethane (DDT) is an organochlorine insecticide that was first synthesized in 1874 and later became widely used for insect control in the 1940s. DDT became a popular insecticide in the United States and was used widely in agriculture and generally around people. In 1962, Rachel Carson wrote a book titled ‘Silver Spring’ that brought to light the devastating effect that DDT had on the environment. One of the detrimental effects pointed out by Carson was how DDT contamination was responsible for the near-extinction of the bald eagle, the national symbol of the United States of America. Thereafter, the United States Environmental Protection Agency (USEPA) was established in 1970 and DDT was banned in 1972.

DDT was one of the most widely used pesticides following World War II and was promoted as having insect-killing powers that would make homes healthier and comfortable. At the same time, evidence was mounting on how DDT could persist in the environment and bioaccumulate as it moved up the food chain. Bioaccumulation occurs when an organism absorbs a substance, such as a chemical or pesticide, at a faster rate than it can metabolize or excrete it. The substance can then become highly concentrated in an organism and cause problems.

Thus, because of DDT bioaccumulation, the compound became particularly deleterious to birds by making the shells of fertilized eggs so brittle that they cracked under their parents’ weight. The most threatened birds included peregrine falcons, ospreys, brown pelicans, and bald eagles, all of which were brought to the brink of extinction.

By the time DDT was banned in the US it had already contaminated nearly everything that Americans ate. Several years thereafter, DDT and its carcinogenic metabolite dichloro-diphenydichloro-ethylene (DDE), were still being detected in US food.

The story of DDT does not end with its banning by the USEPA. Elsewhere it is still in use in countries that continuously battle malaria until suitable alternatives for the control of mosquitoes can be found. How those countries are being affected by the continued use of DDT is largely unknown because there seemingly are no ‘Rachel Carsons’ to study the effects on the environment so as to alert society. I doubt that many know the reasons why DDT was banned in the first place and use it because it is moderately toxic and relatively safe when handled.

When growing up in Kenya, I applied DDT by hand to control corn borers without using personal protective equipment. It never even crossed my mind that there was any problem with the chemical and it is only later when I had the opportunity to study pest management that I learned the reality. I wonder how many Africans are even remotely aware of the dangers posed by the continuous use of DDT?

SUPESTA ( confronts the challenge of pesticide use in Africa. We:
  • work with smallholder farmers, agro-dealers, extension personnel and others who routinely apply pesticide and help them build a knowledge base in pesticide use and safety,
  • promote alternative approaches to total reliance on pesticides, such as integrated pest management, and
  • help develop easily accessible tools that provide information on pesticide handling.
    Ultimately, less harm will come to humans and the environment when pesticides are used by knowledgeable people. 

The good, bad, and ugly about pesticides

So far in my blogposts I have talked about pesticides as one entity. However, to get to the heart of why pesticides deserve more attention than what they currently receive, one must delve deep and look at aspects of individual pesticides to understand why they are good and also in what circumstances they can become bad, or even ugly.

This month, February 2018, is the inaugural annual National Pesticide Safety and Education month. Under the sponsorship of the National Science Foundation Center for Integrated Pest Management, this initiative is dedicated to reinforcing core principals of safe pesticide use across the United States to raise awareness of the potential hazards of pesticides and to support Pesticide Safety Education Programs (PSEPs) conducted by land-grant universities. In addition to pesticide stewardship efforts by all stakeholders, PSEPs are important because they help keep users informed by staying current with changes in pests and pesticides. Clearly, Africa must create similar PSEPs as pesticide use escalates and knowledge lags behind.

Spraying herbicide

A farmer spraying herbicide on his crop. Only a portion gets to the intended target with the remainder reaches where not intended and can cause serious harm.  Picture courtesy of

Many an African farmer makes the decision to use a pesticide because he/she believes that only good things happen when you use a pesticide. That is not an informed choice and one that is likely to lead to bad or ugly things happening. So, as a service to Africans, let’s begin to talk about selected pesticides which are commonly used and why they are good, bad, and sometimes ugly.

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Introducing Pesticides to Smallholder African Agriculture

Managing crop pests has always been a major part of my life. Ever since I was able to handle a hoe and use it for land preparation and weeding, I became a member of our family’s crop management team. Ultimately, hoeing became part of my life because we grew sizeable acreage of maize (corn) and edible beans which we used as staple foods.

Besides hoeing, cultivating maize often required an application of insecticide to prevent stem borers from establishing, damaging the crop, and reducing yield. The insecticide was administered by placing a small amount of a granular formulation into the funnel of each maize plant before tassels emerged. We used no personal protective equipment (PPE) because we knew no better and were given no advice to the contrary. Despite some yield-reducing pest problems occurring in the bean crop, no pesticides were applied in-season.

The next battle with pests came after crops were harvested and stored. The major storage pest at the time was a grain weevil that would infest maize and bean seeds in storage and, to a large extent, render the produce inedible. Consequently, insecticides were mixed with the harvested maize and beans by hand, without PPE, prior to bagging and storing (see Oct. 9, 2017 blogpost). Of particular note here is that once pesticides were applied in storage they could not be removed from stored maize or beans prior to consumption.

Much of what I experienced with pesticide use in Kenya in the 1970s and 1980s is still going on today, especially among rural smallholder farm families. The only difference is that these rural communities now have access to a wider arsenal of pesticides to choose from for their pest management needs. Whereas this might be seen as advantageous to the farmer, we should be concerned that basic pesticide knowledge and understanding is lacking.

What kind of basic knowledge should smallholder African farmers have to handle and apply pesticides?
I became aware of the benefits and hazards of pesticides when I pursued an educational path and career in crop protection. With the knowledge I acquired, I conducted research with pesticides and also taught university courses where I introduced students to the various facets of pesticide use. Presently I have directed my focus to confronting the challenge of pesticide use in Africa. Stepping up to this challenge means that I must strive to ensure relevant information is provided to smallholder African farmers.

Perhaps the starting point is in highlighting pesticides that were/are widely used and have been banned or are problematic.

Tune in for my next series of blogposts as I explore the various facets of pesticides – the good, the bad, and the ugly.

For more information about confronting the challenge of pesticide use in Africa, please visit:

My Grandmother’s Medicinal Plants and Pesticide Use

Guku Besi 2

Debra Besi Ogada, my grandmother in 1976

In this blogpost, the spotlight is on my late grandmother, Debra Besi Ogada, and the importance of her work as a herbalist (traditional healer) within her rural community in western Kenya. My grandmother grew up in an era when the only medical treatment available was from a herbalist or traditional healer who was valued for knowledge of plants with medicinal properties. Such knowledge included an understanding of the biology and ecology of the plants, when they were to be harvested and used, and the dosage to prescribe for treatment of an ailment.

According to the World Health Organization (WHO), 80% of the population in Africa use traditional medicines for their primary healthcare needs. Of all traditional medicines, about 85% of them are made using plant extracts. Furthermore, WHO estimates that in Sub-Saharan Africa, there is one traditional healer per 500 people whereas there is one medical doctor per 40,000 people. The importance of medicinal plants cannot be overemphasized, and they must be protected for the benefit of Africans. In addition, medicinal plants are a resource for medicine, since most of these plants have not been fully characterized and may have untapped medicinal potential. Medicinal plants are often rare, possibly threatened or endangered, and if herbicides are used without sufficient oversight, as is common in Africa today, the probability of causing local or widespread extinction of the medicinal plants is relatively high. Possible extinction of the medicinal plants is a huge threat to the livelihood of most rural African communities where modern medical facilities are not easily accessible.

A few years ago, as a weed science faculty member at North Dakota State University, I was given the responsibility of developing a case for the use of a herbicide that was not registered for use in potato. Referred to as an Environmental Protection Agency (EPA) Section 18 exemption, permission is sometimes needed when there is an emergency situation that requires a remedy and available options are few. In this particular case, the herbicide was on the path to full registration but had not been cleared by the US EPA. To obtain the special exemption from the EPA, I had to provide assurances that some of the threatened orchid species in North Dakota would not be affected when the herbicide was applied. This I did, and the special exemption was granted for that particular growing season. In Africa, this level of regulation is not available and once a herbicide is available on the market it can be used at the discretion of the buyer.

Towards the end of her life, my grandmother moved from her rural home to live with us in the city because she needed more care. Her absence was an inconvenience to many within her community because they were forced to look for alternative healers or otherwise travel the lengthy distance to see my grandmother and receive treatment. To me, however, having my grandmother living with us was my introduction to a knowledge base that would lead to my career in weed ecology and biology. As a herbalist, my grandmother needed to secure rare plants for her herbal remedies. As she grew older, she often relied on others, myself included, to get the required plants after she had instructed me where to locate them.

Part of my desire to become a weed scientist was to one day follow in my grandmother’s footsteps albeit with a difference. My hope was that I would study the plants that she used in her herbal remedies before the knowledge was lost or plants became extinct. The likelihood of extinction is accelerated by the adoption of herbicides and their widespread use. Improving the knowledge of rural communities to help improve their appreciation of medicinal plants, coupled with a better understanding of pesticide use can help protect these plants for present and future generations. Perhaps too, it will be a step in helping regulators ‘catch up’ and get a handle on ensuring sustainable pesticide use that not only protects humans and the environment, but which also helps preserve medicinal plants, some of which are rare, threatened, or endangered species.

Fansworth, N. R. and D. D. Soerjarto. 1985. Potential consequences of plant extinction in the US and the current and future availability of prescription drugs. Economic Botany 39(3): 231-240.

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