A Professor of Chemical Weed Control and Plant Protection, Rex Aladesanwa, has raised the alarm over the widespread usage of banned chemicals for pest control by farmers and other users across the country. This was part of his submission while delivering the 169th inaugural lecture of the Federal University of Technology, Akure, FUTA on Tuesday, July 9th, 2024. Aladesanwa listed some of the banned chemicals, which are available in the open market and sold by pesticide dealers and used by farmers across Nigeria, to include paraquat, parathion, and methyl parathion. He called on government to ensure that all the banned chemicals listed in the eleventh schedule of the policy guidelines for pest control of the Federal Ministry of Environment are removed from circulation.
Aladesanwa, a professionally trained weed scientist and plant protectionist, whose research activities published in international journals include evaluation of herbicides residue, chemical weed control, cultural weed control and integrated pest management, recommended that to mitigate the hazards concomitant with the marketing and storage of pesticides, only licensed dealers should be permitted to store and sell them. He added that pesticides must not be stored together with food. He Advised that they must be stored in only lockable cupboards and should be sold only to adults with packaging and labelling complying with regulations, which when violated should lead to the dealer’s license being withdrawn.
The lecturer said a major way to control the ravaging global food crises, especially as it affects Nigeria is to responsibly apply chemical herbicides and pesticides to farming activities. Professor Aladesanwa who titled his lecture, “Tackling the Scourge of Weeds: The Use and Challenge of Herbicides (Weedkillers)” said “The impact of the presence of weeds on crop production is very considerable. Estimates suggest that weeds are responsible for an overall reduction of somewhat more than 10% in the yield of the major world crops, accounting for a huge annual loss of food supplies. Weed deprive the crop water, mineral nutrients, and light, and so prevent it from achieving potential.”
Citing a report by the Food and Agriculture Organisation (FAO), he said “While in developed countries weed management is done through the use of herbicides and machinery, in poorly developed or developing countries, particularly at the small farm level, the farmer and his/her family spend more than 40 percent of their labour time in hand-weeding operations. This situation limits the productivity of the farmers and the socio-economic development of their family.” Aladesanwa summed it up saying “to minimize the direct impact of weeds on crops and achieve optimum crop yields requires the most efficient methods of management.”
Classifying herbicides as organic and inorganic, the don said “Based on time of application, herbicides are classified into pre-plant, pre-emergence, and post-emergence treatments. A pre-plant herbicide is applied before the crop is planted. Some herbicides are very volatile and have to be applied and incorporated into the soil before the crop is planted. Herbicides in this group are called pre-plant soil incorporated herbicides. A pre-emergence treatment is any treatment made prior to emergence of a specified weed or crop while a post-emergence treatment is any treatment made after the drop or weeds must have emerged.”
Dwelling on methods of weed control, the don said major components of weed management are preventive, cultural, biological, and chemical, including Integrated Weed Management (IWM) which he referred to as weed management strategies rather than a control or a management system.
The don further recommended that when selecting the pesticide (active ingredient), an active ingredient which is selective vis-à-vis the main pest should be used. He said the active ingredient of the pesticide must be changed to prevent the development of resistance where the control measure needs to be repeated, adding that preference should be given to an active ingredient of lower toxicity and lowest possible persistence in soil and water over one of higher toxicity, while the necessary preharvest interval must be observed to prevent the accumulation of toxic residues on food crops.
Professor Aladesanwa counselled farmers against the repeated use of the same herbicide over a prolonged period to prevent high weed infestations that are tolerant of the herbicide in order to preclude herbicide resistance in the longer term.
He further called on the removal of enforcement of standards and regulations regarding public health pest control from the jurisdiction of the National Agency for Food and Drug Administration and Control (NAFDAC) and put under the regulatory authority of the National Environmental Standards and Regulations Enforcement Agency (NESREA), a parastatal of the Federal Ministry of Environment, which will ensure that pesticides including herbicides, and their quality, packaging, and must, as a minimum requirement, comply with the standards laid down in the FAO’s code of conduct on the distribution and use of pesticides.
In her capacity as the Chair at the event, the Vice Chancellor, Professor Adenike Oladiji, described the lecturer as an erudite professor who has added value to knowledge and research in his field of study. She said his teaching and research endeavors which span over 30 years has churned out great scholars blazing the trail across the globe. She said the lecture highlighted the beneficial potentials and limitations of the use of herbicides to control weeds and how to improve food production to combat hunger.
