Agro Chemicals Crop Treatment


The use of chemicals for beans preservation has called attention of individuals, government agencies and organisations to food quality and safety in the country. Nigerians are worried that there might be a re-emergence of the killer-beans that claimed many lives and wiped off families in the 1990s, or the situation could lead to cumulative health burdens on Nigerians and the country.

From time immemorial, cereal farmers and grain merchants have often sought ways to preserve their products, beans inclusive, with the application of red dry peppers rather than pesticides.

When a recent video showing young two men using a synthetic chemical (Sniper) came to the public knowledge, the Consumer Protection Council (CPC) and the Nigerian Agricultural Quarantine Service (NAQS), among other regulatory bodies, came up with modalities to ensure that Nigerians consume wholesome beans. But the untold story is that the unofficial method of beans preservation is the use of these poisonous chemicals. Dry fish, maize and other pest-susceptible cereals and consumables are usually sprayed with these crop protection (not grain protection) chemicals.

A bean merchant who demanded anonymity said “what many people didn’t know is that farmers have always been using Sniper to preserve their grains. They don’t feel any remorse when applying it, because according to them, that is the only method they know for beans preservation.”

Bean weevils are common pests that attack beans. Cowpeas are highly susceptible to pest infestation, and this leads to huge post-harvest losses, lower food quality and poor food safety. To mitigate these losses, the majority of farmers and grain merchants employ various insect control measures, including the use of chemicals not minding the consequences of their actions.

Chemicals like organophosphates (such as DDVP), pyrethroids (such as Permethrin, Deltamethrin) and some already banned class of chemicals (organochlorides such as gammalin) for the storage of beans and this has led to food poisoning and death of consumers. Therefore, the general public is at risk due to their effects.

To correct the above the abnormal practice and ensure the safety of foods consumed by the Nigerians, the Ministry of Agriculture and Rural Development conveyed a stakeholders’ meeting in Abuja, bringing together the Nigerian Agricultural Quarantine Agency, the National Agency for Food, Drug Admistration and Control (NAFDAC) Standards Organisation of Nigeria (SON), the National Orientation Agency (NOA), and research institutes to find a lasting solution to the menace.

The Minister of Agriculture and Rural Development, Audu Ogbeh, while stressing the need to scale up campaign in ensuring Nigerians consume wholesome foods, noted that it would help prevent cases of liver and kidney problems.He said: “Why are so many people going down with liver, kidney and lung failures? Nobody knows exactly which particular misconduct of ours is leading to the damage of health of our people. Add all that, water that people are drinking in the communities is contaminated. Then, you can see why our life expectancy is so low.”

Ogbeh attributed the use of the chemicals to ignorance and poverty. He said rural women often use chemicals to ripen plantain or banana, adding that they also spread cassava products on the roadside, thus exposing foods to carbon deposits, dust and effluents.

The NAQS boss, Dr Vincent Isiegbe, pointed out that NAQS had been trying to engage people along the value chain so as to see how they could work together not only on beans, but also on other grains. He added that since 2017, it had partnered with the University of Ibadan and Ahmadu Bello University, Zaria to find a viable and sustainable bio-degradable agro-pesticide that farmers could apply.

The Executive Director of the Nigerian Stored Product Research Institute (NSPRI), Professor Olorunfemi Peters, further submitted that beans of safe moisture content can be stored with or without the use of chemicals. He explained that harvested and threshed beans could be stored for short and long term periods using the following procedures.

Farmers and marketers could preserve cereals with hermetic storage methods. This technology works on the principle of exclusion of oxygen gas from the storage environment. Hermetic storage facilities are air-tight structures which can be flexible or rigid and require no synthetic chemical application. For example, when using polythene lined jute bags developed by NSPRI, the bag should be filled to the brim with beans and properly tied or sealed.

Other flexible hermetic storage structures such as the Purdue Improved Crop Storage (PICS) bags developed by Purdue University, USA and ZeroFly Hermetic bags by Vestergaard Frandsen South Africa, are also very effective. “If we do not have access to the flexible hermetics, the rigid hermetic storage made from plastic or galvanised/stainless metals can also be used,” he said.

Both of these structures can be used as domestic, retail and commercial storage for beans and grains in general, and can protect the grains for over 12 months, as long as the air tightness is maintained.He added that even if the beans had been infested, the infested beans could be placed in air-tight containers and placed in home freezers as a cold shock treatment. This method kills all life stages of the insect within four days. Thereafter, the beans can be removed, sieved, aired and kept in air-tight containers under ambient condition as described above.

Another approach is to use a diatomaceous earth formulation otherwise called inert dust. DE branded products are safe, non-toxic products marketed in dust formulation whose effectiveness to kill insects is through its physical contact. To use, the DE dust is admixed with the beans of safe moisture content before and then bagged in a polypropylene woven bag and sealed. DEs protect grains for up to 12 months, are safe, can be eaten at any time, easy to handle and can be safely applied by all levels of stakeholders. There are commercially available DE products in the market and NSPRIDUST, developed by NSPRI, is one of them.

Inert Atmosphere System (IAS) is another approach to grains storage and in particular, beans, without the use of chemicals. The principle of this technology is to deprive the insect pest access to oxygen by replacing the air in the storage environment with nitrogen gas. Clean beans are loaded into metal silo and purged with nitrogen gas. The system is maintained with nitrogen gas to keep the environment inactive. Beans kept in this structure up to 36 months retained their food and seed qualities. Such a technology has been developed by our institute and is available at few locations in the country as Inert Atmosphere Metal Silo (IAMS).

“For industrial storage of grains and in particular beans, our institute advocate the use of Integrated Pest Management (IPM) strategies, which involve combination of several other reduced-risk control measures, including sanitation and the use of chemicals as last resort,” the NSPRI boss said.

Professor Peter added that harvested and threshed beans can be stored for short and long term periods with fumigants and chemicals using the following procedures.Beans can be stored for short term periods (not more than 3 months) by application of aluminium phosphide tablets or pellets for warehouse and conventional silo storage. This operation (although involves the use of a chemical) is very safe and is usually the first line of treatment for industrial storage of beans. But the operation must be conducted by experts under safety precautions following the manufacturers’ manual. Because fumigation leaves no chemical residues on the grains, fumigated grains can be used for immediate consumption after being aired for three days.

“For long-term storage of beans, synthetic chemicals (organophosphates, pyrethroids) can be applied as well as for empty space storage structure fumigation. The use of appropriate chemicals for grain storage is not harmful; rather it’s the improper use by untrained operators,” NSPRI said.

The situation in the country has been that these chemicals are applied indiscriminately without due regards usually by ill-informed grain merchants. The proper actions are that the procedure for use of appropriate chemicals be performed by experts under safety precautions.Beans treated directly with chemicals could be consumed after six months of storage, during which their active ingredients would have degraded.

The NSPRI boss, Professor Peter, said, “If you see that the grain is dusty and choky or has offensive odour or strange smell that is not peculiar to the grains, it may suggest that some kind of synthetic chemicals might have been used. Be careful.”Grains should be par-boiled, decanted and washed before final cooking. This will significantly reduce high levels of the chemical used to a safe limit for consumption. Grains bought for consumption should be kept at home for about two weeks before consumption. Thereafter, follow the step above for the recommended cooking procedure.”NSPRI warns that “if you are in doubt about the safety of any food, please avoid it. It is better to be hungry than to be late.”

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