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Detection and spatial distribution of pesticides in cocoa farming in Ivory Coast

This study quantifies the widespread contamination of water, soil, and cocoa beans by 22 approved pesticides across ten sites in Ivory Coast, revealing that fungicides like pyraclostrobin dominate due to the high prevalence of pod rot and that southern wetter areas exhibit higher concentrations, thereby highlighting the urgent need for monitoring and understanding pesticide transfer to ensure sustainable production and protect human and environmental health.

Original authors: Adama Soro, Maurice Millet, Sylvia Georg, Catherine Galindo, Gaetana Quaranta

Published 2026-07-15

📖 5 min read🧠 Deep dive

CC BY 4.0

Original authors: Adama Soro, Maurice Millet, Sylvia Georg, Catherine Galindo, Gaetana Quaranta

Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). ✨ This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer

Imagine the Ivory Coast as the world's chocolate factory, churning out more than 40% of the cocoa beans you see on supermarket shelves. But behind the scenes, the cocoa trees are fighting a constant, invisible war. They are besieged by a "horde of villains": fungi that rot the pods, bugs that eat the leaves, and viruses that make the branches swell up like balloons. To win this war, farmers have been handed a massive arsenal of chemical weapons: pesticides.

This study is like a detective story where researchers went on a three-year scavenger hunt across 10 different cocoa plantations. They didn't just look at the trees; they checked the soil, the running rivers, the water in underground wells, and the cocoa beans themselves to see where these chemical weapons ended up.

The Big Reveal: The Fungus Fighters Win (and Overstay)
The main finding is a bit like finding that the security guards (fungicides) are the only ones who never leave the party. Out of 22 different chemicals the team was tracking, fungicides were the most frequent guests found in every single place they looked.

Why? Because the trees are terrified of "pod rot," a fungal disease that can wipe out 30% to 40% of the harvest. It's the number one health scare for the farmers. So, they spray heavily. The star player of this group is a chemical called pyraclostrobin. It was found everywhere, acting like a ghost that haunts the soil, the water, and the beans.

The Great Migration: Where the Chemicals Go
The researchers mapped out how these chemicals travel, and the journey depends on the chemical's personality:

The Runners (Groundwater): Some chemicals are like sprinters who love to dive deep. Cyproconazole and pyraclostrobin are highly soluble and persistent. They don't just sit on the surface; they get washed by the heavy tropical rains straight down into the groundwater. In fact, in the underground wells, cyproconazole was found 100% of the time, and pyraclostrobin 88% of the time.
The Runaways (Surface Water): Other chemicals prefer to slide off the top. Metamitron, a weed killer, is like a slippery fish that washes right off the soil into the rivers and streams. It was found in 100% of the surface water samples.
The Stayers (Soil): Some chemicals are like Velcro. They stick tightly to the dirt. Imidacloprid and pyraclostrobin were found in 90% of the soil samples, clinging to the ground.

The "Forbidden Fruit" Problem
Here is where the plot gets twisty. The study found some chemicals in the water and soil that are actually banned in the European Union (the main buyer of Ivory Coast cocoa).

Bifenthrin (an insecticide) and Alachlor (a herbicide) were detected.
The paper suggests a likely explanation for this: farmers might be using old stocks of these banned chemicals because they are still on the official "approved" list for cocoa in Ivory Coast, even though the EU says "no way."
The authors point out a "boomerang effect": chemicals banned in Europe are being exported to Africa, used there, and then the residues end up returning to Europe on the cocoa beans.

The Chocolate Check: Are the Beans Safe?
When the team tasted the test results (metaphorically speaking, by analyzing the beans), they found that fungicides were the main contaminants in the cocoa beans too.

Pyraclostrobin was the big offender. In two specific plantations (Alépé and Soubré), the levels of this chemical in the beans were 0.18 mg/kg and 0.16 mg/kg respectively.
The paper compares this to the legal limit set by the International Cocoa Organization and the EU, which is 0.1 mg/kg.
The Verdict: The paper states clearly that these levels exceed the maximum allowed limit. It does not say the beans are "safe" or "unsafe" in a medical sense, but it confirms they break the legal rules for export.

What the Paper Clarifies
The study explicitly clarifies the role of different factors without dismissing them entirely:

It clarifies that while herbicides are used, they are the least quantified and least found chemicals in the water and soil compared to fungicides. They are not the primary contaminant, but their use is noted as increasing, particularly for fighting swollen shoot disease.
It clarifies that the GUS index (a simple math formula used to predict if chemicals will leak into groundwater) is a useful, easy-to-calculate tool, but it is not perfect. The paper notes that even chemicals the formula predicts "won't move" (like pyraclostrobin) are still showing up in groundwater. The authors suggest the formula is too static and needs to be supplemented with empirical data because it doesn't fully account for heavy tropical rains, specific soil types, or agricultural practices.

The Bottom Line
The study concludes that the current strategy of heavy chemical use is working to fight the pests, but it's creating a "chemical soup" in the environment. The chemicals are moving from the soil to the water and into the beans. The authors suggest that while the "2QC" program (a national plan to boost cocoa production) helped farmers get these chemicals, the next step needs to be a serious look at how to reduce the use of these tools and monitor them better.

The paper doesn't claim to have "solved" the problem or found a magic cure. Instead, it provides a clear, measured map of where the chemicals are, proving that the fight against cocoa pests has a heavy environmental cost that needs to be managed.

Technical Summary: Detection and Spatial Distribution of Pesticides in Cocoa Farming in Ivory Coast

Problem Statement
Ivory Coast, producing over 40% of the world's cocoa, faces significant agricultural challenges due to its sub-equatorial and humid tropical environment, which fosters a diverse array of bio-aggressors including fungal diseases (e.g., Phytophthora megakarya causing pod rot), viral diseases (Cocoa Swollen Shoot Disease), and insect pests. The primary national response, the "2QC" program (2014–2023), has relied heavily on chemical protection, specifically the distribution of free pesticides to farmers. While this strategy aims to secure production, the intensive use of pesticides raises concerns regarding environmental contamination and public health. There is a critical lack of data regarding the fate of these pesticides in tropical contexts, specifically their transfer between soil, water, and cocoa beans, and their spatial distribution across the production basin.

Methodology
The study conducted a comprehensive analysis across ten randomly selected cocoa plantations spanning the entire Ivorian production basin (from the "new cocoa belt" in the southwest to the east). Sampling occurred over three years during the dry season.

Matrices Analyzed: Surface water, groundwater (wells and boreholes), soil, and cocoa beans.
Target Analytes: 22 pesticide molecules from the official list approved for cocoa cultivation in Ivory Coast, categorized as insecticides (11), fungicides (7), and herbicides (4).
Sampling and Extraction:
- Soils: Collected per Codex Alimentarius/FAO standards, dried, and extracted via Pressurized Liquid Extraction (PLE) using acetonitrile.
- Water: Surface and groundwater samples were filtered and extracted using Celite (diatomite) cartridges.
- Cocoa Beans: Fresh beans were fermented, dried, and crushed. Extraction followed the QuEChERS method.
Quantification:
- GC-MS: Used for non-polar and semi-polar compounds (e.g., pyrethroids, organochlorines).
- LC-MS/MS: Used for polar compounds (e.g., neonicotinoids, certain fungicides).
Analytical Framework: Detection frequencies (FD) were correlated with physicochemical properties, specifically the organic carbon-water partition coefficient ( $K_{oc}$ ), half-life ( $DT_{50}$ ), and the Groundwater Ubiquity Score (GUS) to model leaching potential.

Key Results

Universal Contamination: All ten sites and all four matrices (soil, surface water, groundwater, cocoa beans) showed contamination.
Dominance of Fungicides: Fungicides were the most frequently detected class across all matrices. Pyraclostrobin was the primary contaminant, followed by Cyproconazole. This prevalence is attributed to the high economic losses (30–40%) caused by pod rot, making fungicides the primary health concern for farmers.
Spatial Distribution:
- Southern/Wet Regions: Sites below 5.5°N (e.g., Aboisso, Alépé, Divo) showed the highest concentrations and frequencies of fungicides, correlating with dense humid evergreen forests and high disease pressure.
- Northern/Drier Regions: Sites in the north (e.g., Daloa, Biankouma) showed higher proportions of herbicides, linked to the need for chemical weeding due to labor shortages and specific disease management (CSSD control).
- Insecticides: Detected across the basin but were generally less dominant than fungicides, except in specific contexts like the San Pedro region.
Transfer Mechanisms (Soil to Water):
- Groundwater: Cyproconazole (100% FD) and Pyraclostrobin (88% FD) were dominant in groundwater. Their high solubility and persistence facilitated leaching.
- Surface Water: Metamitron (herbicide) showed 100% FD, likely due to runoff given its low $K_{oc}$ . However, fungicides still contributed 52% of total contamination in surface water.
- GUS Index Limitations: While the GUS index predicted high leaching for Cyproconazole, Imidacloprid, and Thiamethoxam, Imidacloprid and Thiamethoxam were found frequently in soil but less so in groundwater, suggesting that factors beyond static indices (e.g., rainfall intensity, soil texture, biological degradation) influence transfer in tropical environments.
Regulatory Compliance:
- Water: Most residues were below regulatory thresholds (0.1 µg/L per molecule). However, Pyraclostrobin exceeded the 0.1 µg/L limit in groundwater at Divo (0.21 µg/L) and Soubré (0.12 µg/L).
- Cocoa Beans: Systematic exceedances of the default Maximum Residue Limit (MRL) of 0.01 mg/kg were observed for Pyraclostrobin. Specific exceedances were recorded at Alépé (0.18 mg/kg) and Soubré (0.16 mg/kg) against a specific MRL of 0.1 mg/kg.
- Banned Substances: Bifenthrin, prohibited in the EU but approved in Ivory Coast, was detected in surface water and groundwater, highlighting a regulatory disconnect between producing and importing markets.

Significance and Claims
The paper claims to provide the first concomitant analysis of pesticide residues across water, soil, and cocoa beans in diverse zones of Ivory Coast's cocoa basin. The study highlights that while fungicides are necessary to combat devastating crop diseases, their omnipresence poses significant environmental risks, particularly regarding groundwater contamination and residue accumulation in the final product.

The authors assert that the current reliance on chemical control, driven by the "2QC" program, has consequences for the "One Health" concept, affecting both the environment and human health. They emphasize that the transfer of pesticides is complex in tropical settings, influenced by high rainfall and specific soil characteristics, which may not be fully captured by standard leaching indices like GUS.

Conclusion
The study concludes that pesticide monitoring is essential to reduce environmental impacts and ensure sustainable production. It calls for a re-evaluation of pesticide use strategies by Ivorian authorities and the Coffee and Cocoa Council (CCC) post-2QC program, advocating for reduced chemical dependency, the promotion of alternatives, and the establishment of regular monitoring mechanisms to protect both local ecosystems and international export markets.

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