SPATIO-TEMPORAL DISTRIBUTION OF FUSARIUM WILT AND FLORAL VIRESCENCE, TWO MAJOR DISEASES OF COTTON IN CÔTE D’IVOIRE: AGRONOMIC IMPLICATIONS
KOUAKOUMalanno1Emailmalannokouakou@yahoo.fr
DianeGNAPI1Emailgnapidiane@gamile.com
Estelle1
KOUADIOHouphouët1,2
KOFFIKouakou1Emailkouakou10j@yahoo.fr
JeanInnocent3Emailinnocentkoffi54@gmail.com
AMANGOUANogbouFerdinand1Emailamangouaferdinand@yahoo.fr
KOUAKOUBrouJulien1Emailngoran_kouadio@yahoo.fr
KOBENANKoffiChristophe1Emailkobenankoffichristophe@yahoo.fr
KouadioN’GORAN1
Emmanuel1
KOUADIO1
AMANGOUANogbou1
Ferdinand1
BrouKOUAKOU1
Julien1
KoffiKOBENAN1
Christophe1
KouadioEmmanuel1Emailhouphouet.kouadio@gmail.com
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Entomology LaboratoryNational Center for Agronomic Research (CNRA), Cotton Research Station01 BP 633 BOUAKE 012Laboratory of Genetic Improvement and Biological ResourcesNangui Abrogoua University of Abidjan02 BP 801 Abidjan 02Côte d’Ivoire
3Department of Geography, Physical Geography LaboratoryAlassane Ouattara University of Bouaké
*KOUAKOU Malanno1, GNAPI Diane Estelle1, KOUADIO Houphouët1,2, KOFFI Kouakou Jean Innocent3, AMANGOUA Nogbou Ferdinand1, KOUAKOU Brou Julien1, KOBENAN Koffi Christophe1, N’GORAN Kouadio Emmanuel1
1National Center for Agronomic Research (CNRA), Cotton Research Station, Entomology Laboratory, 01 BP 633 BOUAKE 01
2Nangui Abrogoua University of Abidjan, Laboratory of Genetic Improvement and Biological Resources, 02 BP 801 Abidjan 02, Côte d’Ivoire
3Alassane Ouattara University of Bouaké, Department of Geography, Physical Geography Laboratory, BP 18 BOUAKE 01.
*KOUAKOU Malanno : malannokouakou@yahoo.fr
GNAPI Diane Estelle : gnapidiane@gamile.com
KOUADIO Houphouët: houphouet.kouadio@gmail.com
KOFFI Kouakou Jean Innocent: innocentkoffi54@gmail.com
AMANGOUA Nogbou Ferdinand: amangouaferdinand@yahoo.fr
KOUAKOU Brou Julien: kouakou10j@yahoo.fr
KOBENAN Koffi Christophe: kobenankoffichristophe@yahoo.fr
N’GORAN Kouadio Emmanuel: ngoran_kouadio@yahoo.fr
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Abstract
Background
Vascular fusarium wilt and floral virescence are two major cotton diseases in Côte d’Ivoire, responsible for significant yield losses. Despite their impact, current knowledge about their distribution and dynamics remains limited, as most studies date back several decades. Given this situation, it is necessary to update the data in order to better understand the evolution of diseases in the main cotton-producing areas. The objective of this study is to analyze the spatial-temporal distribution of vascular fusarium wilt and floral virescence based on monitoring carried out on 600 smallholder plots between 2022 and 2024.
Results
The results of the seasonal variation show that the incidence of fusarium wilt varies from one crop year to another, with no statistically significant difference between the three seasons (p = 0.351). Spatially, the disease is mainly localized in the southern part of the cotton basin (below the 9th parallel), with three foci identified in the northern part. With regard to floral virescence, the seasonal dynamics exhibit a nearly similar pattern across the three cropping seasons, with varying levels of incidence. The 2022 cropping season exhibited the highest incidence rates. Unlike fusarium wilt, inter-season variations in floral virescence are statistically significant. The most affected areas are mainly located in the North of the cotton basin (above the 8th parallel).
Conclusion
These results highlight the need to implement targeted phytosanitary strategies, including vector control and the introduction of resistant cotton varieties. They may also guide the choice of plots for seed production.
Keywords:
Vascular fusarium wilt
floral virescence
Cotton
Côte d’Ivoire
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Introduction
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Cotton (Gossypium spp.) is a key pillar of socio-economic development in Côte d'Ivoire, particularly in the central and northern regions. Ranked as the fourth most important agricultural exports after cocoa, rubber, and cashews nuts, cotton contributes approximately 1.7% of Côte d'Ivoire's gross domestic product (GDP) and accounts for 7% of its exports (Markus and Francis, 2010). Cotton cultivation directly and indirectly sustains approximately 3 million individuals, accounting for nearly 10% of the national population (Koffi, 2013). Income from cotton enables rural households to invest in education, health, and other economic activities (Rathore et al., 2015). In 2024/2025, production was estimated at 351,764 tonnes, with growth targets for subsequent seasons (PR-PICA, 2025). However, its sustainability is threatened by biotic constraints.Among these challenges, vascular fusarium wilt and floral virescence stand out for their growing economic impact. Fusarium wilt, caused by the soil-borne fungus Fusarium oxysporum f. sp. vasinfectum, affects the vascular tissues of cotton plants, leading to progressive wilting, browning of the vessels, premature leaf drop, and, in severe cases, plant death (Man et al., 2022). Since 2022, the incidence of vascular fusarium wilt has increased in the Ivorian cotton basin (Kouamé et al., 2024). Floral virescence, on the other hand, is caused by a phytoplasma, whose vector is the leafhopper Orosius cellulosus. It manifests itself through morphological abnormalities: transformation of flowers into leaf-like structures, proliferation of axillary buds, and floral sterility, drastically reducing yield (Laboucheix, 1986). Floral virescence was present in northwestern Côte d'Ivoire along the Séguéla-Odienné axis. The agricultural losses caused by these diseases are in the order of 15 to 25% of production for fusarium wilt (Sayegh, 2009) and 100 kg/ha and 184 kg/ha from one area to another for floral virescence (Soro, 2020).
The work of Koné et al. (2017) highlighted spatial and temporal variability in rainfall and temperature in the Ivorian cotton basin. These climatic parameters play a crucial role in exacerbating floral virescence and vascular fusarium wilt. In addition to these biotic factors, farmers' cultivation practices significantly influence the management of these diseases. Climatic heterogeneity and variable agricultural practices complicate the health management of these diseases. Although these diseases pose a threat to cotton production, public scientific knowledge about them dates back several decades. However, updating knowledge about these diseases is necessary to adapt the health management of cotton cultivation. In light of these challenges, the spatio-temporal mapping of these two diseases together becomes essential to guide integrated management programs, taking into account the selection of resistant varieties and technical support for producers. With this in mind, this study analyzes the spatial and temporal distribution of fusarium wilt and floral virescence in the cotton basin of Côte d'Ivoire in order to better understand their dynamics and propose sustainable solutions.
Materials and methods
Materials
The materials consist of cotton varieties of the species Gossypium hirsutum, developed by the National Agricultural Research Center (CNRA) of Côte d'Ivoire and grown by producers.
Methods
The health monitoring system comprised a total of 600 plots in rural areas spread across 60 cotton administrative zones. The plots were distributed across the different sowing decade (Table 1). Ten plots were selected per administrative zone. The plots were subjected to the window program consisting of six insecticide treatments currently implemented for the phytosanitary protection of cotton crops.
Abréviation | North | South |
|---|---|---|
D1 (May 20–31) | 1 | |
D2 (June 01–10) | 2 | 1 |
D3 (June 11–20) | 3 | 3 |
D4 (June 21–30) | 2 | 3 |
D5 (July 01–10) | 1 | 2 |
D6 (July 11–20) | 1 | 1 |
Total by locality | 10 | 10 |
Field Plot observation
Sanitary data were collected by technicians from cotton structures in the Ivorian cotton basin, who were trained to carry out this activity. Disease monitoring (Fusarium wilt and floral virescence) was carried out weekly. The observation area was of 10 rows x 20 meters. Plants showing symptoms of Fusarium wilt and floral virescence were identified and marked with a string. Affected plants were then counted, with the string left in place to prevent recounting the following week. Data were collected during the 2022, 2023, and 2024 cropping seasons.
Data analysis
Data analysis began with verification of validity conditions (normal distribution and homogeneity of variances) prior to performing one-way analysis of variance (ANOVA I). The qqplot graphical representation and Levene's test (at a 5% threshold) showed that the data met the conditions for performing the ANOVA I test.
The ANOVA I test was performed to determine the effect of geographical area and agricultural season on fusarium wilt and floral virescence. When a significant difference was observed at the 5% threshold, Tukey's HSD post hoc test was performed to determine homogeneous groups using Mendiburu's agricolae package (2021). A spatial distribution was carried out to assess the geographical distribution of these two diseases. The levels of evolution of the two diseases over time were determined using the ggplot2 package (Wickham, 2016).
The analyses were performed using R software 4.1.2 (R Core Team, 2021). Data spatialization using ArcGIS 10.2.2 software (Esri, 2014).
Results
Seasonal variation in fusarium wilt and floral virescence
Figure 1 and 2 show the seasonal evolution of fusarium wilt and floral virescence, respectively, during the 2022 to 2024 agricultural seasons, over the period from July to November.
The spreading of fusarium wilt was relatively low during the 2023 and 2024 growing seasons, with infestation levels ranging from 0–1%. In contrast, the 2022 crop year recorded the highest levels. Peaks were observed during the weeks of July 29 (2.3%), August 12 (2%), and September 16 (6.6%). After the latter date, a sharp decline in infestation levels (0%) was noted, which persisted until the end of the cotton growing cycle.
With regard to floral virescence, the pattern of curves were broadly similar across the three crop years. The disease effectively appeared starting from the week of July 29 each year. The 2022 season recorded higher prevalence levels than the other two seasons, with a notable peak during the week of September 2 (25%). From that date onwards, a gradual decline was observed in all three seasons.
Fig. 1
Seasonal evolution of the percentage of cotton plants affected by fusarium wilt during the 2022 to 2024 crops year.
Fig. 2
Seasonal evolution of the percentage of cotton plants affected by floral virescence during the 2022 to 2024 crop year.
Crop year effect of fusarium wilt and floral virescence
The results of the analysis of variance presented in Table 2 made it possible to evaluate the effect of the crop year on fusarium wilt and floral virescence. No significant effect of the crop year was observed on fusarium wilt (p = 0.351). However, a very significant effect of the growing season was observed on floral virescence (p = 0.007).
Parameter | Df | Sum Sq | Mean Sq | F value | Pr(> F) |
|---|---|---|---|---|---|
Fusarium wilt | 2 | 0.0118 | 0.0059 | 1.053 | 0.351 |
Floral virescence | 2 | 0.405 | 0.20243 | 5.038 | 0.007 |
Effect of geographical areas on fusarium wilt and floral virescence
Analysis of variance revealed a highly significant effect of geographical zones on floral virescence (p < 0.001). However, no significant effect was observed on fusarium wilt (p = 0.0539) (Table 3).
Parameters | Df | Sum Sq | Mean Sq | F value | Pr (> F) |
|---|---|---|---|---|---|
Fusarium | 58 | 0.4062 | 0.007004 | 1.424 | 0.0539 |
Floral virescence | 58 | 4.499 | 0.07757 | 3.159 | < 0.001 |
Spatial distribution of fusarium wilt and floral virescence
The spatial distributions of fusarium wilt and floral virescence are illustrated in Figs. 3 and 4, respectively. Fusarium wilt is mainly found in the southern part of the cotton basin. The rate of affected plants varied from 0 to 0.3% per plot, with outbreaks observed in Komboro, Madinani, and Morondo. As regards Floral virescence is mainly found in the northern part of the cotton basin, with a few outbreaks in the south. It was most prevalent in Mankono, Morondo, Kani, Komboro, Sordi, Tehini, and Diawala, with proportions ranging from 0.3 to 0.7 plants 
affected.
Fig. 3
Spatial distribution of fusarium wilt incidence in the Ivorian cotton basin during the period 2022–2024
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Figure 4. Spatial distribution of the incidence of floral virescence in the cotton basin during the period 2022–2024Discussion
The results obtained in this study shed light on the spatio-temporal dynamics of vascular fusarium wilt and floral virescence in the cotton basin of Côte d'Ivoire. The joint analysis of epidemiological data and statistical and cartographic results revealed significant trends, both seasonally and across the different agroecological area studied. These results also reveal the existence of differented epidemiological dynamics between these two pathologies, suggesting distinct mechanisms of evolution and propagation depending on environmental factors and agronomic practices specific to each area.
The marked seasonal evolution of fusarium wilt observed during the 2022 crop year, compared to the other two seasons, suggests the influence of climatic conditions particularly favorable to the expression of this disease. Indeed, this season was characterized by high relative humidity accompanied by a decrease in rainfall (Kouadio et al., 2024), conditions known to favor the development of fusarium wilt (Manstretta & Rossi, 2015 ; Cruz et al., 2019).
Furthermore, spatial distribution shows that fusarium wilt is mainly localized in the southern part of the cotton basin, below the 9th parallel, with notable outbreaks identified in Vavoua, Mankono, Tieningboue, Bouandougou, Marandala, and Komboro. Thus, the selection of plots for cotton seed production in these areas must be carried out with great care in order to limit the risk of spreading this disease to other production areas.
With regard to floral virescence, a comparable seasonal trend was observed over the three crop years, although the most significant damage was observed during the 2022 crop year. The high interannual variability observed suggests that factors intrinsic to each crop year, particularly climatic conditions and producers' sanitary practices, strongly influence the intensification of the disease.
This disease is transmitted by an insect vector belonging to the Cicadellidae family, Orosius cellulosus (Laboucheix et al., 1972 ; Follin, 1982). However, climatic parameters such as temperature and rainfall directly influence the dynamics of leafhopper populations and, consequently, the extent of the damage. According to Koné et al. (2017) and Kouadio et al. (2024), the decrease in rainfall combined with the rise in temperatures contribute to accentuating the damage and worsening the symptoms caused by leafhoppers. This phenomenon was observed during the leafhopper crisis in the 2022 agricultural season (Kouadio et al., 2024), which could explain the particularly high level of damage recorded in this crop year compared to the 2023 and 2024 crop years.
In addition to climatic factors, farming practices also play a role in the spread of virescence. In addition to transmission by Orosius cellulosus, the mycoplasma can spread through contact between a healthy cotton plant and a contaminated plant, whether it is another cotton plant or host plant species such as Sida cordifolia L., S. rhombifolia L., Sesamum indicum L. (Pedaliaceae), Sida sp. and Sida spp. (Laboucheix et al., 1973). These plants, considered weeds, are tolerated by some farmers in cotton fields, even though they are important reservoirs of the disease.
Floral virescence and vascular fusarium wilt of cotton in Côte d'Ivoire, initially localized respectively in the northwest (Séguéla-Odienné axis) and the central and southern areas of the cotton basin, undergone both geographic expansion and increased in incidence over the past 35 years. This dynamic is mainly attributable to the use of susceptible varieties, climate change altering environmental conditions favorable to pathogens, inadequate cultural practices such as negligent in seed treatment and distribution of contaminated seeds, as well as the erosion of natural enemies of vectors and the involvement of nematodes as aggravating factors. These diseases, notably caused by Fusarium oxysporum f. sp. vasinfectum in the case of fusarium wilt, result in yield losses exceeding 15%, thereby compromising seed production and causing significant economic and social impacts. Integrated management, combining the use of resistant varieties (such as the Gouassou Fus1 cultivar), the adoption of good agricultural practices, and adaptation to climatic constraints, is essential to limit the spread of these diseases and to ensure the sustainability of the Ivorian cotton sector
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The identification of high-incidence areas is essential for implementing targeted interventions, such as developing specific phytosanitary programs to combat vectors, introducing resistant cotton varieties, or installing physical barriers. A drainage system must also be put in place to prevent overly wet soil, which would contribute to the persistence of fusarium wilt. These measures will limit the spread of floral virescence and fusarium wilt.Conclusion
This study highlighted the spatial-temporal dynamics of vascular fusarium wilt and floral virescence in the Ivorian cotton basin. It laid the foundations for understanding the evolution of these two diseases in the Ivorian cotton basin. Historically confined to the south of the basin, below the 9th parallel, fusarium wilt is now showing a tendency to spread northward, thus expanding its infestation area beyond its traditional limits. As for floral virescence, it mainly affects the northern part, above the 8th parallel, with a gradual spread toward the center and south of the cotton basin. These results suggest differentiated epidemiological dynamics and distinct mechanisms of evolution and spread depending on the area and crop year.
From an agronomic standpoint, this study allows the following recommendations to be made :
- Avoid producing cotton seeds in areas where fusarium wilt is present;
- use the tolerant varieties proposed by research;
- ensure proper seed treatment before sowing.
An in-depth study of the pathogens of these two diseases, their mechanisms of spread, and the resistance mechanisms of cotton plants is necessary to develop a control strategy that will manage them effectively.
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DeclarationsEthics approval and consent to participate
Note applicable
Consent for publication
Note applicable
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Availability of data and materials
The results presented in this study are based on data collected directly by the research team in the cotton fields.
Competing interests
The authors declare that they have no competing interest concerning this article.
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Funding
Note applicable.
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Authors' contributions
GNAPI Diane Estelle commented on, interpreted, and drafted the manuscript. KOUADIO Houphouët contributed to the statistical data analysis and writing and reviewed and revised the manuscript. KOUAKOU Jean Innocent contributed to the development of the maps showing the geographical distribution of disease incidence. KOUAKOU Malanno, the initiator of the research activity, developed the methodology implemented, provided the data, guided the research, and reviewed and revised the manuscript.
Acknowledgements
The authors are grateful to the interprofessional cotton organization (INTERCOTON), the Interprofessional Fund for Agricultural Research and Advice (FIRCA), and all the cotton companies that contributed to the collection of field data.
Authors' information
KOUAKOU Malanno : https://orcid.org/0000-0001-7583-8025
GNAPI Diane Estelle : https://orcid.org/0009-0000-5087-2198
KOUADIO Houphouët: https://orcid.org/0000-0002-8238-1091
KOFFI Kouakou Jean Innocent: https://orcid.org/0009-0005-5139-6927
AMANGOUA Nogbou Ferdinand: https://orcid.org/0009-0002-0191-4464
KOUAKOU Brou Julien: https://orcid.org/0009-0000-1634-0227
KOBENAN Koffi Christophe: https://orcid.org/0000-0002-2019-3394
N’GORAN Emmanuel: https://orcid.org/0009-0006-1916-7398
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