Maize is one of the main cereal crops in the world. Its global annual production is estimated at 2.5 billion tons, making it a pillar of food security [1]. The size of the African maize market is estimated at USD 41.40 billion in 2024 and is expected to reach USD 57.26 billion by 2029 [2]. In Burkina Faso, maize ranks second in cultivated area and first in production [3]. It is an important crop for the country’s food security and socio-economic development, which underscores its significance in the presidential initiative and the agropastoral offensive [4].

Despite this importance, its production faces biotic constraints, including viral diseases. The maize streak virus (MSV) is one of the main diseases affecting maize. In the field, yield losses of up to 100% can be recorded, depending on the variety and stage of infection of the crop [5]. The virus is transmitted by at least 6 species of leafhoppers from the genus Cicadulina (Homopteracicadulidae) in a persistent manner [6]. MSV is capable of infecting over 80 other species in the Poaceae family [7], including wheat, sorghum, millet, and sugarcane [8]. In general, the proposed control strategies against the disease include the removal of infected plants and chemical control of the vector and have not effectively managed the emergence of the disease. The work conducted by Asare-Bediaket al., Alegbejo et al., and Mbong et al. has shown that several factors are involved in the transmission mechanism of this virus and in the epidemiology of the disease [9]-[11]. In this same vein, several authors have demonstrated the influence of agro-ecological factors on the emergence of MSV affecting maize, particularly in Nigeria [12] and in Cameroon [11].

In Burkina Faso, significant information has been generated regarding, on one hand, the biological and serological variability of the virus [13][14] and, on the other hand, the transmission mechanisms [15]. However, knowledge about the epidemiology of this viral disease remains fragmentary and outdated. Indeed, there is insufficient recent data available on the incidence and distribution of MSV in Burkina Faso. Furthermore, the existing knowledge regarding the main transmission pathways of MSV is not enough to fully understand the epidemiology of this viral disease. In this context, the current study was initiated to contribute to providing information on the epidemiology of MSV in Burkina Faso. The objective of this study was to assess the incidence and distribution of MSV in the Sudanian and Sudan-Sahelian zones of Burkina Faso.

The temporal development of vector-transmitted viral diseases constitutes a multifaceted and dynamic process. It is marked by a multitude of actions, reactions, and interactions among the pathogen, vector populations, host plants, and the abiotic elements of the environment. In the specific case of maize streak virus (MSV), the subject of our study, the results demonstrate that the disease exhibits an uneven distribution across the Burkinabe territory due to distinctive variations among the country’s three agro-climatic zones.

The Sudanian zone exhibits a significantly higher incidence and severity of streak than the Sudano-Sahelian zone. These findings are consistent with those reported by Konaté and Traoré [13], who observed a gradual decrease in the incidence and severity of MSV when transitioning from the Sudanian zone to the Sudano-Sahelian and Sahelian zones. Quantitative variations in vegetation cover across different agro-climatic zones could provide explanations for the observed spatial distribution of MSV. Indeed, the Sudanian zone is characterized by a more abundant grass flora compared to the Sudano-Sahelian zone. It is the most wooded and harbors the highest number of reservoir hosts compared to the Sudano-Sahelian zone, which is more sparsely populated with trees and shrubs (savannah). The incidence and severity of streak evolve depending on the development of the vector insect (cicadulina), which in turn relies on the abundance of reservoirs and host grasses. These statements are partly in line with those of Alegbejo et al. and Magenya et al., who state that the population size of leafhoppers is mainly determined by the abundance of host grasses [12][18]. Additionally, Seydou et al. counted approximately 3 infected plants per square meter (m²) in the Guinean northern zone, around 1 plant per m² in the Sudanian savannah zone, and less than 1 plant per m² in the Sahelian zone [15].

High levels of humidity appear to contribute to the development of leafhoppers. In all 100 inspected fields, the incidence and severity observed under the trees are higher than those recorded in the clearings. Since humidity is generally higher in shady areas than in open areas, the higher incidence of MSV in the shade is likely linked to these high humidity levels. These results are consistent with those of Dabrowski [19], who concluded that humidity can be a limiting factor for the complete development of the insect. Similarly, Bosque-Pérezet al., Alegbejo et al., and Magenya et al. [12][18][20] argue that the experimental breeding conditions for the vector used by several authors involve high levels of relative humidity.

Trees serve as ecological niches, providing shelter and protection for leafhoppers against inclement weather, especially heavy rains and strong winds. It was revealed that fields with a high density of trees have higher incidences. Trees clearly play an attractive role for leafhoppers. These findings align with those of Asanzi etal. [21], who confirm that biotic factors (host plants) and abiotic factors (humidity, temperature) have been reported to influence the movement and feeding behavior of leafhoppers.

Localities located in the southern part of the country (Sudanian zone) show higher incidences compared to localities in the Sudano-Sahelian zone. These disparities in streak incidence are linked to the agro-climatic characteristics of each locality. In Burkina Faso, the rainfall pattern is unimodal, with the first rains typically arriving in April-May in the South and gradually spreading to the northern part of the country. During these initial weeks of rainfall, wild herbaceous flora gradually establishes, thereby attracting leafhoppers sheltered in the reservoir host plant. This first generation of leafhoppers develops rapidly and then migrates to infest nearby maize fields. Additionally, in localities located in the South, the rainy season is longer (six months) and gradually decreases as one moves towards the North of the country. This situation influences the rapid regeneration of host grasses, which in turn favors the development of leafhoppers and the spread of the disease. These statements align with those of Asanzi [22], who states that the size of the vector population is mainly determined by the amount of host grasses available for egg-laying and nymph development, and the growth of host grasses depends on rainfall. During a study on the epidemiology of MSV, Konaté and Traoré [13] reported that at the end of the rainy season, humidity gradually decreases to values below 30%. Only a small proportion of insects survive, and the size of this residual population influences the availability of the vector at the beginning and throughout the new rainy season. This phenomenon ultimately impacts the incidence of the disease.

In the experimental plots, all 12 varieties of maize exposed to natural MSV infection developed streak symptoms with a very low incidence ranging from 0.47% to 1.41% across all study sites. These preliminary results could be attributed to the low pressure of the MSV vector insect in these experimental plots, which are located in fully open areas. Such an assessment did not confidently lead to the selection of resistant or tolerant varieties to MSV. Under these circumstances, evaluating the material in a semi-controlled environment becomes necessary.

This study demonstrates that the incidence and severity of maize streak virus disease vary depending on the localities and agro-ecological zones of Burkina Faso. The results revealed a very high incidence in the Sudanian zone and a moderate incidence in the Sudano-Sahelian zone. The disease incidence is higher in fields with significant shading compared to fields with fewer trees. The 10 inspected regions were classified into 4 groups based on the level of incidence. The regions of Bankui, Kuilsé, and Nakambé have a low incidence, Kadiogo, Oubri, and Nando have a moderate level, Nazinon and Djôrô have a high incidence, and Tannounyan and Guiriko show a very high incidence. This variation in infection rates is linked to the climatic characteristics of each locality and zone, which significantly influence the diverse development of MSV host plants. This, combined with the abundant presence of vectors, the cultivation of MSV-sensitive cultivars, and favorable environmental conditions (early and irregular rains, suitable humidity and temperature), is the root cause of MSV epidemics. A study on the molecular characterization of the virus would be necessary and could contribute to the development of control strategies.

The authors wish to thank INERA (Institute of Environment and Agricultural Research) and University of Joseph Ki-Zerbo for collaboration on this work. Gratitude goes especially to the farmers in all the AEZ for accepting working on their farms and for the important information provided for this work.