# Climatic, environmental factors and agricultural practices favoring dynamics of the spread of African cassava mosaic disease in Côte d’Ivoire

## TL;DR

The study explores how climate, farming practices, and cassava varieties influence the spread of cassava mosaic disease in Côte d’Ivoire.

## Contribution

The paper identifies key environmental and agricultural factors that strongly influence the spread of cassava mosaic disease in Côte d’Ivoire.

## Key findings

- Altitude, field density, and cropping system had the strongest influence on cassava mosaic disease spread.
- CMD incidence was higher in intercropping systems and dense fields, with whiteflies thriving in monocultures.
- Local susceptible cassava varieties are more commonly grown than resistant ones, contributing to high CMD incidence.

## Abstract

Cassava mosaic disease (CMD), caused by begomoviruses, poses a major threat to cassava leading to huge yield losses. We analyzed climatic (temperature, humidity, rainfall), non-climatic (altitude, field density, cropping system) variables and also the susceptibility of cassava varieties grown in each agroecological zone, to understand their joint influence on CMD’s spatiotemporal spread in Côte d’Ivoire. Results indicated that all factors interacted to shape CMD epidemiology, but altitude, field density and cropping system showed the strongest effects (P < 0.05). Whitefly [Bemisia tabaci] abundance declined with elevation. CMD incidence and symptom severity increased significantly with field density and were higher in intercropping systems, whereas whiteflies thrived in cassava monocultures. Of the climatic parameters analyzed, the most significant correlation was found between temperature and CMD symptom severity which were negatively linked. Humidity and rainfall exerted moderate positive effects on disease levels. The southern areas, with relatively high relative humidity and generally abundant rainfall were found to be most affected by CMD with severe symptoms. The study also showed that local susceptible cassava varieties were more frequently cultivated in the different agroecological zones studied compare to improved cassava varieties that are known more tolerant or resistant to the disease. This may explain why CMD incidence was relatively high in almost all agroecological zones. These results highlight the importance for breeding programs to integrate climatic conditions and cultural practices into targeted CMD management strategies. We encourage the implications of all stakeholders in the agriculture sector to increase their campaign disease surveillance strategies.