Modelling the impact of multiple control strategies on the spread of phyllody disease in sesame

Abstract

Phyllody disease, caused by phytoplasma and transmitted by insect vectors such as leafhoppers, poses a serious threat to the productivity of sesame (Sesamum indicum) as it has caused substantial yield and oil‑quality losses worldwide, with documented seed‑yield reductions ranging from 38% to as high as 80% in severe outbreaks, particularly in Africa and India. Understanding phyllody dynamics is therefore critical to safeguard yields and trade. While some modeling efforts exist for sesame phyllody (for example, statistical and prediction-focused approaches), mechanistic transmission models (SEIR) assessing its full impact remain scarce. This study therefore develops and analyses impact of multiple control strategies on the control of Phyllody disease in Sesame using a deterministic compartmental mode. The model incorporates both plant and vector populations, subdivided into susceptible and infected classes, and integrates multiple control strategies; biological measures such as crop rotation and resistant seeds, chemical interventions targeting both plants and vectors, and roguing of infected plants. The effective reproduction number, , is derived using the next-generation matrix method, providing a threshold for disease spread or elimination. Moreover, the sensitivity analysis shows that the transmission rates from plants to vectors , and from vectors to plants,  are the dominant positive drivers of the effective reproduction number Re; increases in either  or  raise . In contrast, increasing the roguing rate of infected plants,  and intensifying chemical applications against leafhoppers,  substantially reduce , indicating that stronger plant removal and vector control measures are especially effective at lowering transmission Numerical simulations demonstrate that chemical control and biological interventions significantly reduce disease prevalence, particularly when combined with roguing. The findings underscore the importance of integrated management, as roguing alone is insufficient to halt disease spread. The model offers a valuable tool for guiding sustainable strategies to protect sesame crops from phyllody disease.