A zero-shot learning framework for chilli leaf disease detection, classification and severity estimation using contrastive image text representations

Agricultural productivity is severely affected by the late identification of chilli leaf diseases, which often require manual inspection and frequent model retraining. Conventional deep learning models perform well on known classes but fail to recognize unseen or emerging disease patterns. To address this limitation, we propose a Zero-Shot Dual-Encoder Framework that integrates a Vision Transformer (ViT) and RoBERTa-based semantic encoder to identify unseen disease categories and estimate their severity using lesion area ratios. The proposed model was evaluated on a curated chilli leaf dataset under various environmental conditions, achieving 98.7% accuracy, 98.0% precision, and 98.0% recall, outperforming five existing state-of-the-art approaches. Experimental findings demonstrate that the framework not only enhances recognition accuracy but also ensures scalability for real-time agricultural disease monitoring without the need for retraining.