Detecting plant diseases is of the utmost importance as it paves the way for preventing crop diseases and maintaining the crop quality. Tomato is economically important crop, representing a fair share of dietary needs
(Sundararaman et al., 2023). It is among the most widely cultivated horticultural crops. Tomatoes are versatile and hence valuable in many food applications. Tomatoes has rich source of nutrients like vitamin C, vitamin K and antioxidants. Usually, tomatoes are grown throughout the summer season but can be grown throughout the year. However, the diversity of diseases attacking the foliar parts of this plant along with other tissues has threatened both productivity and economic viability in tomato farming
(Sundararaman et al., 2023; Attallah, 2023). Generally diseases produced from a different pathogens such as fungi, bacteria and viruses
(Kaur et al., 2023) and manifest various symptoms; hence, yield loss and economic hardship among farmers cannot be ignored
(Attallah et al., 2023; Pandiyaraju et al., 2024). This investigation considers the most prevalent tomato leaf diseases, as shown in Fig 1 a, b, c, d, e respectively. Disease identification rely heavily on expert visual inspection, which are time-consuming, often subjective and not readily scalable to large-scale agricultural operations
(Debnath et al., 2023; Chowdhury et al., 2021). Traditional method depends on the on human observers are inefficient, have poor scalability and are unreliable. To address this challenge, different image processing and computer vision techniques have been employed for the automated analysis of plant diseases
(Scharr et al., 2017; Al Farid et al., 2022). In addition, machine learning-based intelligent systems have been developed to enable automatic disease detection that provide timely intervention and improved crop management practices that contribute to enhanced agricultural productivity
(Islam et al., 2022).
Deep learning (DL) is a subfield of artificial intelligence and this has drastically transformed the character of image analysis and classification procedures (
Wagle and Harikrishnan, 2021;
Zhang et al., 2018). DL architecture, in general and the convolutional neural network (CNN) in particular, are self-learning in obtaining complex patterns and features from data in images which may lead to developing dependable and efficient strategies in the identification of diseases on the leaves of the tomato
Wagle and Harikrishnan, 2021;
Zhou et al., 2021). Many studies have proven the success of CNNs in classifying a wide range of plant diseases, including those of tomato leaves
(Attallah et al., 2023; Wagle and Harikrishnan, 2021). For leaf image classification deep learning CNN model are always better choice as compared to conventional ML algorithms as it is computationally efficient, providing highest accuracy and faster processing times. CNN are useful to automatically detect important features from the input images without manual feature extraction or human supervision. This allows them to learn hierarchical patterns and complex structures in the data, making them highly effective for leaf classification. Performance of the model can be improve by image enhancement and augmentation technique.
For the purpose of giving the accurate and efficient method in detecting and predicting the development of tomato leaf diseases. For image enhancement contrast limited adaptive histogram equalization (CLAHE) is use and augmentation technique use to expand the dataset. After that CNN architectures such as VGG16, VGG19, ResNet50 and MobileNetV2 are used for the disease classification.
Plant village dataset is use in this study for comparing different transfer learning (TL) architectures by using identical preprocessing and training conditions. Although the extensive research on tomato leaf disease classification using transfer learning, most existing studies focuses on evaluating individual CNN architectures or proposing new architectures. Limited research has been given to systematically investigating the impact of CLAHE-based image enhancement across multiple pre-trained architectures under identical experimental settings. This study addresses this gap by providing a comprehensive comparative analysis of VGG16, VGG19, ResNet50 and MobileNetV2, highlighting how contrast enhancement influences feature extraction and classification performance.
Major contributions of this work are:
1. A systematic evaluation of CLAHE-based contrast enhancement for tomato leaf disease classification using four different TL architectures.
2. An analysis of how image enhancement and augmentation affect feature learning and classification performance.
A comparative study of lightweight MobileNetV2 and deep architectures: VGG16, VGG19 and ResNet50 under identical training conditions.
3. An investigation into architecture-specific behavior for tomato disease recognition, highlighting the strengths and limitations of each model.
The organization of paper as follows:
The literature review section provides prior research in the field of identification and classification plant disease. The proposed methodology section provides the propose methodology for the classification of tomato leaf disease. The results and discussion section provides an analysis of work. Lastly, the conclusion section summarizes the study.
Literature survey
The traditional methods for detection of plant disease are mainly based on the texture, shape, color and other features of the disease spots for extraction. The technique has low identification efficiency since it relies on a vast amount of expert knowledge in agricultural diseases. Now artificial intelligence
(Rangarajan et al., 2018) has proved to be very effective in upgrading the discipline of plant science, ML and DL strategies have emerged as the two most popularly explored methodologies for the detection plant diseases. Most of the existing methods for plant disease analysis are based on disease classification (
Mane and Rangarajan, 2017;
Patil and More, 2025).
Mehta et al., (2025) presented reviews on by using DL frameworks to perform plant disease classification, thereby powering smart farming operations.
Nigam and Jain (2020) have evaluated a wide variety of deep learning algorithms for plant disease detection and identification. It was found by them that CV, ML and DL applications greatly increased classification accuracies, which led to more intelligent decision-making in agricultural applications.This section reviews recent and prominent studies focusing on automatic disease identification systems, focusing on novel, design-oriented frameworks and their applications to overcome challenges in this area of study.
Tm et al., (2018) proposed three-phase methodology, which is the collection of images of tomato leaf from plant village dataset, data pre-processing with normalization and disease classification using a modified LeNet CNN. The proposed model obtained accuracy of 94-95% that surpassed the AlexNet and GoogleNet models. ResNet (
Ahmad et al., 2020) has more layers of convolution than VGG16, which means it can better extract the details of objects. Its layer-skipping structure skips layers and overcomes the gradient vanishing problem due to deep stacking. VGG16 fails to extract detailed features for tomato leaf diseases
(Aversano et al., 2020). The deep residual network uses feed-forward neural network residual connections such that layer outputs become inputs to subsequent layers, hence improving efficiency without adding any variables or considerably increasing computation time.
Deng et al., (2021) utilized generative adversarial networks (GANs) to augment the dataset and trained different network and evaluating their performance on a test set.
Kanda et al., (2022) described the use of four diversity levels: depth size, discriminative learning rates, training-validation split ratios and batch sizes. It reached F1 score:99.5%, surpassing the performance of most existing tomato leaf disease recognition methods. Further testing is conducted on the Flavia leaf image dataset to obtain a 99.23% F1 score, signifying the reliability and efficiency of the proposed approach.
Peng et al., (2023) has described a new classification network for tomato leaf disease that combines the dense inception MobileNet-V2 with a parallel convolutional block attention module. The original images of five tomato leaf diseases were expanded to 8190 using data augmentation from 1256. An improved bilateral filtering and threshold function algorithm IBFTF was proposed to effectively filter noise out. While Dense Inception focuses on most intra-class variability but negligible inter-class differences, the PCBAM enhanced MobileNet-V2 minimizes the effects of background complexity. Empirical experiments show that the DIMPCNET achieves an accuracy of 94.44% with an F1-score of 0.9475.
Siddiky et al., (2024) applied the deep learning and image processing to enhance the detection of diseases and, therefore, food security. Five models were applied: MobileNet, ResNet50V2, Xception, InceptionV3 and VGG19. The five models were trained on 83,568 images of tomato leaves. The best validation accuracy was achieved by MobileNet at 91%, followed by the others.
Chowdhury et al., (2021) applied EfficientNet for tomato leaf disease classification in three scenarios: Two-class (healthy vs. unhealthy), six-class labels (segmented) and ten-class labels. The Adam optimizer achieved 99% accuracy for this task.
Tan et al., (2021) compared traditional machine learning techniques including KNN, SVM and RF with deep learning architectures like AlexNet, VGG16, ResNet34, EfficientNet and MobileNetV2 on the plant village dataset. Classical approach methods have achieved the accuracies between 82.10%-91.00%, whereas the deep learning model achieved the highest accuracy between 91.20% to 99.70% .
Sharma et al. (2025) proposed deep learning ensemble model based on MobileNetV2 and ResNet50 is presented for classifying the tomato leaf diseases. By training it on a Kaggle dataset consisting of 11,000 images covering 10 disease classes, the model was able to achieve state-of-the-art performance with 99.91% test accuracy. Adding layers and merging of feature maps improved the ability to extract features and reduce false classifications. This strategy enables the early detection of plant diseases, by reducing crop losses and promoting smart and sustainable agricultural practices.
Vinothini et al., (2025) developed a transfer learning-based deep learning model for the classification of tomato leaf diseases.In both the balanced setup and imbalanced setup, 4 models (AlexNet, LeNet-5, DenseNet-121 and InceptionV3) were trained using different sampling methods. The enhanced AlexNet-based model presented the best performance with accuracy, precision, recall and F1-score of 95%. This system provided a dependable means for early disease identification to help enable efficient crop management and sustainable agriculture practice.
Mezenner et al. (2025) proposed a novel fuzzy aggregation-based CNN ensemble model for tomato leaf disease classification. First, five deep learning models VGG16, ResNet152V2, MobileNetV2, InceptionV3 and DenseNet201 are pre-trained separately where different feature extractors of each model are used. These models are aggregated via a newly proposed fuzzy Max-Sum integral derived from the fuzzy convex combination operator.