Table 2.

Research questions and their motives.

S. No.	Research Questions	Motivation
1.	RQ1: What are the main sources for collecting data about plants?	To identify different data acquisition sources that are utilized by different researchers to collect plant image data.
2.	RQ2: What different pre-processing techniques are applied?	To identify different pre-processing techniques.
3.	RQ3: What different techniques are used for data augmentation?	To identify different data augmentation techniques that are utilized for increasing the size of the dataset.
4.	RQ4: What kinds of feature extraction methods are employed?	To identify different feature extraction techniques that are utilized for extracting features.
5.	RQ5: What are the typical attributes that are used or extracted?	To identify different extracted features.
6.	RQ6: What automated systems have been implemented for identifying and categorizing plant diseases?	To identify models that are implemented for identifying and categorizing plant diseases.
7.	RQ7: What analytical techniques are employed for improving image quality?	To identify techniques utilized for improving the quality of images.
8.	RQ8: What are the techniques utilized for reducing/removing overfitting?	To identify techniques used for reducing overfitting.
9.	RQ9: What are the different plant species on which the evaluated research is based, and what classifications of diseases have been found by the evaluated studies?	To identify the species with which evaluated studies are dealing and classes of diseases identified by reviewed studies.
10.	RQ10: What is the accuracy of existing plant disease detection and classification approaches?	To identify the accuracy of existing approaches for identifying plant diseases.