The correct identification is (D) Alternaria blight.
Analysis of each option follows:
(A) White rust: A fungal pathogen, specifically Albugo candida, causes this disease, impacting rapeseed-mustard crops. While a disease and not a pest, it is a prevalent issue for these crops.
(B) Stalk borer: This is a pest that targets the stems of rapeseed and mustard plants, with its larvae consuming stem tissue and causing substantial damage.
(C) Aphids: These are pests that extract sap from plants, thereby weakening them and increasing their vulnerability to diseases. Aphids are frequently encountered pests on rapeseed and mustard crops.
(D) Alternaria blight: Caused by the Alternaria fungus, this is a fungal disease affecting rapeseed-mustard crops. It is categorized as a disease, not a pest, and manifests on the plant’s leaves, stems, and pods.
Consequently, Alternaria blight (option D), being a disease and not a pest, is the correct answer.
| List-I (Name of crop) | List-II (Disease of crop) |
| (A) Paddy | (I) Red rot |
| (B) Cotton | (II) Loose smut |
| (C) Groundnut | (III) Tikka (Leaf spot) |
| (D) Gram | (IV) Rust |