The source lists chemical sprays for thrips, root grub, nematodes and leaf spot / purple blotch. Choose any product only with your local Agriculture Officer.
Follow the instructions on the product label. Consult your local Agriculture Officer before use.
Pending expert review
Source
Crop Production Guide – Horticulture Crops 2020 (Directorate of Horticulture and Plantation Crops, Tamil Nadu & Tamil Nadu Agricultural University (TNAU)), Big onion – Plant protection, pp. 151–152
