Field evaluation of new fungicides in controlling downy mildew of broccoli - A mixed-effects model analysis

Broccoli (Brassica oleracea var. italica) is a nutritionally rich vegetable, but its production is hampered by downy mildew, caused by Hyaloperonospora parasitica. This study aimed to evaluate the efficacy of various fungicides in managing downy mildew in broccoli under field conditions during the 2021-22 and 2022-23 growing seasons. Nine treatments, including fungicidal combinations and solo products, were tested in a randomized complete block design. Disease index and yield were assessed at 15 day intervals post-application. The results showed that Fluopicolide + Fosetyl Al significantly reduced disease, with a pooled disease index (DI) of 12.77 and increased yield to 244.00 g/head, compared to untreated control with 34.43 DI and 122.00 g/head. Similarly, Famoxadone + Cymoxanil and Fenamidone + Mancozeb were highly effective, with DIs of 16.82 and 17.93 respectively, and increased yields. A regression analysis indicated a strong negative correlation between disease and yield (R² = 0.887), with each 1% increase in disease resulting in a 5.56 g/head yield reduction. The mixed-effects model analysis revealed significant treatment effects while accounting for year variability. The study concludes that integrating fungicides with different modes of action, such as Fluopicolide + Fosetyl Al, can effectively manage downy mildew while optimizing yield. This research emphasizes the need for strategic fungicide application to prevent resistance development and enhance sustainable broccoli production.