Abstract:

Zizania latifolia is an important aquatic vegetable in China. However, there are few registered pesticides for it, leading to a common issue of off-label pesticide use. The inappropriate use of fungicides can easily result in reduced pregnancy rates and other phytotoxicities in Z. latifolia. This study selected nine commonly used fungicides for field and laboratory experiments to evaluate their impact on Z. latifolia pregnancy. The field experiment results showed that Z. latifolia pregnancy stage is not suitable for the use of azoxystrobin, triadimefon, flutriafol, and tebuconazole. After three consecutive applications, the pregnancy rates were only 39.44%, 27.76%, 21.64%, and 10.37%, respectively. It is also not advisable to use tebuconazole and azoxystrobin 30 days before the pregnancy stage of Z. latifolia, as the pregnancy rates were only 30.77% and 11.70%, respectively after a single application. The laboratory experiment results indicated that the EC₅₀ values of the nine fungicides for inhibiting the growth of the Ustilago esculenta haploid strain MT3 ranged from 0.017 5 mg·L^-1 to 8.470 6 mg·L^-1, with tebuconazole having the lowest EC₅₀ value. However, the EC₅₀ value ranking of the nine fungicides did not align with their field performance, suggesting that the impact of fungicides on Z. latifolia pregnancy in the field is a comprehensive result of the actual dosage acting on the U. esculenta and possible metabolic products.

Key words: fungicides, Zizania latifolia, Ustilago esculenta, pregnancy