Impact of pyraclostrobin on the growth of Fusarium pseudograminearum and its control efficacy against wheat crown rot in Henan Province, China

Fusarium crown rot of wheat (FCR) is mainly caused by Fusarium pseudograminearum and is a major disease in the Huang-huai wheat growing region in China, leading to a potential yield loss. In order to evaluate the effect of pyraclostrobin on the growth of F. pseudograminearum and its control efficacy, the inhibitory activity of pyraclostrobin against the growth of F. pseudograminearum was studied, and field trials of pyraclostrobin against FCR was carried out. The results showed that pyraclostrobin had strong inhibitory effect on four growth stages of F. pseudograminearum. The EC50 value of pyraclostrobin to mycelial growth was 0.1168–10.3378 μg/mL with an average of (3.5348 ± 3.0044) μg/mL, and with the shortening of branch spacing, the branching number increased as well as the bending of the hyphal apex at the edge of the mycelia. The EC50 value of pyraclostrobin on conidial germination was 0.0052–0.2498 μg/mL with an average of (0.0782 ± 0.0504) μg/mL, and there was an increased chance that conidia will germinate from intermediate cells. The EC50 value of pyraclostrobin on germ tube elongation was 0.0244–0.0605 μg/mL, which could make the middle cells of the conidia to swell and become deformed, but the teratogenic effect on the germ tube was not obvious. Pyraclostrobin can delay conidia sporulation time and make the conidia cells enlarged and deformed. The EC50 value of sporulation was 0.0170–0.0225 μg/mL. The results of field trials in Xin'an County and Yichuan County of Luoyang City showed that compared with carbendazim, pyraclostrobin had higher control effect on FCR at the jointing stage and the filling stage, with the control effect being more than 50%. It also reduced the rate of white spikes of wheat at the milky stage, but the control effect of pyraclostrobin at the filling stage decreased. At the same time, pyraclostrobin soaking increased the plant height, stem girth and 1,000 grain weight of wheat. Pyraclostrobin could be used as an alternative fungicide in the integrated management of FCR.