Performance of chlorothalonil levels and spraying intervals on Asian rust control and soybean grain yield

ABSTRACT In an experiment conducted in the field, during the 2017/18 growing season, with the soybean cultivar Syn 1561 IPRO, the interaction of chlorothalonil levels with application intervals was evaluated for the control of Asian soybean rust, caused by Phakopsora pachyrhizi. The first fungicide application was performed in V8 stage, 44 days after emergence, with 1.85% rust leaflet incidence. The experiment consisted of a factorial arrangement with five fungicide levels (1.0, 1.5, 2.0, 2.5 and 3.0 L/ha) applied at 8, 12 and 16-day intervals, using randomized block treatments and four replicates. A self-propelled sprayer with 16 bars, XR11001VS nozzles and 150 L/ha volume was employed. Leaflet rust severity in R5.4 stage and grain yield were evaluated. Data were subjected to analysis of variance, and means were compared according to Tukey’s test. At eight-day intervals (six sprayings), control ranged from 75% to 93%; at 12-day intervals (four sprayings), it ranged from 35 to 63%, and at 16-day intervals (three sprayings), control ranged from 15 to 29% according to the sprayed levels. The longer the interval between applications, the lower the response of the used level for rust control and soybean grain yield. Chlorothalonil showed fungitoxicity to integrate a program of anti-resistance strategies to control soybean rust.

摘要 本试验于2017/2018年度大豆生育期在田间开展，供试大豆品种为Syn 1561 IPRO，旨在评价百菌清（chlorothalonil）施用量与施药间隔期对由豆薯层锈菌（Phakopsora pachyrhizi）引发的亚洲大豆锈病的防治效果。首次杀菌剂施药于大豆V8生育期进行，此时距大豆出苗44天，小叶锈病发病率为1.85%。本试验采用两因素因子设计，设置5个百菌清施用量梯度（1.0、1.5、2.0、2.5、3.0 L/ha），搭配8、12、16天三种施药间隔周期，采用随机区组设计并设置4次重复。试验使用配备16个喷杆、XR11001VS型喷头的自走式喷雾机，施药液量为150 L/ha。分别于大豆R5.4生育期调查小叶锈病病情严重度，并测定大豆籽粒产量。对试验数据进行方差分析，采用Tukey检验进行均值多重比较。结果显示：施药间隔为8天（共施药6次）时，防治效果介于75%~93%；施药间隔为12天（共施药4次）时，防治效果介于35%~63%；施药间隔为16天（共施药3次）时，防治效果介于15%~29%，且同一间隔期下防治效果随施用量提升而升高。施药间隔期越长，对应施用量在锈病防治与大豆籽粒产量提升方面的效应越弱。百菌清具备抑菌活性，可纳入大豆锈病防治的抗药性治理策略体系。