Activity of Ten Fungicides against Phytophthora capsici Isolates Resistant to Metalaxyl |
| |
Authors: | Rende Qi Tao Wang Wei Zhao Ping Li Jiancheng Ding Zhimou Gao |
| |
Institution: | 1. Institute of Plant Protection and Agro‐products Safety, Anhui Academy of Agricultural Sciences, , Hefei, 230031 China;2. Scientific Observing and Experimental Station of Crop Pests in Hefei, Ministry of Agriculture, , Hefei, 230031 China;3. College of Plant Protection, Anhui Agricultural University, , Hefei, 230036 China |
| |
Abstract: | Pepper Phytophthora blight (PPB), caused by Phytophthora capsici, is an important disease of pepper in China. The extensive application of metalaxyl has resulted in widespread resistance to this fungicide in field. This study has evaluated the activities of several fungicides against the mycelial growth and sporangium germination of metalaxyl‐sensitive and metalaxyl‐resistant P. capsici isolates by determination of EC50 values. The results showed that the novel carboxylic acid amide (CAA) fungicide mandipropamid exhibited excellent inhibitory activity against PPB both in vitro and in vivo, with averagely EC50 values of 0.075 and 0.004 μg/ml in mycelial growth and sporangium germination, respectively, and over 88% efficacy in controlling PPB. The other three CAA fungicides also provided over 70% efficacy in controlling PPB. The mycelial growth was less sensitive to quinone outside inhibitor (QoI) fungicides azoxystrobin and trifloxystrobin than that of sporangium germination in P. capsici isolates. However, azoxystrobin and trifloxystrobin provided over 80% efficacy in controlling PPB. It was noted that propamocarb and cymoxanil did not exhibit activity against the mycelial growth or sporangium germination of P. capsici isolates in the in vitro tests, with over 70% efficacy in controlling PPB. The new fungicide mixture 62.5 g/l fluopicolide + 625 g/l propamocarb (trade name infinito, 687.5 g/l suspension concentrate (SC)) produced over 88% efficacy in controlling PPB caused by both metalaxyl‐sensitive and metalaxyl‐resistant isolates. The data of this study also proved that there was obviously no cross‐resistance between metalaxyl and the other tested fungicides. Therefore, these fungicides should be good alternatives to metalaxyl for the control of PPB and management of metalaxyl resistance. |
| |
Keywords: | carboxylic acid amides
Phytophthora capsici
metalaxyl resistance management quinone outside inhibitor fungicides disease control |
|
|