Comparative soil distribution and dissipation of phoxim and thiamethoxam and their efficacy in controlling Bradysia odoriphaga Yang and Zhang in Chinese chive ecosystems |
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| Institution: | 1. Department of Entomology, China Agricultural University, Beijing 100193, China;2. Sanya Institute of China Agricultural University, Sanya 572025, China;1. Department of Crop and Soil Environmental Sciences, Virginia Polytechnic Institute, 185 Ag Quad Lane, Blacksburg, VA 24061, USA;2. Department of Applied Chemistry, China Agricultural University, No. 2 West Yuanmingyuan Road, Beijing, PR China |
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| Abstract: | Bradysia odoriphaga Yang and Zhang (the chive gnat) is the major insect pest affecting Chinese chives (Allium tuberosum Rottl. ex Spreng.) in Northern China. Only three insecticide products are registered for its control. In the present study, we compared the persistence and distribution of thiamethoxam and phoxim in soil and determined their long-acting control effects against B. odoriphaga and two other secondary pests, Thrips alliorum Priesner and the Asiatic onion leaf miner Acrolepia alliella Semenov and Kuznetsov (Lepidoptera: Acrolepiidae), after a single soil application using the directional spray-washing method during the early Chinese chive root-rearing period. Under the same applied dosage, the rhizosphere soil at a depth of 4.0–10.0 cm had concentrations of thiamethoxam and phoxim ranging from 2.21 to 7.44 mg/kg and 0.09–0.44 mg/kg, respectively, at the 7th day after application. The half-lives of thiamethoxam and phoxim in the soil were 27.5 and 6.7 days, respectively. Thiamethoxam persisted for 210 days, whereas phoxim only persisted for 45 days in the soil and plants. In addition, thiamethoxam applied at 6.0 kg a.i./ha maintained a low population density of B. odoriphaga, T. alliorum and A. alliella for nine months longer than phoxim. In conclusion, thiamethoxam may help farmers more effectively manage B. odoriphaga and other secondary pests on Chinese chive and reduce the costs of insecticide use while sustaining protection. |
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| Keywords: | Thiamethoxam Phoxim Soil distribution Dissipation Control efficacy |
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