The bioactivity of fused heterocyclic compounds of pyraquinil against Spodoptera frugiperda
Author of the article:HUANG Su-Qing； ZHANG Zhi-Xiang； JIANG Xun-Yuan；XU Han-Hong
Author's Workplace：College of Chemistry and Chemical Engineering, Zhongkai University of Agriculture and Engineering, Guangzhou 510225, China; State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources and Key Laboratory of Natural Pesticide and Chemical Biology, Ministry of Education, South China Agricultural University, Guangzhou 510642, China
Key Words：Spodoptera frugiperda; pyraquinil, bioassay; field efficacy
Abstract：[Objectives] Spodoptera frugiperda, an insect native to the Americas, causes significant damage to crops worldwide and has been rated one of the world's top ten plant pests by the international center for agriculture and biological sciences (CABI). S. frugiperda has now invaded more than 14 provinces in mainland China where it poses a major threat to corn and other crops. [Methods] We used the leaf immersion method and field trials to investigate the biological activity of pyraquinil against S. frugiperda larvae. [Results] The LC50 of pyraquinil after one two and three days was 5.51、1.95 and 0.91 mg/L, respectively for 2nd instar larvae, 7.50, 3.92 and 1.94 mg/L, respectively for 3rd instar larvae, and 13.79, 10.30 and 8.78 mg/L, respectively for 4th instar larvae. At the corn trumpet stage, field trial results show that by 3 d after spray treatment pyraquinil had reduced the numbers of 1st to 3rd instars by > 90%, but the reduction in numbers of 4th to 6th instar larvae was < 50%. At the corn trumpet stage, control was over 93.65% after 3 days and over 98.78% after 7 days of trumpet point treatment. [Conclusion] Pyraquinil is effective on the younger larvae of S. frugiperda, but older larvae are less susceptible because they are able to burrow into corn plants. The key window for the prevention of S. frugiperda is therefore the 1st to 3rd instar period. Pesticide application should be combined with plant and field monitoring.