Effect of soil moisture on the pupation and emergence of the armyworm, Mythimna separata
Author of the article:LI Li-Kun;WANG Xiao-Hui;LIU Jia-Wen;WANG Yan-Hui;CHEN Fa-Jun
Author's Workplace:Insect-Information Ecology Laboratory, Department of Entomology, College of Plant Protection, Nanjing 210095, China;Insect-Information Ecology Laboratory, Department of Entomology, College of Plant Protection, Nanjing 210095, China;Insect-Information Ecology Laboratory, Department of Entomology, College of Plant Protection, Nanjing 210095, China;Insect-Information Ecology Laboratory, Department of Entomology, College of Plant Protection, Nanjing 210095, China;Insect-Information Ecology Laboratory, Department of Entomology, College of Plant Protection, Nanjing 210095, China
Key Words: armyworm; soil moisture content; temperature and humidity; pupation; feather
Abstract:[Objectives] To study the effects of soil humidity on the pupation and emergence of the armyworm, Mythimna separata, so that local winter soil surface temperature can be used to predict its overwintering period and subsequent emergence.[Methods] The relative water content of indoor and outdoor soil samples were set as 0, 10%, 20%, 40%, 60%, 80% and 100%, respectively, and pupation and emergence rates of armyworm larvae in these samples were recorded and compared.[Results] Soil water content had significant effects on pupation, eclosion and overwintering period. (1) In soil with 0, 10%, 20%, 40%, 60%, 80% and 100% relative soil water content, the average pupation rate was 75.0%, 82.5%, 92.5%, 90.0%, 77.5%, 65.0% and 60.0%, respectively (2016-2017). Experimental results in the second year were similar; 70.0%, 75.0%, 90.0%, 87.5%, 77.5%, 60.0% and 57.5%, respectively (2017-2018). The optimal soil water content was between 20% and 40%, and water content of between 0% and 100% was not conducive to pupation. (2) Soil with water content of 0, 10%, 20%, 40%, 60%, 80% and 100% had average armyworm emergence rates of 12.5%, 47.5%, 42.5%, 47.5%, 77.5%, 45.0% and 7.5%, respectively in the first year (2016-2017) and similar results in the second year (2017-2018); 20.0%, 27.5%, 40.0%, 57.5%, 67.5%, 52.5% and 25.0%, respectively. The optimal soil water content for adult emergence was 0%, 60% and 100%. (3) Pupae were buried under the same soil moisture content treatment in outdoor fields in November 2016 and November 2017 failed to emerge. [Conclusion] The most suitable soil moisture content for the pupation of armyworms in the Dezhou city region of Shandong province is between 20%-40%, whereas the optimal soil moisture content of excavated soil is about 60%. Although the water content of soil in winter had little effect on pupae and adults, the temperature was too low for worms to overwinter. Soil moisture content can affect the emergence of pupae and adults, especially the emergence of pupae. Soil moisture content can be changed by artificial irrigation or drought to control the emergence of armyworms.