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Infection Characterization by Spodoptera frugiper ascovirus Isolate 84?36 and Growing Development of Infected Spodoptera exigua Larvae

HU Jue, GU Xingshi, LI Shunji, HUANG Guohua   

  1. Hunan Provincial Key Laboratory for Biology and Control of Plant Diseases and Insect Pests/Institute of Virology, Hunan Agricultural University/College of Plant Protection, Hunan Agricultural University, Changsha 410128, China
  • Received:2015-07-25 Online:2016-04-08 Published:2016-04-08

Abstract: Ascoviruses are double-strand DNA viruses with potential biocontrol for the insect pests. In this study, Spodoptera frugiperda ascovirus isolate 84-36 was used to inoculate the first to the fifth instar of Spodoptera exigua (Hübner) larvae by both per os (1.09×1010 copies per larva for the first to second instar larvae; 9.77×109 copies per larva for the third to fifth instar larvae) and intrahaemocoelic injection (1.56×109 copies per larva) with the titer of 9.77×1012 genomecopies/mL hemolymph. Mortality, growth and development of the inoculated larvae were observed and recorded. While the corrected mortalities of the first to the third instars inoculated per os were 18.9%±1.11%, 4.4%±1.11%, 2.2%±1.11%, respectively, the treatment showed no effects on the fourth and fifth instars. The first instars were significantly easier to be infected by the virus than the second and the third instars. Corrected mortalities of the larvae inoculated by injection in both the third and fourth instars were 100.00%, and that in the fifth instars was 80.00%±0.00%. The survival time of the diseased larvae was apparently extended. Meanwhile, food intake of the larvae inoculated in the third and the fourth instars was reduced remarkably at day 2, and the body weight remained fairly constant from day 3-postinoculation. These results reveal that the Spodoptera frugiperda ascovirus isolate 84-36 has the potential for biological control.

Key words: Spodoptera exigua, growth and development, ascoviruses, pathogenicity, mortality rate

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