Acta Agriculturae Zhejiangensis ›› 2021, Vol. 33 ›› Issue (6): 1035-1041.DOI: 10.3969/j.issn.1004-1524.2021.06.08

• Plant Protection • Previous Articles     Next Articles

Determination of larval instars of Spodoptera exigua (Hübner)

ZHANG Jinming1(), ZHOU Shuxing1, LIN Ya2, LIU Min1, WANG Likun1, LYU Yaobin1,2,*()   

  1. 1. Institute of Plant Protection and Microbiology, Zhejiang Academy of Agricultural Sciences, Hangzhou 310021, China
    2. College of Chemistry and Life Sciences, Zhejiang Normal University, Jinhua 321004, China
  • Received:2021-01-18 Online:2021-06-25 Published:2021-06-25
  • Contact: LYU Yaobin

Abstract:

Spodoptera exigua(Hübner) (Lepidoptera: Noctuidae) is a serious pest of various crops, such as asparagus, tomato, cotton, radish, corn and so on. Its damaging range is very broad in China, therefore, it is necessary to determine the larval instars, which is an important evidence for forecasting and proper control of this pest. The number of larval instars was determined and tested based on frequency distribution analysis, Dyar’s rule and Crosby’s growth rule after measuring three indexes including head capsule width, body length and body weight. It was found that the range of head capsule width from the 1st to the 5th instar of S. exigua was 0.21-0.30, 0.40-0.49, 0.65-0.75, 1.05-1.15, 1.65-1.80 mm, respectively, and frequency distribution analysis showed five obvious concentration areas. The range of body length from the 1st to the 5th instar of S. exigua was 1.0-3.1, 2.5-6.5, 4.0-10.0, 5.0-15.0, 11.0-27.0 mm, respectively, which exhibited no obvious concentration areas. The range of body weight from the 1st to the 5th instar of S. exigua was 0.025-0.567, 0.200-6.000, 1.100-15.200, 6.200-65.600, 32.900-275.200 mg, respectively. These results indicated that there were 5 instars for S. exigua under the experiment conditions, and the head capsule width could be applied to the identification of larval instars rather than the body length and body weight due to the overlap among instars.

Key words: Spodoptera exigua(Hübner), larval instar, head capsule width, body length, body weight

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