Sublethal effect of insecticides on reproduction of Megalurothrips usitatus (Bagrall) (Thysanoptera: Thripidae)
Author of the article:LUO Ya-Li;SHI Dan;QIAO Xue-Ying;DAN Jian-Guo
Author's Workplace:College of Plant Protection, Hainan University, Key Laboratory of Green Prevention and Control of Tropical Plant Diseases and Pests (Hainan University), Ministry of Education, Haikou 570228, China;College of Plant Protection, Hainan University, Key Laboratory of Green Prevention and Control of Tropical Plant Diseases and Pests (Hainan University), Ministry of Education, Haikou 570228, China;College of Plant Protection, Hainan University, Key Laboratory of Green Prevention and Control of Tropical Plant Diseases and Pests (Hainan University), Ministry of Education, Haikou 570228, China;College of Plant Protection, Hainan University, Key Laboratory of Green Prevention and Control of Tropical Plant Diseases and Pests (Hainan University), Ministry of Education, Haikou 570228, China
Key Words:Megalurothrips usitatus; cyantraniliprole; amitraz; indoxacarb; sex ratio; cowpea
Abstract:
[Objectives] The aim of this paper is to explore the
sublethal effects of three insecticides on reproduction of bean flower thrips [Megalurothrips usitatus (Bagnall)], one
of the most economically important insect pests of cowpea [Vigna unguiculata (L.) Walp.] in Hainan Island, China. [Methods] Under laboratory
conditions of (26±1) ℃, 60%±5% R.H. and a photoperiod of 14L∶10D, with young leaves of
cowpea (var. Chunfeng-changjiangdou) as food of the bean flower thrips, the
lethal and sublethal concentrations of cyantraniliprole, amitraz, and indoxacarb for the
1-d-old mated adult females were determined using a leaf-disc dipping bioassay method. After 48 h
exposure to LC20 concentration of each insecticide, the surviving
mated or unmated adult females were provided with non-treated leaf discs. The
number of eggs and subsequent adult offspring were counted daily until the
parental females died. Sex ratios of adult offspring produced by mated females
were calculated as proportion of males, and then sex ratios of eggs laid by
them were estimated using survival rates of the offspring produced by both
mated females and unmated females. [Results] Exposure
to three insecticides at LC20 concentration all significantly
decreased the survival duration of
either mated or unmated females. The number of adult offspring produced by mated females
exposed to cyantraniliprole and
amitraz were also significantly
reduced. Sex ratios of adult offspring produced by mated females following
sublethal exposure to cyantraniliprole, amitraz, and indoxacarb were 0.60, 0.47, and 0.41,
respectively, which all were not significantly different from that of control. There was no significant difference in sex ratio of eggs laid by mated
females among insecticide treatments
and control. [Conclusion] Sublethal exposure to cyantraniliprole, amitraz, and indoxacarb decreases
to some extent the survival duration of the parental females of the bean flower thrips, and the number of adult
offspring produced by them, but does not significantly change their sex
allocation.