The Effect of Chemical Composition and Bioactivity of Several Essential Oils on Tenebrio molitor (Coleoptera: Tenebrionidae)

The major chemical components of four essential oils (EOs) extracted from dry leaves of Citrus limonum, Cymbopogon citratus, Litsea cubeba, and Muristica fragrans were analyzed with gas chromatograph-mass spectrometer and their fumigant, contact, and repellent activities against 10th instar and adults of Tenebrio molitor were also assayed. The results indicated that the major constituents of C. limonum and Cy. citrates were D-limonene (38.22%) and 3,7-dimethyl-6-octenal (26.21%), while which of L. cubeba and M. fragrans were (E)-3, 7-dimethyl-2, 6-octadienal (49.78%) and (E)-cinnamaldehyde (79.31%), respectively. Contact activities of L. cubeba and C. limonum with LC₅₀ values of 21.2 and 13.9 µg/cm² at 48 h and repellence activities (>89.0% repellence indexes) (P < 0.05) at 12 h on 10th instar were better than those of the other two EOs. Nevertheless, the fumigation activities of L. cubeba on 10th instar and adults (LC₅₀ = 2.7, 3.7 μl/liter) were stronger than those of C. limonum (LC₅₀ = 10.9, 12.0 μl/liter) at 96 h and significant (not overlapping confidence intervals). The EOs of L. cubeba and C. limonum have clearly elongated the growth and development of larvae, egg, and slightly shorten pupae and adults of T. molitor compared with the control. The mainly active ingredients of L. cubeba and C. limonum, including D-limonene and β-pinene, were demonstrated to coinhibit the actives of AChE and enhance the toxicities on 10th instar of T. molitor. These results indicate that the EOs of L. cubeba and C. limonum could have great potential as botanical insecticides against T. molitor.     

4���в�ҩ���̶�����������

为探明中草药提取物对仓储害虫绿豆象的生物活性,为其植物源农药的开发利用提供依据,通过点滴、熏蒸等方法测定络石、苣荬菜、土牛膝和马松子等4种中草药正己烷提取物对绿豆象的触杀、熏蒸和趋避等活性.结果表明:马松子的触杀活性最高,达83％;其次是土牛膝和苣荬菜,分别为63％和57％.4种中草药均没有明显的熏蒸活性,苣荬菜和土牛膝的趋避活性分别为Ⅲ级和Ⅱ级.中草药不同部位提取物的杀虫效果存在差异,络石的触杀效果叶优于藤(56.7％＞13.3％),苣荬菜的触杀活性茎优于叶(60％＞53.3％),但是,其趋避活性叶优于茎(56.7％＞16.7％).     

Chemical Composition and Bioactivity of Lippia adoensis Hochst ex. Walp (Verneneaceae) Leaf Essential Oil Against Callosobruchus maculatus Fabricius (Coleoptera：Chrysomelidae)

Essential oil(EO) of Nigeria-grown Lippia adoensis leaf was analyzed using gas chromatography mass spectrometry(GCMS) and its fumigant and repellent properties against Callosobruchus maculatus were evaluated. Sixteen compounds predominated by monoterpenes were identified. The major compounds were Eucalyptol(28.36%), α-Terpineol(25.99%), γ-Terpinene(15.24%), α-Pinene(5.08%), 1H-Cyclopropa[a]naphthalene(4.25%) and 1, 3, 6, 10-Dodecatetraene(3.74%). Percentage mortality due to fumigant toxicity was dose- and exposure period-dependent. One hour after treatment(HAT), application of L. adoensis leaf EO at 107 μL· L~(-1) air caused significantly(p?0.05) higher mortality(50.00%) than 0.00% mortality observed at 0-53 μL· L~(-1) air, but not significantly(p?0.05) different from 22.50% observed in 80 μL· L~(-1) air. At 3 HAT, application of L. adoensis EO at 80 μL· L~(-1)air caused significantly higher mortality(90.00 %) than mortality observed at 0 μL· L~(-1) air. At 6 HAT, application of L. adoensis EO at 53-107 μL· L~(-1) air caused significantly higher mortality(100.00 %) than that was observed in the control. The same trend was observed at 12 HAT where 100 % mortality observed in 27-107 μL· L~(-1) air was significantly greater than 13.33 % observed in the control. At 3 HAT, percentage repellence was significantly(p0.05) affected by doses. Application of EO at 10-30 μL· cm~(-2) caused class V repellence(86.67%-100%) compared with the control which caused class I repellence(0-20%).     

Fumigant toxicity of<Emphasis Type="Italic">Eucalyptus blakelyi</Emphasis> and<Emphasis Type="Italic">Melaleuca fulgens</Emphasis> essential oils and 1,8-cineole against different development stages of the rice weevil<Emphasis Type="Italic">Sitophilus oryzae</Emphasis>

Essential oils extracted fromEucalyptus blakelyi (1,8-cineole, 77.5%),Melaleuca fulgens (1,8-cineole, 56.9%) and 1,8-cineole were shown to have fumigant toxicity against different development stages ofSitophilus oryzae. The eggs ofS. oryzae were the most tolerant, followed by pupae, larvae and adults in that order.M. fulgens oil,E. blakelyi oil and 1,8-cineole at 100 μl per liter of air gave, respectively, LT₅₀ values of 16.2, 17.4 and 9.1 h for adults, 31.1, 19.3 and 17.5 h for larvae, 55.6, 75.2 and 39.7 h for pupae, and required >7 days for eggs. Only 1,8-cineole (200 μl ⁻¹ air) gave a significant egg kill by 7 days and the LT₉₅ was 134.5 h. 1,8-Cineole could be a useful new fumigant. http://www.phytoparasitica.org posting Oct. 3, 2004.     

Influence of temperature on toxicity of propylene oxide at low pressure against<Emphasis Type="Italic">Tribolium castaneum</Emphasis>

Toxicity of propylene oxide (PPO) at low pressure against the most common stored-product insect,Tribolium castaneum (Herbst), over a short exposure time, was tested at three different temperatures (16°, 22° and 30°C). Toxicities of PPO at 100 mm Hg were strongly influenced by ambient temperature. LD₅₀ and LD₉₉ toxicities ranged from 4.7 to 28.9 mgl ⁻¹ and from 10.5 to 72.6 mgl ⁻¹ respectively, showing that susceptibility was positively correlated to the temperature. The LD₉₉ values for all life stages (except the larval stage) were significantly lower at 30° than those at 16° and 22°C. However, the LD₉₉ values for all life stages (except the pupal stage) at 16° were not significantly different from those at 22°C. A concentration × time (Ct) product of 291, 171 and 98 mg h/l was required to obtain complete mortality (99%) ofT. castaneum at 16°, 22° and 30°C, respectively. Thus, the efficacy of PPO at 100 mm Hg to all life stages ofT. castaneum also decreased as the temperature decreased from 30° to 16°C. http://www.phytoparasitica.org posting Sept. 28, 2004.