卵表化合物对桔小实蝇产卵行为的影响

多种实蝇科害虫产卵后可释放寄主标记信息素来表明寄主果实已经被占据，从而调节自身或同种个体间的对寄主果实的产卵选择行为。为探明桔小实蝇卵表化合物的寄主标记作用，本文测定了桔小实蝇卵表甲醇提取物对桔小实蝇的产卵驱避活性，并观察了甲醇提取物处理对桔小实蝇产卵行为过程的影响。结果表明：桔小实蝇卵表甲醇提取物对桔小实蝇有明显的产卵驱避活性，且活性随浓度的增加而增强，当提取物浓度为100 mg/mL（虫卵与溶剂质量体积比，m/v）时，在选择性条件下的产卵驱避率为55-45%；非选择性条件下的产卵驱避率达到64%-79%。经卵表提取物处理后，桔小实蝇在寄主果实上的访问次数、试探产卵时间、试探产卵次数、实际产卵次数和产卵量均显著少于对照。证实了桔小实蝇卵表化合物具有明显的产卵寄主标记作用。     

芦荟提取物对桔小实蝇产卵驱避活性研究

【目的】研究库拉索芦荟Aloe vera L.提取物对桔小实蝇Bactrocera dorsalis Hendel的产卵驱避活性,筛选出对桔小实蝇有效的产卵调节剂。【方法】采用甲醇、丙酮、乙酸乙酯、二氯甲烷和石油醚5种溶剂对芦荟植物进行超声波提取,对5种提取物进行产卵驱避活性测定,确定产卵驱避活性较高的提取溶剂。进一步采用非选择性与选择性试验测定其对桔小实蝇产卵驱避活性的剂量效应,并对该提取物的持效期进行测定。【结果】发现5种芦荟取物对桔小实蝇均有一定的产卵驱避活性,而其中驱避活性最高的为丙酮提取物。通过选择性试验与非选择性试验发现丙酮提取物的产卵驱避率随提取物浓度的增加而增加,粗提物含量为10mg/mL时产卵驱避活性最强,分别为68.81%和89.43%。随着时间的增加,丙酮提取物的驱避活性逐渐下降,至第5天时产卵孔数与溶剂对照无显著差异,至第6天时产卵量与溶剂对照无显著差异。【结论】芦荟丙酮提取物对桔小实蝇有较高的产卵驱避活性,在植物源驱避剂方面具有一定开发前景,但持效期较短,可通过剂型改良来提高应用效率。     

植物精油对草菇双额岩小粪蝇的产卵驱避效果及毒力测定

在室内采用选择性试验测定了14种植物精油单组分化合物对草菇双额岩小粪蝇Bifronsina bifrons(Stenhammar)的产卵驱避效果及在室外采用非选择试验测定了其中3种化合物的产卵驱避效果及毒力测定。结果表明:各精油浓度为10 000 mg/L时,α-松油醇、丁香酚和茴香醛表现出明显的产卵驱避效果,其选择性产卵驱避率分别是60.17%±9.57%、51.07%±2.63%和47.66%±7.10%,产卵量均显著低于对照;月桂烯、α-蒎烯、β-蒎烯和异松油烯产卵驱避作用效果不明显。α-松油醇、丁香酚和茴香醛对双额岩小粪蝇幼虫均具有一定的毒性,对幼虫的校正死亡率分别是5.11%±3.54%、42.68%±3.94%和14.47%±6.92%;丁香酚对双额岩小粪蝇幼虫的毒力最大,LC_(50)为16 965.159 mg/L。其次是茴香醛,LC_(50)为311 941.332 mg/L。α-松油醇毒力最差,LC_(50)为40 676 080.550 mg/L。进一步非选择性试验结果表明α-松油醇(1 250 mg/L～20 000 mg/L)、丁香酚(625 mg/L～20 000 mg/L)和茴香醛(2 500 mg/L～20 000 mg/L)对双额岩小粪蝇具有明显的产卵驱避效果,驱避效果随施用浓度的增加而显著增加。在浓度为20 000 mg/L时α-松油醇、丁香酚和茴香醛的非选择性产卵驱避率分别为69.75%±3.98%、60.75%±1.94%和57.23%±3.38%。本研究为草菇生产中双额岩小粪蝇的无公害防治及高效环保的植物源驱避剂的开发提供参考。     

植物精油对荔枝蒂蛀虫的产卵驱避效果

在室内采用非选择性和选择性两种试验方法,测定了14种非寄主植物精油对荔枝蒂蛀虫的产卵驱避效果.结果表明,香紫苏油、肉桂油和香茅油对荔枝蒂蛀虫有很好的产卵驱避效果,其非选择性产卵驱避率(ODRn)达90%以上;而选择性产卵驱避率(ODR.)达80%以上.留兰香油对荔枝蒂蛀虫也有较好的产卵驱避效果,其ODRn和ODR.分别为89.19%和73.30%.     

香茅醛缩醛类化合物的合成及其对小黄家蚁的驱避活性

【目的】香茅醛类化合物具有较好的蚂蚁驱避活性,本研究旨在筛选具有良好驱避活性的新的萜类蚂蚁驱避剂。【方法】以香茅醛为原料合成了香茅醛二甲缩醛、香茅醛二乙缩醛、香茅醛二正丙缩醛、香茅醛二异丁缩醛、香茅醛乙二缩醛、香茅醛1,2-丙二缩醛和香茅醛1,3-丙二缩醛等化合物。所得产品经纯化后,用IR, MS, ¹H NMR及¹³C NMR进行结构表征,并在不同浓度下对小黄家蚁Monomorium pharaonis进行驱避活性测试。【结果】各化合物对小黄家蚁具有一定的驱避活性：在10 mg/mL的浓度下,除香茅醛二甲缩醛以外,其他化合物的驱避率均达到70%以上,其中香茅醛二乙缩醛、香茅醛乙二缩醛和香茅醛1,3-丙二缩醛对小黄家蚁的驱避率分别为87.47%,100%和97.53%。浓度为2.5 mg/mL时,其中5个化合物的驱避效果明显下降,但香茅醛乙二缩醛和香茅醛1,3-丙二缩醛仍然表现出很好的驱避活性,驱避率分别为85.33%和97.10%。方差分析也表明,香茅醛1,3-丙二缩醛在同一浓度下驱避效果最佳,其次是香茅醛乙二缩醛。【结论】结果说明,香茅醛二乙缩醛、香茅醛乙二缩醛和香茅醛1,3 丙二缩醛可以用作小黄家蚁驱避剂,而香茅醛乙二缩醛和香茅醛1,3-丙二缩醛可以达到更好的驱避效果,使用浓度为2.5 mg/mL即可。本研究为良好萜类蚂蚁驱避剂的筛选提供了参考依据。     

山胡椒及其挥发物对马铃薯块茎蛾产卵选择的影响

【目的】为了确定山胡椒Lindera glauca(Sieb.Zuce)是否对马铃薯块茎蛾Phthorimaea operculella Zeller的产卵有驱避作用。【方法】利用选择性产卵试验方法在室内分别测定了山胡椒的完整果实、压碎果实、根以及不同浓度(0.25~4.0 g E/m L)的压碎山胡椒果实正己烷提取物对马铃薯块茎蛾产卵选择性的影响;在模拟仓库内测定了压碎的果实对其产卵的影响;进而在室内测定了柠檬醛、沉香醇、香叶醇和α-水芹烯不同浓度(0.00075~0.012 g/L)的溶液对其产卵选择性的影响。【结果】山胡椒完整果实、压碎果实、根在室内对马铃薯块茎蛾产卵具有驱避效果,其中压碎果实的产卵驱避效果最好,20 g压碎果实的产卵驱避率可达93.7%。山胡椒压碎果实正己烷提取物在0.5~4.0 g E/m L的浓度范围内随着浓度的升高,产卵驱避效果逐渐增强。在模拟仓库内20 g压碎的果实产卵驱避率是82.5%;0.003~0.012 g/L的柠檬醛,0.012 g/L沉香醇,0.00075~0.012 g/L的香叶醇,0.003~0.012 g/L的α-水芹烯对马铃薯块茎蛾产卵有显著的驱避效果。【结论】山胡椒及其挥发物对马铃薯块茎蛾产卵有驱避效果。     

假臭草花精油的化学组成及对柑橘木虱的驱避和致死活性

【目的】为了让入侵植物假臭草Praxelis clematidea(Griseb)R.M.KingH.Rob.变废为宝,首次探讨了假臭草花精油对柑橘木虱Diaphorina citri Kuwayama的驱避和致死活性,以用于生物防治。【方法】采用水蒸气蒸馏法提取了假臭草不同部位的精油,并通过气相色谱-质谱联用仪(GC-MS)分析花精油的化学成分,并检测了其对柑橘木虱的生物活性。【结果】假臭草花精油得率(0.31±0.03)%高于茎叶精油的得率(0.23±0.02)%;GC-MS检测显示,假臭草花精油至少含有25种化合物,其中β-荜澄茄油烯(43.85%)和β-石竹烯(30.34%)是其主要成分;花精油浓度为40和50μL·mL~(-1)处理30 min时,对柑橘木虱的驱避反应率均可达到100%。不同浓度的花精油对柑橘木虱具有明显的致死活性。当浓度为50μL·mL~(-1)的时候,浸液法处理九里香Murraya exotica L.嫩梢18 h时,柑橘木虱校正死亡率分别达到(56.25±4.79)%,LC50值为44.83μL·mL~(-1),而熏蒸法48 h时的柑橘木虱校正死亡率仅为(66.33±5.00)%,LC50为24.80μL·mL~(-1)。假臭草花精油对柑橘木虱的驱避和致死活性可能与其主要成分的作用有关。【结论】研究结果证明假臭草花精油对柑橘木虱具有良好的驱避和致死活性,具有开发成为柑橘木虱驱避剂及杀虫剂的良好潜能。     

4种植物精油对金银花贮藏期害虫锯谷盗的生物活性北大核心CSCD

采用滤纸药膜法和广口瓶熏蒸法,在室内测定了大蒜、生姜、花椒和八角茴香4种植物精油对金银花贮藏期害虫锯谷盗的生物活性。结果表明,4种植物精油对锯谷盗成虫均具有一定的驱避活性和熏蒸活性,平均驱避率分别为70.71%、60.64%、53.78%和66.33%,平均校正死亡率分别为60.47%、51.71%、47.01%和56.28%,差异达显著水平。4种植物精油的不同浓度和不同作用时间对锯谷盗成虫的驱避活性有显著差异,随着植物精油浓度的降低和作用时间的延长,各植物精油的驱避活性逐渐降低,浓度和时间的交互作用对驱避活性无显著影响。4种植物精油的浓度、不同作用时间以及它们的交互作用对锯谷盗成虫的熏蒸活性有显著影响,随着植物精油浓度的降低,熏蒸活性逐渐降低,随着作用时间的延长,熏蒸活性逐渐增强。进一步的毒力分析表明,大蒜精油的毒力最强,12 h的LC50值为6.01μL/L,随时间的延长,各植物精油的熏蒸毒力明显增强。这说明4种植物的精油对金银花贮藏贮藏期害虫锯谷盗具有一定的生物活性,具有开发为新型无公害杀虫剂的潜力。     

小菜蛾成虫对健康和机械损伤薄荷的嗅觉反应

【目的】比较健康和机械损伤的薄荷Mentha spicata对小菜蛾Plutella xylostella成虫嗅觉反应的影响,为筛选小菜蛾植物源驱避剂提供科学依据。【方法】利用触角电位(EAG)仪和Y型嗅觉仪分别测定小菜蛾雌、雄成虫对健康和机械损伤薄荷的触角电位和嗅觉行为反应,通过田间试验测定雌蛾产卵选择的忌避反应。【结果】健康薄荷和机械损伤薄荷均能引起小菜蛾雌、雄成虫触角电位反应,但损伤薄荷引起的触角电位反应值显著高于健康薄荷(P0.05);室内行为选择试验结果显示,损伤薄荷对小菜蛾雄性成虫有显著驱避作用(P0.05),驱避指数为53.33%,对雌性成虫有极显著驱避作用(P0.01),驱避指数达到80%;田间产卵选择试验发现,损伤薄荷对小菜蛾雌成虫产卵有极显著驱避作用(P0.01),产卵忌避指数达到71.32%。但是健康薄荷对小菜蛾雌、雄成虫的行为选择和雌性成虫的产卵选择均无显著驱避作用(P0.05)。【结论】机械损伤薄荷对小菜蛾成虫有较强的驱避效果,可以对其进行驱避活性挥发物质的筛选或作为驱避源来防治小菜蛾的危害。     

4种植物精油对金银花贮藏期害虫锯谷盗的生物活性

采用滤纸药膜法和广口瓶熏蒸法,在室内测定了大蒜、生姜、花椒和八角茴香4种植物精油对金银花贮藏期害虫锯谷盗的生物活性。结果表明,4种植物精油对锯谷盗成虫均具有一定的驱避活性和熏蒸活性,平均驱避率分别为70.71%、60.64%、53.78%和66.33%,平均校正死亡率分别为60.47%、51.71%、47.01%和56.28%,差异达显著水平。4种植物精油的不同浓度和不同作用时间对锯谷盗成虫的驱避活性有显著差异,随着植物精油浓度的降低和作用时间的延长,各植物精油的驱避活性逐渐降低,浓度和时间的交互作用对驱避活性无显著影响。4种植物精油的浓度、不同作用时间以及它们的交互作用对锯谷盗成虫的熏蒸活性有显著影响,随着植物精油浓度的降低,熏蒸活性逐渐降低,随着作用时间的延长,熏蒸活性逐渐增强。进一步的毒力分析表明,大蒜精油的毒力最强,12 h的LC50值为6.01μL/L,随时间的延长,各植物精油的熏蒸毒力明显增强。这说明4种植物的精油对金银花贮藏贮藏期害虫锯谷盗具有一定的生物活性,具有开发为新型无公害杀虫剂的潜力。     

Susceptibility of the bruchid Callosobruchus maculatus (Coleoptera: Bruchidae) and its parasitoid Dinarmus basalis (Hymenoptera: Pteromalidae) to three essential oils

The bruchid Callosobruchus maculatus (F.) causes major losses during the storage of seeds of Vigna unguiculata (Walp.) in West Africa. An endemic parasitoid, the pteromalid Dinarmus basalis (Rond.) reduces the increase in bruchid populations in stores and could be used for biological control. African farmers often introduce essential oils into granaries at harvest time. In Togo, essential oils were extracted from two Gramineae, Cymbopogon nardus (L.) and Cymbopogon schoenanthus (L.) and from a Lamiaceae, Ocimum basilicum (L.). The major components of these essential oils were citronellal in C. nardus, carene-2 and piperitone in C. schoenanthus and estragol in O. basilicum. Cymbopogon schoenanthus was the most toxic oil for C. maculatus adults. D. basalis adults were more susceptible to the three essential oils than the adults of their hosts C. maculatus. In the presence of cowpea seeds, the LC50s of the three essential oils were lower than in their absence, suggesting that the seeds may absorb a part of the volatiles. High doses of three essential oils slightly affected the survival of the fourth instar or the pupae of C. maculatus. This high survival was due to protection of larvae from volatiles by the surrounding seeds. The D. basalis were more affected by the oil volatiles than their hosts. Sub-lethal doses of essential oils reduced the duration of the adult life of both insect species and fecundity of the females. The differences in sensitivity of the host and its parasitoid could influence their population dynamics. The introduction of the essential oils into storage systems potentially could reduce density of parasitoid populations and increase seed losses.     

Fungal Pathogens Associated with Banana Fruit in Sri Lanka,and their Treatment with Essential Oils

The crown rot pathogens isolated from banana samples collected from 12 localities in Sri Lanka were Lasiodiplodia theobromae, Fusarium proliferatum and Colletotrichum musae. Fungal pathogens isolated were able to cause crown rot disease alone or in combination. Disease severity was higher when combinations of virulent pathogens were used. Cymbopogon nardus and Ocimum basilicum oils displayed fungicidal activity against C. musae and F. proliferatum between 0.2-0.6% (v/v) in a Poisoned food bioassay. Slightly lower concentrations of the test oils were needed for similar activity during liquid bioassays. The combination of Cymbopogon nardus and O. basilicum oils demonstrated synergistic action during both in-vivo bioassays.     

矿物油乳剂拒避橘小实蝇的有效组分分析

高品质的矿物油乳剂可用于有机食品生产,在害虫综合治理中有良好的应用前景。矿物油是包含多种化学成分的混合物,其组成成分和比例决定其理化性质并关系到其防治病虫害的效果。已有研究报道表明,矿物油乳剂对许多害虫有拒避作用,但其机理及相关性组成成分尚未研究清楚。本实验测定了4种矿物油乳剂即SK绿颖农用喷洒油、加德士-路易夏用油、安波尔喷洒油、法夏乐石蜡油（分别简称为SK,Caltex,Ampol和Citrole油）和Caltex油＜120℃,＞120℃,＜105℃,105~120℃及SK油＜110℃、＞110℃等6种分子蒸馏组分的正构烷烃碳数当量nCy值、碳数分布值及其对橘小实蝇Bactrocera dorsalis的产卵拒避效果。室内生物测定结果显示,橘小实蝇在SK,Caltex,Ampol和Citrole油0.5%水乳液及清水浸蘸处理后的香蕉上平均产卵孔数分别为17.850±1.282,3.400±0.630,15.850±1.439,20.650±1.212和19.050±1.155,在同样方法处理的阳桃上平均产卵孔数分别为15.500±3.969,3.000±0.707,13.750±4.131,17.250±4.385和62.000±4.708。橘小实蝇在6种分子蒸馏组分0.5%水乳液处理后的香蕉上的平均产卵孔数分别为4.400±1.166,8.200±0.583,5.400±1.720,2.400±1.077,4.800±1.594和12.200±2.63,显示不同矿物油的拒避效果差异显著（P<0.05）,拒避效果最好的矿物油的正构烷烃碳数当量nCy值在nC23左右.矿物油对橘小实蝇的产卵拒避效果与其相应的碳数分布值的Spearman等级相关性分析显示,其拒避效果与矿物油中的C23组分的含量呈显著正相关关系（P<0.05）。这可为进一步分析矿物油乳剂拒避害虫的作用成分和探索其机理提供参考。     

Insecticidal and biological efficacy of two vegetable oils against Callosobruchus maculatus (Fabricius) (Coleoptera: Bruchidae) under laboratory conditions

Bioefficacy of two vegetable oils, namely ethyl oleate and Acorus calamus, were conducted against the pulse beetle Callosobruchus maculatus (Fabr.) under a constant temperature of 29 ± 1 °C and a relative humidity of 65 ± 5% R.H. Four concentrations (0.125, 0.25, 0.5 and 1.0%) of each oil were used against the adult and tested their latent effect on the immature stages of the beetle. The results obtained show insecticidal effect of both ethyl oleate and A. calamus oil; however, A. calamus oil proved to be more toxic to the adults at all the concentrations tested in comparison to the ethyl oleate oil. As the concentration of the oils decreased, the percentage mortality decreased. The obtained results concentrated on biological efficacy of the oils tested against the adults. Both oils affected the longevities of both male and female C. maculatus adults in comparison to the control. The oviposition periods of the adult female were affected significantly in comparison to the control. A. calamus oil prohibited oviposition completely at high concentrations of 0.5 and 1.0% and caused complete sterility to the females. Lower concentrations decreased the oviposition period greatly and reduced the number of eggs laid in comparison to the control. Ethyl oleate had an inconsiderable latent effect on the incubation period as well as the percentage of hatching of the resulting eggs. A. calamus oil decreased the percentage of egg hatchability with serious increase in the percent sterility. The two tested oils had slight extension in either larval or pupal stage of the resulting progeny of C. maculatus. Both oils show oviposition deterrency towards C. maculatus adults. The oviposition deterrent index was 100% when mung bean seeds were treated with A. calamus oil. The bruchid females laid all eggs on control seeds and no eggs were laid on treated seeds.     

Effects of Cymbopogon nardus (L.) W. Watson essential oil on the growth and morphogenesis of Aspergillus niger

The growth inhibitory effect of Cymbopogon nardus (L.) W. Watson var. nurdus essential oil on Aspergillus niger (Van Tieghem) mycelium was determined on agar medium. The mycelium growth was completely inhibited at 800 mg/L. This concentration was found to be lethal under the test conditions. Essential oil at 400 mg/L caused growth inhibition of 80% after 4 days of incubation, and a delay in conidiation of 4 days compared with the control. Microscopic observations were carried out to determine the ultrastructural modifications of A. niger hyphae after treatment with C. nardus essential oil. The main change observed by transmission electron microscopy concerned the hyphal diameter and the hyphal wall, which appeared markedly thinner. These modifications in cytological structure might be caused by the interference of the essential oil with the enzymes responsible for wall synthesis which disturb normal growth. Moreover, the essential oil caused plasma membrane disruption and mitochondrial structure disorganization. The findings thus indicate the possibility of exploiting Cymbopogon nardus essential oil as an effective inhibitor of biodegrading and storage-contaminating fungi.     

矿物油乳剂作用下橘小实蝇的产卵拒避及触角电位反应

为了研究矿物油乳剂对害虫行为的干扰作用,测定和比较了4种矿物油乳剂对橘小实蝇Bactrocera dorsalis (Hendel)的产卵拒避效果及在其作用下该虫的触角电位反应（EAG）,并测试了其中拒避效果最好的Caltex Lovis夏用油的不同施用方式（浸蘸法和喷雾法）及不同施用浓度（150,250,350,450倍液）对橘小实蝇产卵拒避的影响。结果显示：分别用4种矿物油乳剂200倍液以浸蘸法处理香蕉,仅Caltex Lovis夏用油处理对橘小实蝇产卵拒避效果显著,其平均产卵孔数仅为清水对照的15.14%;其他3种矿物油乳剂则没有明显效果。这表明矿物油乳剂对昆虫行为的干扰作用与其组成成分相关。4种矿物油乳剂对橘小实蝇的产卵拒避效果与各矿物油乳剂的50倍液滴于滤纸条后0.5 h的雌成虫EAG值间无显著相关性,但与滴于滤纸条后3 h（滤纸条上水分已蒸发）的EAG值间有显著的负相关性,说明矿物油乳剂的挥发性组分对橘小实蝇的产卵拒避影响不大,因此推测矿物油乳剂在植物表面形成的油膜对植物挥发性物质的封闭作用与其产卵拒避效果可能有一定的关系。浸蘸法不同浓度处理间的产卵拒避效果无显著差异,均明显高于喷雾法处理及清水对照。在喷雾法处理中,仅150倍液有显著产卵拒避效果。这说明,矿物油乳剂需要在植物表面达到一定的沉积量,才能对橘小实蝇有较好的产卵拒避作用。与喷雾法相比,浸蘸法可能较利于矿物油在植物表面的沉积,这也佐证了矿物油乳剂所形成油膜的封闭性与其产卵拒避效果有一定的关系。     

Toxic and deterrent effects of two volatile oils against cowpea weevil,Callosobruchus chinensis (Coleoptera: Bruchidae)

The fumigant effect of Mentha piperita and Ocimum basilicum oils and their mixture against adults and eggs of Callosobruchus chinensis (L.) was evaluated. Bioassay experiments showed that Ocimum basilicum oil was significantly effective against adult and egg stage which was the least effective. However, in the fumigant toxicity experiments against adult stage, Ocimum basilicum oil at a dose of 1.0 μl/38.5 ml air caused 100% mortality (LC₅₀ = 1.88), the mixture of both oils at a dose of 6.0 μl/38.5 ml air caused 100% mortality (LC₅₀ = 10.3) and Mentha piperita oil at a dose of 80.0 μl/38.5 ml air caused 80.0% mortality (LC₅₀ = 41.224) during a one day exposure period. Regarding the oviposition deterrent activity, Ocimum basilicum oil achieved 100% oviposition deterrent (at a dose of 0.5 μl/38.5 ml air) followed by the mixture of Mentha piperita and Ocimum basilicum oils, which achieved 71.22% oviposition deterrent (at a dose of 1.0 μl/38.5 ml air) and Mentha piperita oil, which achieved 39.6% oviposition deterrent (at a dose of 5.0 μl/38.5 ml air). The essential oils and their mixtures studied here determined a significant decrease in the number of eggs hatched and in the emergence of adults. The eggs failed to hatch on using Ocimum basilicum oil at a dose of 0.6 μl/38.5 ml air. However, the number of eggs hatched decreased to 7.4 on using a mixture of oils at a dose of 2.0 μl/38.5 ml air and 14.0 with Mentha piperita oil at a dose of 80.0 μl/38.5 ml air compared with 25.0 eggs hatched in the control experiments. On the other hand, the percentage reduction in emerging adults were 100% for Ocimum basilicum oil, 90.9% for a mixture of the two oils and 72.7% for Mentha piperita oil. Results showed that Ocimum basilicum oil and Ocimum basilicum oils plus Mentha piperita oils in blend are potential alternatives to synthetic fumigants in the treatment of durable agricultural products. Successful adoption of plant oils in the protection of food commodities promises an eco-friendly option compatible with international biosafety regulations.     

Essential oils of citrus fruit stimulate oviposition in the Mediterranean fruit fly Ceratitis capitata (Diptera: Tephritidae)

Female Mediterranean fruit flies (medfly) Ceratitis capitata (Wiedemann) (Diptera: Tephritidae) perceive both qualitative and quantitative aspects of citrus fruit chemistry. However, the behavioural and biological adjustments of this response remain largely unknown. In the present study, the ovipositional responses of gravid female medflies to essential oils (i.e. the most critical resistance factor to medfly infestation) of various citrus fruits are investigated. In dual‐choice (treatment versus distilled water control) experiments, females lay significantly more eggs into pre‐punctured hollow oviposition hemispheres (domes) provided with 1 µL of citrus peel oil from sweet orange, satsuma mandarin, bitter orange, grapefruit and lemon compared with odourless domes. No‐choice tests show a weak effect of lemon essential oils in stimulating oviposition. The female ovipositional response to sweet orange oil (the most active in eliciting oviposition) is dose‐dependent. Additionally, limonene, the most abundant chemical in all citrus oils, stimulates oviposition, whereas linalool, a representative compound of immature citrus fruit associated with high toxicity against immature stages of fruit flies, has a significant deterrent effect. In further no‐choice tests, females lay approximately 23% fewer eggs in limonene (93%) (amount found in orange oil) and 60% fewer eggs in limonene 93% plus linalool 3% (approximately 10‐fold the amount found in orange oil) mixtures, relative to sweet orange oil. The results suggest that the limonene content accounts largely (but not completely) for the ovipositional responses observed in sweet orange oil, whereas high linalool proportions are capable of significantly masking and/or disrupting its stimulatory effects in citrus oils. The importance and practical implications of these findings with respect to understanding how citrus fruit chemistry influences the ovipositional responses of medfly is discussed.     

Evaluation of the Activity of the Essential Oil from an Ornamental Flower against Aedes aegypti: Electrophysiology,Molecular Dynamics and Behavioral Assays

Dengue fever has spread worldwide and affects millions of people every year in tropical and subtropical regions of Africa, Asia, Europe and America. Since there is no effective vaccine against the dengue virus, prevention of disease transmission depends entirely on regulating the vector (Aedes aegypti) or interrupting human-vector contact. The aim of this study was to assess the oviposition deterrent activity of essential oils of three cultivars of torch ginger (Etlingera elatior, Zingiberaceae) against the dengue mosquito. Analysis of the oils by gas chromatography (GC)—mass spectrometry revealed the presence of 43 constituents, of which α-pinene, dodecanal and n-dodecanol were the major components in all cultivars. Solutions containing 100 ppm of the oils exhibited oviposition deterrent activities against gravid Ae. aegypti females. GC analysis with electroantennographic detection indicated that the oil constituents n-decanol, 2-undecanone, undecanal, dodecanal, trans-caryophyllene, (E)-β-farnesene, α-humulene, n-dodecanol, isodaucene and dodecanoic acid were able to trigger antennal depolarization in Ae. aegypti females. Bioassays confirmed that solutions containing 50 ppm of n-dodecanol or dodecanal exhibited oviposition deterrent activities, while a solution containing the alcohol and aldehyde in admixture at concentrations representative of the oil presented an activity similar to that of the 100 ppm oil solution. Docking and molecular dynamics simulations verified that the interaction energies of the long-chain oil components and Ae. aegypti odorant binding protein 1 were quite favorable, indicating that the protein is a possible oviposition deterrent receptor in the antenna of Ae. aegypti.     

Role of foliar chemistry versus leaf-tip morphology in egg-batch placement by Chrysophtharta bimaculata (Olivier) (Coleoptera: Chrysomelidae)

Abstract The Tasmanian eucalyptus leaf beetle, Chrysophtharta bimaculata (Olivier) (Chrysomelidae: Paropsini), deposits batches of eggs on the leaf surfaces of its Eucalyptus hosts. Using a primary host of the beetle, Eucalyptus regnans , the aim of the present study was to examine whether oviposition site discrimination was occurring at the level of the individual leaf and what, if any, chemical attributes were involved in site selection. From field surveys, it was found that 55−65% of egg batches were laid in the leaf-tip zone, despite this zone representing only 5.6% of the total leaf-surface area. Chemical analyses of expanding leaves showed that the concentrations of three essential oil components and three surface waxes varied significantly between the leaf tip and remainder of the leaf. However, on plastic mimic leaves with uniform, non-foliar chemistry, eggs were still preferentially laid near 'leaf' tips. Hence, leaf essential oils and surface waxes need not be involved in oviposition site choice. Observations of ovipositing beetles showed that they wrapped their tarsi around the leaf margin, suggesting that the ability to grasp the edges of a leaf may explain the oviposition pattern observed.