Sublethal effects of pyriproxyfen,a juvenile hormone analogue,on Plutella xylostella (Lepidoptera: Plutellidae): life table study

The sublethal effects of pyriproxyfen (PYR, a juvenile hormone analogue) were investigated for two consecutive generations on life-history parameters, such as developmental time, pupal weight, fecundity, fertility and longevity of the diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae). After topical application bioassay of third instar larvae, the LC₂₅ and LC₅₀ values (as sublethal doses) were determined to be 1.49 and 2.01 μg/μl, respectively. The results showed that the egg incubation period, larval and pupal duration times and oviposition period were increased in treated groups compared with the control (treated with distilled water). Pupal weight, adult longevity, fecundity and fertility were significantly reduced in the treatment groups compared with the control. Using the age-stage, two-sex life table analysis, we found that the intrinsic rate of increase (r), finite rate of increase (λ), gross reproduction rate (GRR) and net reproductive rate (R ₀) significantly decreased while the mean generation time (T) and doubling time (DT) increased in two treatment groups compared with the control. In addition, administration of PYR induced morphogenetic abnormalities including untanned pupae, larval–pupal intermediates and various defective adults. The LC₅₀ value was more effective on all of the above biological characteristics than the LC₂₅ for both generations, although parents were more affected than the offspring. In general, our results revealed that PYR was highly effective against P. xylostella in the laboratory both directly (causing mortality) and indirectly (disruption of normal growth and development). We conclude that PYR is an excellent candidate for suppressing populations of P. xylostella through its sublethal effects.     

Effect of temperature on development rate and intrinsic rate of increase ofAphis gossypii reared on greenhouse cucumbers

Thermal requirements for development and life table statistics ofAphis gossypii Glover (Homoptera, Aphididae) were determined over a range of constant temperatures from 10 to 30°C. The lower development threshold and the sum of effective temperatures were 6.9°C and 90.1°C, respectively, for preimaginal development, and 5.8°C and 113.6°C from birth to the onset of reproduction. Mean total fecundity ranged from 36 larvae per female at 10°C to 76 larvae at 30°C. On a time scale of days, net reproductive rate (R _o ) increased with increasing temperature while generation time (T) decreased causing the intrinsic rate of increase (r _m ) to increase linearly from 0.115 to 0.465. On a day-degree scaler _m only varied from 0.019 to 0.028 because the growth ofR _o was compensated by an increase inT with increase in temperature. The nearly constantr _m in terms of day-degrees, over a wide range of temperatures, greatly simplifies the prediction of future population numbers ofA. gossypii.     

Alatae production and population increase of aphid vectors on virus-infected host plants

Summary Zucchini yellow mosaic virus (ZYMV) and Aphis gossypii Glover are two components of a recently identified plant-parasite system that provides an excellent opportunity to study interrelations between a virus and a vector that share the same host, but have no direct physiological interaction. In a field experiment we documented numbers of alate and apterous A. gossypii on healthy Cucurbita pepo and on plants inoculated with virus 0, 7, 14, and 21 days before aphid infestation. When plants were inoculated and infested simultaneously, more than twice as many alatae were produced after 20 days of colony growth than on any other treatment. This indicates that properties unique to the early stages of viral infection somehow stimulated wing formation. Because it is spread by the activities of alatae, virus dispersal would be greater as a result of these properties. Developmental rate, total numbers of aphids, and numbers of alatae and apterae decreased as the time between virus inoculation and aphid colonization increased.     

八种杀虫剂对韭菜迟眼蕈蚊发育和繁殖的亚致死效应

用胃毒触杀法确定8种常用杀虫剂对韭菜迟眼蕈蚊Bradysiaodoriphaga 3龄幼虫的LC₂₀和LC₅₀剂量后,以其LC₂₀分别处理3龄幼虫,将存活幼虫正常饲养,测定该剂量药剂对韭菜迟眼蕈蚊化蛹率、蛹重、羽化率,成虫存活率、雌雄比、单雌产卵量及卵孵化率等指标的影响。结果表明:毒死蜱等4种药剂的影响较显著,其影响程度由高到低依次为毒死蜱＞辛硫磷＞阿维菌素溴虫腈;而另4种药剂丙硫克百威、灭多威、丁硫克百威和吡虫啉则影响不显著。此外也测定了用后4种药剂LC₅₀剂量处理的存活试虫的上述生物学指标,结果表明：除化蛹率和羽化率较对照降低且差异显著外,其他生物学指标与对照处理无明显变化。     

伤害和挥发物对棉花花外蜜的诱导效应

植物花外蜜的分泌是一种植物间接防御反应。为了明确植食性昆虫、机械伤和机械伤诱导的挥发性气体在植物花外蜜诱导分泌中的作用,分析了咀嚼式口器昆虫棉铃虫Helicoverpa armigera(Hübner)、刺吸式口器昆虫棉蚜Aphis gossypii Glover取食、剪刀机械伤、剪刀机械伤+棉铃虫反吐物、针刺机械伤以及机械伤诱导挥发物、顺式-茉莉酮对棉花Gossypium hirsutum L.叶片花外蜜分泌量的影响。结果表明,棉铃虫取食、剪刀机械伤、剪刀机械伤+棉铃虫反吐物处理均显著增加了被处理叶片花外蜜的分泌量。棉花花外蜜的诱导效应在处理叶片上表现明显,并且在较幼嫩的第3片真叶上也有系统性增长。顺式-茉莉酮和机械伤挥发物处理1 d对棉花较幼嫩的第4、5片真叶花外蜜有诱导效应。棉花叶片花外蜜的诱导主要与植物组织损伤有关;不同口器类型的昆虫对棉花叶片花外蜜的诱导量不同,咀嚼式口器的棉铃虫对棉花花外蜜的诱导强度显著高于刺吸式口器的棉蚜;顺式-茉莉酮和机械伤诱导的挥发物能作为棉花植株间交流的信息物质诱导棉花幼嫩叶片花外蜜的分泌。     

三种杀虫剂亚致死浓度对川硬皮肿腿蜂繁殖和搜寻行为的影响

在实验室条件下通过药膜法研究了3种杀虫剂对川硬皮肿腿蜂Sclerodermus sichuanensis Xiao成蜂的毒力和对繁殖的亚致死效应,并采用EthoVision3.1行为仪分析了杀虫剂对其搜寻行为的影响.结果表明,川硬皮肿腿蜂对啶虫脒最敏感,致死中浓度LC50和亚致死浓度LC10分别为7.71和4.46 mg/L,其次为吡虫啉(11.22和6.68 mg/L)和功夫菊酯(27.72和9.36 mg/L).经啶虫脒、吡虫啉和功夫菊酯亚致死浓度(LC10)处理的肿腿蜂,亲代、F1和F2代的寄生成功率均受到抑制;经功夫菊酯处理的肿腿蜂,亲代单蜂产卵量显著增加(P＜0.05);经啶虫脒和吡虫啉肿腿蜂,亲代的出蜂率没有显著影响(P＞0.05),但对F1代影响显著(P＜0.05).经啶虫脒和吡虫啉亚致死浓度(LC10)处理的肿腿蜂搜寻行为变弱.结果表明,功夫菊酯对川硬皮肿腿蜂较安全;啶虫脒和吡虫啉对川硬皮肿腿蜂的繁殖和搜寻行为影响较大.研究结果对评估3种药剂对川硬皮肿腿蜂的安全性,为指导合理用药,协调化学防治和生物防治提供科学依据.     

Evaluation of winter wheat as a potential relay crop for enhancing biological control of cotton aphids

A 2-year study was conducted to evaluate the role of winter wheat, Triticum aestivum L., as a potential relay crop to conserve arthropod natural enemies and suppress cotton aphids, Aphis gossypii Glover, in seedling cotton. The results suggested that the natural enemies that moved from the adjacent wheat fields to cotton fields with the maturity and harvest of wheat could keep the cotton aphid population at the edges (0--4 m) of cotton fields under the action threshold of 100 aphids/m². Data also suggested that the wheat strip served as a reservoir to conserve arthropod predators and relayed its predators to cotton when wheat matured and senesced.     

Environmental correlates of the intrinsic rate of natural increase in primates

Morphological and life history traits of two clones of the cladoceran Daphnia pulex were measured in the presence and absence of size-selective insect predators, the midge larva Chaoborus flavicans, which preys on small Daphnia, and the water bug Notonecta glauca, which preys on large Daphnia. The aim was to detect predator-induced phenotypic changes, particularly the effect of simultaneous exposure to both types of predators. Other work has shown that in the presence of Chaoborus americanus, Daphnia pulex produce a socalled neck spine which may carry several teeth. The morphological modifications are supposed to serve as an anti-predator device. Furthermore, females exposed to Chaoborus often delay their maturation; this has been interpreted as a cost that balances the benefits of the neck teeth. In this investigation, females of both clones produced fewer but larger offspring than control animals when reared in the presence of Chaoborus flavicans. The offspring showed the typical neck spine and delayed first reproduction. In the presence of Notonecta glauca, one of the clones produced more and smaller offspring, and maturation occurred at earlier instars. The other clone also produced more offspring than the control but there was no size difference. When both predators were present, in most cases the reactions of the daphnids were similar to those in the Notonecta experiment. The response to Chaoborus appeared to be suppressed. The observed modifications are interpreted as evolved strategies that reduce the impact of size-selective predation. They are consistent with predictions of life-history theory.     

Sublethal effects of selected insecticides on fecundity and wing dimorphism of green peach aphid (Hom., Aphididae)

Effects of sublethal concentrations (LC₂₅) of six insecticides (imidacloprid, rotenone, fenvalerate, abamectin, pirimicarb and azadirachtin) on fecundity and wing dimorphism of the green peach aphid, Myzus persicae (Sulzer), were studied both under laboratory and greenhouse conditions. In the laboratory, aphid reproduction reduced by 44.29% and 54.01% when rotenone and abamectin treatments were applied at sublethal dose, respectively, and sublethal fenvalerate application resulted in markedly lower average reproduction per female per day compared with control. Reproductive duration of aphid treated with abamectin significantly decreased by 44.19%. But in the greenhouse, there were no evident differences in the aphid fecundity and reproductive duration between treatments and control. Life‐table parameters also demonstrated that the six insecticides at sublethal doses did not stimulate the aphid reproductive potential. In the laboratory, after being exposed to sublethal doses of imidacloprid and fenvalerate, the proportions of alate progeny in aphid progeny were significantly higher than that of the control. In the greenhouse, percentages of alate offspring from the mother aphids treated with imidacloprid, fenvalerate and abamectin increased pronouncedly compared with control. Mortality rates of offspring in the nymphal stages from adults treated with insecticides revealed no significant changes between laboratory and greenhouse. The developmental time in days of the offspring varied in all treatments. Mechanisms of insecticide‐induced resurgence are discussed.     

四种杀虫剂亚致死剂量对中黑盲蝽发育和繁殖的影响

使用瓶膜法确定4种常用杀虫剂（毒死蜱、硫丹、氯氟氰菊酯和吡虫啉）对中黑盲蝽Adelphocoris suturalis Jakovlev 1日龄成虫的亚致死剂量（LC₁₀,LC₂₀和LC₃₀）,并研究了其对中黑盲蝽的亚致死效应。结果表明：4种杀虫剂L₂₀剂量处理成虫均能降低雌雄虫的寿命,延长下一代卵的发育历期,但对卵的孵化率没有显著的影响;毒死蜱和硫丹能缩短产卵前期,氯氟氰菊酯和吡虫啉能降低产卵量。毒死蜱亚致死剂量LC₁₀和LC₃₀处理过的成虫与未处理过的成虫交叉配对后雌雄虫寿命均显著缩短;LC10各交叉处理能够缩短产卵历期,降低单雌产卵量和卵的孵化率,延长卵的发育历期;LC₃₀♀×CK♂和LC₃₀♀×LC₃₀♂的下代若虫存活率为28.00％和36.36％,显著低于对照71.88%。结果说明这4种杀虫剂的亚致死剂量对中黑盲蝽生殖均有不利影响,接触杀虫剂与未接触杀虫剂的成虫交配对其后代也有不利影响。研究对于中黑盲蝽区域性综合防治具有一定的指导意义。     

Transgenic Bacillus thuringiensis (Bt) cotton (Gossypium hirsutum) allomone response to cotton aphid, Aphis gossypii, in a closed-dynamics CO(2) chamber (CDCC)

Allocation of allomones of transgenic Bacillus thuringiensis Gossypium hirsutum (Bt cotton) (cv. GK-12) and non-Bt-transgenic cotton (cv. Simian-3) grown in elevated CO₂ in response to infestation by cotton aphid, Aphis gossypii Glover, was studied in a closed-dynamics CO₂ chamber. Significant increases in foliar condensed tannin and carbon/nitrogen ratio for GK-12 and Simian-3 were observed in elevated CO₂ relative to ambient CO_2, as partially supported by the carbon nutrient balance hypothesis, owing to limiting nitrogen and excess carbon in cotton plants in response to elevated CO₂. The CO₂ level significantly influenced the foliar nutrients and allomones in the cotton plants. Aphid infestation significantly affected foliar nitrogen and allomone compounds in the cotton plants. Allomone allocation patterns in transgenic Bt cotton infested by A. gossypii may have broader implications across a range of plant and herbivorous insects as CO₂ continues to rise. Gang Wu and Fa Jun Chen contributed equally to this work.     

Sublethal effects of Beauveria bassiana (Balsamo) Vuillemin (Deuteromycotina: Hyphomycetes) on the whitefly Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) under laboratory conditions

Sublethal effects were evaluated in subsequent generations of whiteflies Bemisia tabaci (Gennadius) arising from parental generations exposed in the four nymphal stages to the fungus Beauveria bassiana (Balsamo) Vuillemin. Examples of such effects include impaired fertility, production of malformations or external variations, and reduced survival of later generations. Malformations of the head, legs, wings or abdomen were not observed in adults derived from treated nymphs, nor were negative effects observed in the fecundity and fertility of the descendants of the whiteflies treated with the fungus. However, moulting problems were observed in insects descended from B. bassiana-treated whiteflies. This is the first time that such effects have been reported, with almost 30% of imagos resulting from treated nymphs unable to detach completely from the exuvia. A gradual reduction in mortality rates between subsequent generations was observed. The importance of these results is discussed in the light of findings from other studies into the effects of entomopathogenic fungi on pest insects.     

11种不同类型杀虫剂对卷蛾分索赤眼蜂繁殖的亚致死效应

在实验室条件下通过药膜法研究了11种不同类型的杀虫剂对卷蛾分索赤眼蜂Trichogrammatoidea bactrae Nagaraja成蜂的毒性, 并研究了杀虫剂对其繁殖的亚致死效应, 旨在评估各药剂对卷蛾分索赤眼蜂成蜂的安全性, 为小菜蛾Plutella xylostella防治过程中杀虫剂的合理施用提供科学依据。研究结果表明, 卷蛾分索赤眼蜂成蜂对阿维菌素最敏感, 致死中浓度LC₅₀和亚致死浓度LC₃₀分别为0.1984和0.1660 mg/L, 其次为氟虫腈（0.2027和0.1903 mg/L）、溴虫腈（0.3069和0.2038 mg/L）、多杀霉素（1.3630和1.0481 mg/L）、杀螟丹（8.1042 和6.7891 mg/L）、高效氯氰菊酯（10.3647和5.8035 mg/L）和丁醚脲（11.5318 和9.9212 mg/L）。经亚致死浓度LC₃₀的阿维菌素、溴虫腈、杀螟丹、丁醚脲、多杀霉素和氟虫腈处理后, 卷蛾分索赤眼蜂的寿命（1.00~1.67 d）显著缩短, 寄生卵量（0~21.70粒/雌）明显降低, 种群参数（净生殖力R₀、内禀增长率r_m、周限增长率λ和世代平均历期T）明显低于对照（P<0.05）。田间推荐浓度的茚虫威、氟啶脲、苏云金杆菌Bacillus thuringiensis、虫酰肼对卷蛾分索赤眼蜂寿命及产卵量均没有不利影响, 但能通过缩短其世代平均历期T, 从而使净生殖力R₀、内禀增长率r_m和周限增长率λ增加。而经亚致死浓度LC₃₀的高效氯氰菊酯处理后, 卷蛾分索赤眼蜂的寿命（3.77 d）显著延长, 寄生卵量（55.47粒/雌）明显提高, 种群参数明显高于对照(P<0.05)。结果说明, 氟啶脲、茚虫威、苏云金杆菌和虫酰肼对卷蛾分索赤眼蜂较安全; 丁醚脲对卷蛾分索赤眼蜂成蜂的寄生能力影响极大, 在田间施用时应当尽量避开卷蛾分索赤眼蜂成蜂的盛发期。     

Influence of <Emphasis Type="Italic">Lecanicillium attenuatum</Emphasis> on the development and reproduction of the cotton aphid, <Emphasis Type="Italic">Aphis gossypii</Emphasis>

The activity of entomopathogens on insect pests has been investigated for many species but the influence of entomopathogenic fungi on factors other than mortality relating to population increase has not been frequently studied. The influence of Lecanicillium attenuatum CS625 (=Verticillium lecanii CS625) on development and reproduction of cotton aphid (Aphis gossypii) was investigated. A conidia suspension of the isolate was applied onto first instar nymphs. Increased spore concentration did not significantly affect each nymphal stage, total nymphal period, pre-reproductive period and the age of first larviposition. A significant dose effect on reduction of life span, reproductive period and fecundity was observed in 1st and 3rd instars after spore application. When conidia were applied to 1st instars, life span was significantly reduced to 10.8 and 8.4 days at 1 × 10⁴ and 1 × 10⁸ conidia/ml, respectively from 12.2 days in the control. During the life span, total fecundity was 41 ± 7.3, 26 ± 0.8 and 22 ± 5.7 nymphs per female at 1 × 10⁴, 1 × 10⁶ and 1 × 10⁸ conidia/ml, respectively compared with 51 ± 2.0 nymphs per untreated female. Reproduction period was also significantly shortened with increasing spore concentration. Application of spores to 3rd instars showed a similar trend. However, daily fecundity of individual aphids was not affected by spore dose. It was concluded that the isolate of L. attenuatum is able to affect populations of cotton aphid by reducing life span and total fecundity as well as by killing the aphids directly.     

Evaluation of Lecanicillium longisporum, Vertalec for simultaneous suppression of cotton aphid, Aphis gossypii, and cucumber powdery mildew, Sphaerotheca fuliginea, on potted cucumbers

The commercial preparation of Lecanicillium longisporum, Vertalec^® was evaluated for simultaneous suppression of cotton aphid and cucumber powdery mildew on potted cucumber plants. Vertalec was applied onto cucumber plants that had been infested with either cotton aphid, spores of Sphaerotheca fuliginea or both. Irradiation-inactivated Vertalec (II Vertalec) was also applied to an identical series of cucumber plants as a control. The Vertalec was highly pathogenic against adult aphids with an LT₅₀ of 6.9 days. II Vertalec did not affect aphid survival. Application of either active or II Vertalec significantly suppressed spore production of S. fuliginea compared to the water control. For dual control assays, Vertalec applications were made one day after infestation of both aphid and S. fuliginea onto potted cucumbers. Fifteen days after the Vertalec treatments, the numbers of surviving aphids and the production of powdery mildew spores were significantly reduced compared with the water control. The presence of aphids also suppressed S. fuliginea spore production. Our results suggest the potential of a dual role for Vertalec as a microbial control agent of aphids and powdery mildew in cucumber.     

取食不同寄主植物对棉蚜后代抗药性的影响

测定了5种药剂对棉蚜Aphis gossypii抗氰戊菊酯、吡虫啉品系和敏感品系取食棉花、黄瓜和石榴的后代的毒力,并对它们的后代体内乙酰胆碱酯酶和羧酸酯酶的比活力做了初步探索。结果表明,氰戊菊酯抗性品系取食棉花比取食黄瓜的后代对氰戊菊酯的抗性大76.4倍,对灭多威、氧乐果、硫丹和吡虫啉的抗性也大0.5～4.6倍;取食石榴的后代对5种药剂的抗性介于取食棉花和黄瓜的之间。吡虫啉抗性品系的测定结果与氰戊菊酯抗性品系基本一致。敏感品系取食黄瓜比取食棉花的后代对5种药剂的敏感性更高。3个品系取食不同植物的后代相比,其体内乙酰胆碱酯酶的比活力,取食棉花的为取食黄瓜的2.4～2.8倍;羧酸酯酶的比活力,取食棉花的为取食黄瓜的1.8～2.4倍。证明棉蚜的抗性和敏感品系取食的寄主植物不同,可引起对药剂敏感性的变化。乙酰胆碱酯酶和羧酸酯酶活力的变化均是引起这种变化的重要因素。     

Sublethal effects on seabirds after the Prestige oil-spill are mirrored in sexual signals

It has been suggested that sexual signals may be a useful measure of environmental quality as they represent the sum of environmental pressures on the animal. Accordingly, it has been proposed that carotenoid-based coloration may be especially valuable in monitoring and detecting the sublethal effects of toxic pollutants in the environment. Here, we evaluate whether the carotenoid-based coloration in the bill of adult yellow-legged gulls reflects oil-induced sublethal effects in breeding colonies affected by the Prestige oil spill. In 2004, we took blood samples from 27 adult birds at four insular breeding colonies located in the pathway of the Prestige oil spill. We measured the size of the red bill spot area and analysed plasma biochemical parameters indicative of sublethal effects of oil contamination in gulls, including glucose, total protein, creatinine, inorganic phosphorus, aspartate aminotransferase (AST) and gamma-glutamyl transferase. We showed that the size of their red bill spot area was positively related to body condition, while negatively related with AST levels, an enzyme that is commonly used as an indication of hepatic damage in birds. Hence, the present study provides support for the idea that carotenoid-based colour integuments may be a useful measure of environmental quality.     

氰氟虫腙亚致死剂量对甜菜夜蛾生长发育和繁殖力的影响

本文研究了氰氟虫腙的亚致死剂量LC15(28.423μg/mL)和LC25(41.363μg/mL)对甜菜夜蛾Spodoptera exigua(Hübner)亲代和子1代的一些生物学特性的影响。结果表明:LC15和LC25处理组与对照组相比,甜菜夜蛾亲代的化蛹率,羽化率和单雌产卵量分别降低了49.3%,60.0%;♀(12.65%,25.09%)和♂(13.14%,28.91%);25.6%,65.7%,畸形蛹率分别提高了10.5%,14.4%。子1代的化蛹率,羽化率和单雌产卵量分别降低了11.8%,24.6%;♀(9.48%,21.54%)和♂(11.61%,24.08%);14.4%,54.3%,畸形蛹率分别提高了4.1%,5.8%。另外子1代的孵化率、幼虫的存活率降低,蛹期和成虫期缩短,产卵前期延长,产卵期显著缩短。总体来说,LC15和LC25剂量的氰氟虫腙对甜菜夜蛾亲代与子1代的生物特性都有不同程度的影响,并且LC25剂量对甜菜夜蛾的影响要比LC15剂量大。     

Fecundity,reproductive rate,longevity, and intrinsic rate of increase of an aphidiid parasitoidLysiphlebia mirzai

A life-table was constructed for a little known aphidiid waspLysiphlebia mirzai, a parasitoid of cereal aphid,Rhopalosiphum maidis. The female parasitoid survived 6.4 ± 1.17 (SD) days and oviposited intensively 4.0 ± 0.47 days. The total fecundity rate, R_t, was 169.2 ± 6.94 mummies/female and net reproductive rate, R_o, was 92.70 female offspring/female. The intrinsic total fecundity rate, r_t, and intrinsic rate of natural increase, r_m, the finite rate of total fecundity, λ^t, and finite rate of increase, λ^m, was 0.27048, 0.24155, 1.31059 and 1.27322 respectively. The mean generation time (18.75 days) and doubling time of the population (2.87 days) was slightly higher than other aphidiids studied so far. The proportion of female progenies decreased significantly on the successive oviposition days.