Insect Natural Enemies Research Articles

Cool Headed Individuals Are Better Survivors: Non-Consumptive and Consumptive Effects of a Generalist Predator on a Sap Feeding Insect.

Non-consumptive effects (NCEs) of predators are part of the complex interactions among insect natural enemies and prey. NCEs have been shown to significantly affect prey foraging and feeding. Leafhopper's (Auchenorrhyncha) lengthy phloem feeding bouts may play a role in pathogen transmission in vector species and also exposes them to predation risk. However, NCEs on leafhoppers have been scarcely studied, and we lack basic information about how anti-predator behaviour influences foraging and feeding in these species. Here we report a study on non-consumptive and consumptive predator-prey interactions in a naturally co-occurring spider–leafhopper system. In mesocosm arenas we studied movement patterns during foraging and feeding of the leafhopper Psammotettix alienus in the presence of the spider predator Tibellus oblongus. Leafhoppers delayed feeding and fed much less often when the spider was present. Foraging movement pattern changed under predation risk: movements became more frequent and brief. There was considerable individual variation in foraging movement activity. Those individuals that increased movement activity in the presence of predators exposed themselves to higher predation risk. However, surviving individuals exhibited a ‘cool headed’ reaction to spider presence by moving less than leafhoppers in control trials. No leafhoppers were preyed upon while feeding. We consider delayed feeding as a “paradoxical” antipredator tactic, since it is not necessarily an optimal strategy against a sit-and-wait generalist predator.

Landscape composition affects parasitoid spillover

The intensification of agriculture has led to a severe simplification of agricultural landscapes, resulting in a marked reduction in the diversity of insect natural enemies. However, how this simplification shapes the movement of insect parasitoids between crop and non-crop habitats (i.e., spillover) is still unclear. We examined the potential spillover of tachinid parasitoids from semi-natural habitats into apple orchards across different landscapes. We sampled commercial apple orchards localized in three landscape types (forest-, grassland- or apple-dominated landscapes) to first evaluate if landscape composition affects the local species richness in apple orchards. Second, we tested whether the contribution of forest and grassland habitats to the local tachinid community composition of apple orchards changes according to landscape composition. We found that landscape composition did not affect local tachinid species richness in apple orchards, while it affected the species spillover. Independently of the landscape, we found highly nested communities of tachinids between apple orchards and forest habitats suggesting a strong spillover of tachinids between these habitats. In contrast, tachinids in apple orchards were nested with grassland habitats only in landscapes dominated by apple orchards. Our results have important implications for the conservation of insect parasitoids in agricultural landscapes, as the spillover of species in the crop can be affected by the type and the area of semi-natural habitats in the surrounding landscape.

Effect of Parasitoid: Host Ratio and Group Size on Fitness of Spathius galinae (Hymenoptera: Braconidae): Implications for Mass-Rearing.

Producing insect natural enemies in laboratories or insectaries for biological pest control is often expensive, and developing cost-effective rearing techniques is a goal of many biological control programs. Spathius galinae Belokobylskij and Strazenac (Hymenoptera: Braconidae), a newly described ectoparasitoid of emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), is currently being evaluated for environmental introduction in the United States to provide biological control of this invasive pest. To improve mass-rearing outcomes for S. galinae, we investigated the effects of parasitoid: host ratio and parasitoid and host group size (density) on parasitoid fitness. Our results showed that when 1 emerald ash borer larva was exposed to 1, 2, 4, or 8 female parasitoids, parasitism rate was positively associated with increasing parasitoid: host ratio, while brood size, sex ratio, and fitness estimates of progeny were not affected. When a constant 1:1 parasitoid: host ratio was used, but group size varied from 1 female parasitoid and 1 host, 5 parasitoids and 5 hosts, 10 of each, and 20 of each in same size rearing cages, parasitism rates were highest when at least 5 females were exposed to 5 host larvae. Moreover, the number of progeny produced per female parasitoid was greatest when group size was 10 parasitoids and 10 hosts. These findings demonstrate that S. galinae may be reared most efficiently in moderately high-density groups (10 parasitoids and hosts) and with a 1:1 parasitoid: host ratio.

Parasitism and Suitability of Different Egg Ages of the Leguminivora glycinivorella (Lepidoptera: Tortricidae) for Three Indigenous Trichogramma Species

Pod borers are economically important soybean pests in temperate and tropical regions. However, the biological control of these pests using their natural insect enemies has been poorly studied to date. Indigenous natural populations of three Trichogramma (Hymenoptera: Trichogrammatidae) species, Trichogramma chilonis Ishii, Trichogramma ostriniae Pang & Chen, and Trichogramma leucaniae Pang & Chen, were collected from Leguminivora glycinivorella (Matsumura) (Lepidoptera: Tortricidae) eggs in soybean fields in China. In this study, we compare the parasitic capacities and suitabilities of three indigenous Trichogramma species on L. glycinivorella eggs at various ages. Host eggs of all ages were accepted by T. chilonis, T. ostriniae, and T. leucaniae. T. chilonis tended to parasitize 0-2-d-old eggs more than 3-4-d-old eggs. There were no significant differences in parasitism between the 0-2-d-old eggs and the 1-4-d-old eggs for T. ostriniae and T. leucaniae. For eggs at various ages, T. chilonis parasitized the smallest number of eggs, while T. leucaniae and T. ostriniae exhibited similar parasitic capacities. With 0-d-old host eggs, T. ostriniae developed over the longest time period (8.7 d), and T. leucaniae produced the most female progeny (87.9%). Both T. leucaniae and T. ostriniae had similar developmental times, survival rates and percentages of female progeny with 1-3-d-old eggs. These results show that T. leucaniae can parasitize host eggs at varying ages with the best development and suggest that it may be a valuable biological control agent for soybean pod borers.

Molecular identification of sibling species of Sclerodermus (Hymenoptera: Bethylidae) that parasitize buprestid and cerambycid beetles by using partial sequences of mitochondrial DNA cytochrome oxidase subunit 1 and 28S ribosomal RNA gene.

The species belonging to Sclerodermus (Hymenoptera: Bethylidae) are currently the most important insect natural enemies of wood borer pests, mainly buprestid and cerambycid beetles, in China. However, some sibling species of this genus are very difficult to distinguish because of their similar morphological features. To address this issue, we conducted phylogenetic and genetic analyses of cytochrome oxidase subunit I (COI) and 28S RNA gene sequences from eight species of Sclerodermus reared from different wood borer pests. The eight sibling species were as follows: S. guani Xiao et Wu, S. sichuanensis Xiao, S. pupariae Yang et Yao, and Sclerodermus spp. (Nos. 1–5). A 594-bp fragment of COI and 750-bp fragment of 28S were subsequently sequenced. For COI, the G-C content was found to be low in all the species, averaging to about 30.0%. Sequence divergences (Kimura-2-parameter distances) between congeneric species averaged to 4.5%, and intraspecific divergences averaged to about 0.09%. Further, the maximum sequence divergences between congeneric species and Sclerodermus sp. (No. 5) averaged to about 16.5%. All 136 samples analyzed were included in six reciprocally monophyletic clades in the COI neighbor-joining (NJ) tree. The NJ tree inferred from the 28S rRNA sequence yielded almost identical results, but the samples from S. guani, S. sichuanensis, S. pupariae, and Sclerodermus spp. (Nos. 1–4) clustered together and only Sclerodermus sp. (No. 5) clustered separately. Our findings indicate that the standard barcode region of COI can be efficiently used to distinguish morphologically similar Sclerodermus species. Further, we speculate that Sclerodermus sp. (No. 5) might be a new species of Sclerodermus.

Does the Aphid Alarm Pheromone (E)-β-farnesene Act as a Kairomone under Field Conditions?

Insect natural enemies use several environmental cues for host/prey finding, and adjust their foraging behavior according to these signals. In insects, such cues are mainly chemical, derived from the host plant or the prey itself. The aphid alarm pheromone, (E)-β-farnesene (EBF), is believed to be such a cue, because several aphid enemies are able to perceive EBF and show attractant behavior. These studies are, however, based mainly on electroantennogram or olfactometer assays, and often use unnaturally high pheromone concentrations. It is, therefore, unclear if EBF is used to locate prey in the field when only naturally released amounts are present. We monitored the frequencies and durations of plant visits by aphid natural enemies in the field using long-duration camera observations. By placing pheromone releasers emitting no, natural or exaggerated amounts of EBF next to small colonies of pea aphids (Acyrthosiphon pisum), we analyzed if EBF presence altered long-range foraging behavior of natural enemies. Thirteen potential groups of aphid natural enemies were observed in 720 hr of analyzed video data. There was no effect of EBF on the number of predator visits to an aphid colony, or on predator patch residence times. The number of plant visits increased at exaggerated EBF amounts but not at natural EBF levels. We conclude that while there may be potential for use of high EBF concentrations for agricultural pest management strategies, an ecological role of EBF as a kairomone in a natural context is doubtful.

Structure-Based Analysis of the Ligand-Binding Mechanism for DhelOBP21, a C-minus Odorant Binding Protein, from Dastarcus helophoroides (Fairmaire; Coleoptera: Bothrideridae).

Odorant binding proteins (OBPs) transport hydrophobic odor molecules across the sensillar lymph to trigger a neuronal response. Herein, the Minus-C OBP (DhelOBP21) was characterized from Dastarcus helophoroides, the most important natural parasitic enemy insect that targets Monochamus alternatus. Homology modeling and molecular docking were conducted on the interaction between DhelOBP21 and 17 volatile molecules (including volatiles from pine bark, the larva of M. alternatus, and the faeces of the larva). The predicted three-dimensional structure showed only two disulfide bridges and a hydrophobic binding cavity with a short C-terminus. Ligand-binding experiments using N-phenylnaphthylamine (1-NPN) as a fluorescent probe showed that DhelOBP21 exhibited better binding affinities against those ligands with a molecular volume between 100 and 125 ų compared with ligands with a molecular volume between 160 and 185 ų. Molecules that are too big or too small are not conducive for binding. We mutated the amino acid residues of the binding cavity to increase either hydrophobicity or hydrophilia. Ligand-binding experiments and cyber molecular docking assays indicated that hydrophobic interactions are more significant than hydrogen-bonding interactions. Although hydrogen-bond interactions could be predicted for some binding complexes, the hydrophobic interactions had more influence on binding following hydrophobic changes that affected the cavity. The orientation of ligands affects binding by influencing hydrophobic interactions. The binding process is controlled by multiple factors. This study provides a basis to explore the ligand-binding mechanisms of Minus-C OBP.

Aboveground Arthropod Composition, Abundance and Guild Structure in Upland Rice Agro-ecosystem at Matalam, North Cotabato, Philippines

With the recent innovations in the field of ecological pest management,conservation and enhancement of biological diversity at any rice agro-ecosystemshas received considerable attention. The composition and abundance ofaboveground arthropods was assessed on upland rice fields in Matalam, NorthCotabato, Southern Mindanao, Philippines. Sampling and monitoring was doneusing malaise trapping, sweep netting and direct counting techniques. A total of29 arthropod species belonging to 21 families in nine orders were documented.The collected samples were comprised of 40% insect pests, 53% predators and7% parasitoids. The three most abundant insect pests were rice bug (Leptocorisaoratorius), rice seedling maggot (Atherigona oryzae), and pink stemborer (Sesamia inferens). The predators are dominated by lady bird beetle (Micraspis spp.), social wasp (unknown) and long-jawed spider (Tetragnatha maxillosa). Ichneumonids,Braconids and Tachinids, though in smaller numbers, were present throughoutthe cropping season. More importantly, the study reported the presence of four rice stem borer species – Scirpophaga innotta, Scirpophaga incertulas, Sesamia infere and Chilo suppressalis and two rice grain bug species – Paraeucosmetuspallicornis and Elasmolomus sordidus in Matalam. The occurrence, compositionand abundance of insect pests and associated natural enemies vary with ricegrowth and developmental stages. The negative Pearson’s correlation coefficient (r= -0.31) between the insect pests and natural enemies was attributed to effectivecultural management practices which have been developed through decades ofsubsistence upland rice farming.Keywords: Ecology, aboveground arthropods, upland rice agro-ecosystem, sampling andmonitoring, Philippines

The role of natural enemy foraging guilds in controlling cereal aphids in Michigan wheat.

Insect natural enemies (predators and parasitoids) provide important ecosystem services by suppressing populations of insect pests in many agricultural crops. However, the role of natural enemies against cereal aphids in Michigan winter wheat (Triticum aestivum L.) is largely unknown. The objectives of this research were to characterize the natural enemy community in wheat fields and evaluate the role of different natural enemy foraging guilds (foliar-foraging versus ground-dwelling predators) in regulating cereal aphid population growth. We investigated these objectives during the spring and summer of 2012 and 2013 in four winter wheat fields on the Michigan State University campus farm in East Lansing, Michigan. We monitored and measured the impact of natural enemies by experimentally excluding or allowing their access to wheat plants infested with Rhopalosiphum padi (L.) and Sitobion avenae (F.) (Hemiptera: Aphidae). Our results indicate that the natural enemy community in the wheat fields consisted mostly of foliar-foraging and ground-dwelling predators with relatively few parasitoids. In combination, these natural enemy groups were very effective at reducing cereal aphid populations. We also investigated the role of each natural enemy foraging guild (foliar-foraging versus ground-dwelling predators) independently. Overall, our results suggest that, in combination, natural enemies can almost completely halt early-season aphid population increase. Independently, ground-dwelling predators were more effective at suppressing cereal aphid populations than foliar-foraging predators under the conditions we studied. Our results differ from studies in Europe and the US Great Plains where foliar foraging predators and parasitoids are frequently more important cereal aphid natural enemies.

Effect of abiotic factors on population dynamics of insect pests and natural enemies in potato crop

Insect population dynamics studies in potato crop revealed the occurrence of insect pests of different groups among which the major pests viz. Lepidopterans (Helicoverpa spp., Spodoptera spp., and Agrotis spp.) attained population peaks during initial stages of the crop (June- July), whereas scarabids (Brahmina spp., Holotrichia spp.,) were confined to active growing stage of the crop (JulyAugust) which coincided with monsoon showers. A positive correlation was observed between the insect pest trap catch and abiotic factors viz. maximum temperature (‘r’=0.63 and 0.50) and minimum temperature (‘r’=0.60 and 0.52), relative humidity (‘r’=0.62 and 0.20) and rainfall (‘r’=0.22 and 0.19) during the year 2011 and 2012, respectively. The corresponding periodical sampling for natural enemies revealed the occurrence of coccinellids, syrphids, Chrysoperla carnea and parasitoids like Aphelinus abdominalis and Aphidius sp. The association between predators and or parasitoids with the abiotic factors revealed a positive correlation with their population fluctuation but in case of parasitoids, a negative but non-significant correlation was observed with minimum temperature (‘r’= -0.15) and relative humidity during 2011 (‘r’=-0.23) and with rainfall during 2011 (‘r’=0.20) and 2012 (‘r’=0.15) respectively.

Grassland plantings and landscape natural areas both influence insect natural enemies

Local habitat management and landscape composition are main factors in determining the abundance and diversity of conservation biological control agents. In Midwestern U.S.A., the establishment of conservation plantings is encouraged through government programs. These plantings buffer streams from agricultural inputs and increase wildlife habitat. We examined the effects that these plantings and semi-natural areas in the surrounding landscape have upon the abundance and diversity of natural enemies of the soybean aphid. We quantified abundances of soybean aphids and their natural enemies in soybean fields and adjacent plantings in Newton County, Indiana, U.S.A. We found a higher number of natural enemies in conservation plantings than in soybean fields before aphids arrived. When soybean aphid populations were increasing, aphid abundance was a main factor influencing the four major predator groups (Anthocoridae, Nabidae, and exotic and native Coccinellidae). Along with aphid abundance, the presence of adjacent plantings and forest areas within 3km affected nabid abundance and the presence of adjacent plantings and grassy areas within 5km influenced the abundance of native coccinellid in soybean fields. Lastly, this study showed that the presence of grassland strips enhances beta diversity of natural enemies in soybean fields. Therefore, natural enemy communities may be more resilient to disturbance in landscapes containing conservation plantings. The increased natural enemy abundance with plantings and semi-natural areas in the surrounding landscape may enhance conservation biological control and benefit farmers.

Sex ratio effects on copulation, fecundity and progeny fitness for Agasicles hygrophila, a biological control agent of alligator weed

Determining the best ratio of females to males of an insect's natural enemy is important for maximising population increase and promoting population establishment of a natural enemy. In this study, copulation behaviour, fecundity, progeny fitness and rate of population increase for the flea beetle, Agasicles hygrophila Selman & Vogt (Coleoptera: Chrysomelidae), were compared at different female percentage treatments (i.e., 80%, 66.7%, 50%, 33.3% and 20% females). The results showed that the copulation frequency and duration in males decreased, whereas those in females increased as the number of males increased. At 20%, 33.3% and 66.7% females, the rates of population increase were 3.4-, 2.17- and 0.79-fold higher than that at 50% females. Females at 20% and 33.3% were found to be optimal for mass rearing of the beetle.

Transcriptome analysis of Dastarcus helophoroides (Coleoptera: Bothrideridae) using Illumina HiSeq sequencing.

Background Dastarcus helophoroides is known as the most valuable natural enemy insect against many large-body longhorned beetles. The molecular mechanism of its long lifespan and reproduction makes it a unique resource for genomic research. However, molecular biological studies on this parasitic beetle are scarce, and genomic information for D. helophoroides is not currently available. Thus, transcriptome information for this species is an important resource that is required for a better understanding of the molecular mechanisms of D. helophoroides. In this study, we obtained transcriptome information of D. helophoroides using high-throughput RNA sequencing.ResultsUsing Illumina HiSeq 2000 sequencing, 27,543,746 clean reads corresponding to a total of 2.48 Gb nucleotides were obtained from a single run. These reads were assembled into 42,810 unigenes with a mean length of 683 bp. Using a sequence similarity search against the five public databases (NR, Swiss-Prot, GO, COG, KEGG) with a cut-off E-value of 10−5 using Blastx, a total of 31,293 unigenes were annotated with gene description, gene ontology terms, or metabolic pathways.ConclusionsTo the best of our knowledge, this is the first study on the transcriptome information of D. helophoroides. The transcriptome data presented in this study provide comprehensive information for future studies in D. helophoroides, particularly for functional genomic studies in this parasitic beetle.

東アフリカ，ウガンダのイネにおける害虫と天敵の発生

東アフリカ，ウガンダのイネにおける害虫と天敵の発生

肿腿蜂类寄生蜂室内控害效能评价：以松脊吉丁肿腿蜂为例

PDF HTML阅读 XML下载 导出引用 引用提醒 肿腿蜂类寄生蜂室内控害效能评价——以松脊吉丁肿腿蜂为例 DOI: 10.5846/stxb201308062037 作者: 作者单位: 中国林业科学研究院森林生态环境与保护研究所,中国林业科学研究院森林生态环境与保护研究所,中国林业科学研究院森林生态环境与保护研究所,中国林业科学研究院森林生态环境与保护研究所,中国林业科学研究院森林生态环境与保护研究所,中国林科院森林生态环境与保护研究所,中国林科院森林生态环境与保护研究所,新疆林科院,中国林科院森林生态环境与保护研究所,中国林科院森林生态环境与保护研究所 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然基金重点项目（31230015）；“863”计划项目（2012AA100703） Evaluation on control efficiency of bethylid parasitoids on pest insects indoor：a case of Sclerodermus sp. (Hymenoptera：Bethylidae) Author: Affiliation: Chinese Academy of Forestry,Chinese Academy of Forestry,,,,,,,, Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:为了开发利用天敌资源防治害虫，科学而客观地评价肿腿蜂对蛀干害虫的控害作用，研究了松脊吉丁肿腿蜂（Sclerodermus sp.）对松褐天牛3龄幼虫的功能反应，建立了肿腿蜂类寄生蜂室内控害效能评价体系，并证明了其可行性。该评价体系包括供试虫源标准、寄生蜂生物学与寄生行为学观察、寄生蜂对寄主的功能反应和寻找寄主效应以及寄生蜂的忠岐指数（Y）4个部分。研究结果表明：松脊吉丁肿腿蜂具有较强的控害潜力，单头雌成虫能防治3-4头松褐天牛3龄幼虫，21d内最多可致死9.07头寄主幼虫；寄主密度对单头寄生蜂寄生作用功能反应的测定结果与对寄生作用寻找效应的测定结果以及对产卵量影响的测定结果一致；综合评价该蜂对松褐天牛3龄幼虫控制效能，释放比为1∶1（即1头肿腿蜂雌蜂：1头3龄松褐天牛幼虫）时最高，其忠岐指数Y为39.63，这可能是肿腿蜂类天敌特有的抚幼习性所致，结论也与寄生蜂生物学特性及寄生行为学观察结果相同。研究结论证明该评价体系是稳定可靠的。评价体系在利用天敌昆虫生物防治害虫时为筛选最佳寄生性天敌种类提供了可行的方法和依据。 Abstract:To evaluate the control efficiency of the bethylid parasitoids in suppressing wood-borer pests for biological application of the insect natural enemy group resources, the functional response of Sclerodermus sp., (Hymenoptera: Bethylidae) on 3rd instar larvae of Monochamus alternatus Hope (Coleoptera: Cerambycidae) was studied. A consummate evaluation system of control efficiency was established and its feasibility was clarified. The evaluation system consists of four parts: the standard of experimental insects, study on biological characters of parasitism behavior of the bethylid, the functional response of parasitoid and Zhongqi Index. The results indicated that one bethylid female could control 3-4 3rd instar larvae of M. alternates, the maximum quantity of hosts had been killed was 9.07 in 21days, the Sclerodermus sp. had great potential for control the wood borer pest. The result of parasitism functional response on one parasitoid wasp to different diversities of hosts was consistent to the host-searching efficiency and similar to the impact on the fecundity. Comprehensive evaluation indicated that the control efficiency of the bethylid on 3rd instar larvae of M. alternates was highest at 1:1 (releasing number property of parasitoid and its host), the Zhongqi Index was 39.63, which probably was caused by the bethylid's brood guarding behavior. That has certain similary with the observation on biological characters of parasitic behavior. Above all, the evaluation system is steadily, which could be used for biological control to screen out optimal parasitic wasp species for biological control application. 参考文献 相似文献 引证文献

Epiphytic lichen is associated with species richness of gall-inducing aphids but not with niche differentiation among them

The presence of epiphytic foliose lichen amplifies the heterogeneity of habitat by creating shelters for insects living on tree bark. It thus should enhance species number and spatial niche segregation among these canopy insects. We studied this hypothesis in a field experiment using four aphid species that induce galls on Pistacia atlantica trees covered with Xanthoria parietina lichen. In autumn 2008, 3 months after aphid fundatrices were oviposited, we marked six branches on each of 29 trees. Two served as a control, whereas the other four were isolated with insect glue; two of them were scraped with sandpaper to remove epiphytic foliose lichens. We therefore obtained three treatments comprising control branches, isolated branches with lichen, and isolated branches without lichen. In summer 2009, we counted all the galls developing on five new annual shoots on each of 174 branches. We observed more cecidogenic aphid species on all the branches with lichens than without, but each species at different proportions. The different frequencies of utilization of the lichen did not lead to habitat partitioning between species. In conclusion, although habitat heterogeneity itself was associated with species richness and population abundance, it did not induce spatial niche segregation. Considering that many economically important insect species, pests and natural enemies, oviposit or spend some portion of their lives in bark cracks, it is possible that some can use lichens too for protection or/and oviposition sites. As a consequence, lichens may affect management of agrosystems and their impacts should be investigated more deeply in such contexts.

Effects of host-egg ages on host selection and suitability of four Chinese Trichogramma species, egg parasitoids of the rice striped stem borer, Chilo suppressalis

The striped stem borer, Chilo suppressalis (Walker), is one of the most economically important rice pests worldwide. However, biological control of this pest using natural-enemy insects has been rarely documented to date. With the objective of screening suitable candidate species for controlling the striped stem borer, we investigated the effect of the age of host eggs on the host selection and suitability by four indigenous Trichogramma species on their native host, C. suppressalis. The results indicated that the differently aged eggs of C. suppressalis were all accepted by T. japonicum, T. dendrolimi and T. chilonis, and there was a clear tendency to parasitize older eggs less under no-choice and choice conditions. The number of parasitized host eggs by T. ostriniae also decreased with the increasing host age in the no-choice test, but more 2-day-old host eggs were parasitized in the choice test. When 0-, 2-day-old eggs were offered, T. dendrolimi, T. japonicum and T. chilonis exhibited similar parasitism ability, whereas T. ostriniae appeared to have a stronger ability to attack the older host eggs (4-day-old). Trichogramma japonicum developed and emerged on parasitized C. suppressalis eggs of all ages tested, while showing a better adaptation to younger host eggs with significantly faster developmental time, higher survival and more female progeny on 0-day-old eggs. No adults for each of the other three Trichogramma species emerged from parasitized 4-day-old host eggs, and they had similar developmental time, survival and female progeny on parasitized 0-, 2-day-old host eggs with an exception of female progeny for T. chilonis. On 0-day-old host eggs, T. japonicum developed faster and T. ostriniae had lower progeny survival than the other three Trichogramma species evaluated, respectively. The current study provides useful information to select suitable Trichogramma species for controlling the striped stem borer, C. suppressalis.

Hybrid approach for pest control with impulsive releasing of natural enemies and chemical pesticides: A plant–pest–natural enemy model

The agricultural pests can be controlled effectively by simultaneous use (i.e., hybrid approach) of biological and chemical control methods. Also, many insect natural enemies have two major life stages, immature and mature. According to this biological background, in this paper, we propose a three tropic level plant–pest–natural enemy food chain model with stage structure in natural enemy. Moreover, impulsive releasing of natural enemies and harvesting of pests are also considered. We obtain that the system has two types of periodic solutions: plant–pest-extinction and pest-extinction using stroboscopic maps. The local stability for both periodic solutions is studied using the Floquet theory of the impulsive equation and small amplitude perturbation techniques. The sufficient conditions for the global attractivity of a pest-extinction periodic solution are determined by the comparison technique of impulsive differential equations. We analyze that the global attractivity of a pest-extinction periodic solution and permanence of the system are evidenced by a threshold limit of an impulsive period depending on pulse releasing and harvesting amounts. Finally, numerical simulations are given in support of validation of the theoretical findings.

Effect of Garlic and Eucalyptus oils in comparison to Organophosphatinsecticides against some Piercing-Sucking Faba bean insect Pests and natural enemies populations

The efficacy of garlic Allium sativum oil, and eucalyptus Eucalyptus globulus oil and their combinations with two organophosphorus pesticides, Dimethoate 30 % and Pestban 48% were evaluated for the control of some Piercing-Sucking insect pests associated with Faba bean Vicia faba in open field, during season 2011/2012. All of the four composites diluted to 3% before applying for four times in each spray. Samples were taken at the first, fifth, seventh and tenth days after application to determine the reduction in numbers. The results showed that, garlic oil was the best efficient in reducing the population of leafhoppers and planthoppers by a mean reduction percentage of 68.09%, followed by the two chemical insecticides Dimethoate 67.90 % and Pestban 64.02 %, and Eucalyptus oil was the least in this category as 43.27 %. However in controlling aphids, also garlic surpasses again by a mean overall reduction 90.96 %, followed by Pestban 89.44 %, while eucalyptus oil came in the third rank as 80.66 % before the dimethoate which achieved the least rank in controlling aphids as 76.14 %. Furthermore experiment was conducted also to evaluate the side effects of such composites on the population fluctuations of two insect predators rife in Fababean fields, true spiders and minute pirate bug (Orius sp.). Data showed that, in compared with control, the use of natural oils preserved partly the coexist of natural enemies than the use of chemical compounds in Faba bean fields.

The Effect of using Tertiary Treated Sewage Water in Irrigation on Cadmium (Cd) and Lead (Pb) Content in Alfalfa Crop and Insects Living on it

This study was conducted during the period April 2009 to March 2010 in the Northern Governorate, Kingdom of Bahrain to study the relation between water quality and Nitrogen, Phosphorus, Cadmium and Lead contents of alfalfa crop and insects living on it. The study was conducted on 6 farms, 3 irrigated with underground water and the other 3 irrigated with tertiary treated sewage effluents (TTSE). Plant samples were collected during April in 5 replications, randomly from each farm using a 25×25 cm metal frame for estimation of Nitrogen using (Kjeltec apparatus 2300), and Phosphorus by (Spectrophotometer), Cadmium and Lead content by (Atomic Absorption Spectrophotometer). Pitfall traps and sweeping nets were used to collect insects for analyses for Lead and Cadmium content. Results indicated that water type did not affect alfalfa, Nitrogen and Cadmium contents. Average Nitrogen content was 2.6 and 3% in alfalfa irrigated with groundwater and (TTSE), respectively. And Phosphorus content was 0.33 and 0.4% in alfalfa irrigated with ground water and (TTSE), respectively. Results also showed that irrigation with (TTSE) did not significantly affect Cadmium and Lead contents in alfalfa crop. The average concentrations of these two elements were 0.41 and 0.35 ppm, respectively, their concentrations in alfalfa irrigated with TTSE were 0.44 and 0.34 ppm, respectively. The concentrations of Cadmium and Lead in insects living on ground water irrigated alfalfa were 0.14 and 0.063 ppm, respectively, and in TTSE irrigated alfalfa were 0.338 and 0.076 ppm respectively. Cadmium and Lead concentrations were found to increase in the natural enemies of insects living on alfalfa irrigated with (TTSE) indicating biomagnification of those heavy metals in the food chain from alfalfa to insect pests and predators.