Propylaea Japonica Research Articles

Design the fusion double-strand RNAs to control two global sap-sucking pests

RNA interference (RNAi) is an effective pest management strategy through silencing the crucial genes in target organisms. However, the effectiveness of targeting a single gene is often limited by the silencing efficiency due to tissue or developmental stage-specific gene expression. Moreover, multiple pests often infest the same crop simultaneously under current ecological conditions. Therefore, a combined strategy of “targeting multiple genes” and “controlling multiple pests” is expected to yield better management results. In this study, homologous genes from two globally sap-sucking pests, the peach aphid (Myzus persicae) and the whitefly (Bemisia tabaci), were screened on a genome-wide scale. Subsequently, RNAi bioassays showed silencing the genes (MpAbd-A, MpH3, MpRpL27a, and MpScr) exhibited high mortalities in both species, which were further selected for designing fusion dsRNAs. These fusion dsRNAs resulted in higher mortalities in both pests than single gene silencing and posed a minimal off-target risk to the predator ladybeetle (Propylaea japonica) based on the sequence analysis. Finally, the tobacco plants expressing the fusion dsRNAs through virus-induced gene silencing (VIGS) technology enhanced the resistance to both pests. In conclusion, this study proposes a novel RNAi-based approach for managing two sap-sucking pests simultaneously.

Effects of Crop Resistance on the Tritrophic Interactions between Wheat Lines, Schizaphis graminum (Hemitera: Aphididae), and Propylaea japonica (Coleoptera: Coccinellidae).

Crop resistance and biological control are both considered efficient and environmentally friendly methods of sustainable pest control. In this study, we aimed at investigating the direct influence of four wheat lines with varying resistance level on the life-history traits of the greenbug, Schizaphis graminum, and the mediational effect on the functional response of a predatory ladybird, Propylaea japonica, under laboratory conditions. Results showed that the aphid fitness was the lowest for aphids that had been feeding on wheat line ‘98-10-19’ for one year. These aphids had the longest development time, and least adult mass, minimal mean relative growth rate, and lowest reproductive fitness. In contrast, the aphids that fed on wheat line ‘98-10-30’ were the fittest, with the shortest development time and highest levels of reproductive fitness. The predatory activities of the ladybeetle, especially the adult male significantly decreased following the consumption of aphids belonging to the ‘98-10-19’-acclimated population. However, there were no significant differences in predatory efficiency (net attack frequency) among the four aphid acclimated populations. Our results showed that the wheat line ‘98-10-19’ has a relative higher resistance to S. graminum than the other three wheat lines, which could further decrease the amount of prey available for consumption. However, the ecological effect of the resistance of ‘98-10-19’ to S. graminum posed no negative influence on the biocontrol potential of P. japonica to these aphids, as their predatory efficiency increases at the fourth instar larvae phase.

Intercropping flowering plants facilitate conservation, movement and biocontrol performance of predators in insecticide-free apple orchard

Habitat management is an important approach suppressing pest via conservation biological control in agricultural systems. Intercropping flowering plants is a well- practiced habitat management measure, supporting predators with shelter, nectar, alternative prey and pollen. However, few studies systematically revealed predator’s conservation performance, transfer process and biocontrol ability by intercropping flowering plants in apple orchards. Here, an experimental model of intercropping flowering plants in apple orchard was planned for two consecutive years to response above questions. Four flowering plants conserve a different number and proportions of six main predator species (three ladybeetles (Propylaea japonica, Harmonia axyridis and Hippodamia variegata), one lacewing (Chrysoperla sinica), one hoverfly (Episyrphus balteatus) and one spider (Misumenops tricuspidatus)). By rubidium (Rb) marking technique, transfer rate of predators C. sinica from flowering plant Cnidium monnieri to apple trees were 79.5 % and 84.1 % in 2020 and 2021, respectively. Transfer rate of predators H. axyridis from flowering plant C. monnieri to apple trees were 74.2 % and 80.1 % in 2020 and 2021, respectively. By predator exclusion trials, the Biocontrol Services Index (BSI) was calculated in sampling date, in which the number of aphids on the caged and uncaged branch has significant difference in the four flowering plants and untreated control plots in 2020 and 2021, respectively. Thus, our results suggest that, intercropping flowering plants in insecticide-free apple orchard contributed to increase the number of predators and biological control of aphid Aphis spiraecola. These findings support that intercropping flowering plants as a promising management option could be implemented in apple orchards.

Analysis of the bacterial communities of four predatory natural enemies collected from a Northern China Bt cotton field

• 16 s RNA sequencing was used to study microbial diversity of four natural enemies. • Harmonia axyridis and Propylaea japonica have the highest microbial diversity. • There are three similar dominant phyla in H. axyridis and P. japonica . • They have 11 common dominant symbiotic bacteria. Predatory natural enemies are major insect species in cotton field ecosystems. Microbes that live inside these insects play essential roles in vital host activities, however, the microbiota of these insects have not been well characterized. In this study, we used Illumina 16S rRNA amplicon sequencing to investigate microbial diversity of the natural enemies Chrysoperla sinica, Harmonia axyridis , Propylaea japonica and Orius similis from a cotton field in northern China. The microbial diversity of C. sinica was low and its dominant bacterial community were Rickettsia (87.78%) and Wolbachia (6.29%). The microbial community of O. similis was more diverse than that of C. sinica . The microbial diversity of H. axyridis and P. japonica was higher, and they had similar dominant phyla, which included Firmicutes, Proteobacteria and Bacteroidetes. Their common dominant bacterial community were Romboutsia , Escherichia-Shigella , Bacteroides , Terrisporobacter , Enterobacter , Lactobacillus , Fusobacterium , Actinobacillus , Sphaerochaeta , Bacteroidales_S24-7_group and Cyanobacteria. This study also forms the basis for further study on the microbiota of natural enemies from different habitats.

Assessment of a zinc finger protein gene (MPZC3H10) as potential RNAi target for green peach aphid Myzus persicae control.

RNA interference (RNAi) has potential application in pest control, and selection of the specific target gene is one of the key steps in RNAi. As an important effector, the zinc finger protein (ZFP) gene has high similarity among aphid species, and may have potential use in an RNAi-based pest control strategy. This study assessed the control efficiency of an RNAi target, MPZC3H10, a CCCH-type ZFP gene, against green peach aphid. ZC3H10 amino acid sequence similarity is more than 97.71% among the five tested aphid species: Myzus persicae, Aphis citricidus, Acyrthosiphon pisum, Diuraphis noxia and Rhopalosiphum maidis. However, no homologous sequence was found in the transcriptome of their ladybeetle predator, Propylaea japonica. Spatial expression patterns revealed that MPZC3H10 showed high expression in the muscle and fat body of M. persicae. The RNAi bioassay revealed that silencing of MPZC3H10 resulted in high mortality (53.33%) in M. persicae. By contrast, there were no observed negative effects on the growth and development of P. japonica when fed on aphids treated with double-stranded RNA (dsRNA) or injected with a "high dose" of dsRNA. Targeting MPZC3H10 showed promising efficiency for green peach aphid control via artificially designed dsRNA, and was safe for the predatory ladybeetle. © 2022 Society of Chemical Industry.

Effects of periodically repeated high-temperature exposure on the immediate and subsequent fitness of different developmental stages of Propylaea japonica.

Repeated extreme high temperature occurs frequently in summer. Propylaea japonica is a predominant predator in South-East Asia and has been considered as a successful natural enemy to control aphids. However, how repeated extreme high temperature affects the fitness of P. japonica remains unclear. This study evaluated the immediate and subsequent fitness of P. japonica when egg, larva, pupa, and adult were exposed to repeated high temperatures (39, 41, or 43 °C for 3h exposure duration per day) during several days. The effect of repeated high temperatures on P. japonica fitness was stage-specific: the egg stage was the most sensitive, the larval and pupal stages were moderately resistant and the adult stage was the most resistant to heat. Repeated high temperatures extended the immature developmental time and decreased the sex ratio of eggs treated with these temperatures, compared to control eggs. A temperature of 39 °C had no significant effect on the pre-oviposition period, oviposition period, fecundity (except stress pupa), or longevity compared with the control, but negative carry-over effects above 39 °C on subsequent stages were found. Repeated high temperature for consecutive days not only had a significant effect on the immediate survival and developmental time, but also had deleterious effects on the subsequent development and performance of P. japonica. The present study provides valuable information for understanding and utilizing P. japonica to control aphids in challenging environments. © 2022 Society of Chemical Industry.

Toxicity of fluralaner against vegetable pests and its sublethal impact on a biocontrol predatory ladybeetle

Fluralaner, a systemic pesticide, was originally registered with the US Food and Drug Administration in 2014 under the trade name Bravecto for flea treatment for pets. As a GABA antagonist, the footprint of fluralaner has expended beyond medical and veterinary pests in recent years. In this study, we examined the acute toxicity of fluralaner against three pests of Henosepilachna vigintioctopunctata, Megalurothrips usitatus, and Phyllotreta striolata in the Solanaceae, Fabaceae, and Cruciferae families, respectively, and the sublethal impact of fluralaner on Propylaea japonica, a widely distributed predatory ladybeetle. Based on LC50, fluralaner was effective against H. vigintioctopunctata (0.098 mg a.i. L−1 for the second instar larvae), M. usitatus (0.134 mg a.i. L−1 for adult females), and P. striolata (0.595 mg a.i. L−1 for adults). For P. japonica, however, fluralaner was substantially less effective (1.177 mg a.i. L−1 for the third instar larvae). Furthermore, the LC10 and LC30 of P. japonica were also consistently higher than the LC50 of the three pests. In addition, we did not observe any significant impacts of fluralaner at LC10 and LC30 on the life history traits, including body weight, developmental time, pre-oviposition period, and fecundity of P. japonica. Based on our results from acute toxicities and sublethal impacts, fluralaner is effective against vegetable pests, while potentially friendly to P. japonica when employed as a biological control agent.

Biological control of Aphis spiraecola in apples using an insectary plant that attracts and sustains predators

Habitat management, such as adding insectary plants to agroecosystems, is a useful technique for biological control. It can improve pest control through natural enemy augmentation and conservation. We evaluated use of the insectary plant Cnidium monnieri (L.) Cuss. to increase the diversity and population density of natural enemies, promote the movement of natural enemies, and improve suppression of the spirea aphid (Aphis spiraecola Patch). An apple orchard experiment included C. monnieri as the treatment and the absence of C. monnieri as the control. The results suggested that C. monnieri can foster predatory natural enemies, such as Propylaea japonica, Harmonia axyridis, Hippodamia variegata, Chrysoperla sinica, and Episyrphus balteata. Density of the predators on the apple trees in the treatment was significantly higher than in the control. Density of spirea aphids on the apple trees in the treatment was significantly lower than in the control. Rubidium (Rb) was used as a tracking marker transferred along the food chain of C. monnieri (4.08 μg/ml) – celery aphid (Semiaphis heraclei) (0.46 μg/ml) – lady beetle (0.51 μg/ml) in a laboratory experiment. The highest Rb content in a lady beetle (0.62 μg/ml) was found 3 days after marking. Combined with field sampling and Rb marking, the results showed that 24.2% and 42.7% of H. axyridis on the apple trees moved from the insectary plant C. monnieri in 2018 and 2019, and that 53.2% and 48.4% of C. sinica on the apple trees transferred from C. monnieri in 2018 and 2019. The insectary plant C. monnieri attracts and fosters predatory natural enemies, which then move to the apple trees and suppress spirea aphids. These findings illustrate an effective method for enhancing biological control of aphids in apple orchards.

Non-crop habitats promote the abundance of predatory ladybeetles in maize fields in the agricultural landscape of northern China

Ladybeetles are promising contributors of biological control services in agricultural landscapes, potentially providing significant economic gains in agricultural production. In northern China, ladybeetles are the most common predators in the annual double-crop rotation system, where the dominant crops are wheat in the spring and maize and cotton in the summer. Land-use features at the landscape level affect ladybeetle populations in a number of ways, and our previous studies have estimated the effects of landscape composition on ladybeetles abundance in wheat and cotton fields in northern China. However, these landscape effects on ladybeetle abundance in maize remain insufficiently documented in this specific agro-ecosystem. We assessed the relationships between ladybeetle abundance and landscape composition at four spatial scales (0.5, 1.0, 1.5, and 2.0 km) in a summer maize system at the whorl stage (the main period for ladybeetle colonization). We found that both semi-natural habitats (woodlots and grasslands) and vegetation around water bodies increased the abundance of ladybeetles in maize fields, and maize area played a dilution effect on ladybeetle abundance in this crop. These non-crop habitats might serve as source of emigrants that disperse to maize fields. The smallest scale (0.5 km) studied was the most predictive spatial scale in this colonization period for ladybeetles. Propylaea japonica, the dominant ladybeetle, showed response to landscape variables in a similar way as the whole ladybeetle population did. These findings suggest that leaving some non-crop habitats and reducing human disturbance to this vegetation within a landscape will enhance ladybeetle abundance in maize fields. Consistent with our previous studies in wheat and cotton fields in the same system, maintaining the continuity in time and space of functional habitats was essential for the persistence of ladybeetle populations within the landscape. In the future, habitat management and landscape design to ensure resource continuity should be encouraged to maximize the conservation of ladybeetles in agricultural ecosystems in northern China.

Vitality and Stability of Insecticide Resistance in Adult Propylaea japonica (Coleoptera: Coccinellidae).

Propylaea japonica (Thunberg) was a dominant species among the predacious ladybirds in the fields and active from March to November during a year in Fuzhou, China. Stability of insecticide resistance and vitality in adult P. japonica were investigated. The field ladybird P. japonica in Fuzhou, China, showed 9- to 16-fold resistance ratios to chlorpyrifos, 13- to 2,083-fold to methamidophos, 32- to 230-fold to fenvalerate, and 4- to 49-fold to avermectins, respectively, based on the field monitoring during 2004, 2009, and 2012, as compared with insecticide-susceptible F39 progenies. The resistance levels in the field P. japonica were high during May and November but low during summer. The population growth tendency index in field P. japonica was 0.8-fold as high as that in insecticide-susceptible P. japonica. The field P. japonica also showed high tolerance to the insecticide as compared with pest Lipaphis erysimi Kaltenbach and two parasitoids Diaeretiella rapae and Pachyneuron aphidis. Stable insecticide resistance levels and high vitality were found first in adult P. japonica with 1-, 30-, or 60-d-old adults, or among the adults developed form the eggs produced by newly emerged adults or by 60-d-old adults. Increased activity of glutathione S-transferases, carboxylesterases, and cytochrome P450 monooxygenases might be involved in the resistance of P. japonica. The results indicated that, in certain areas, inclusion of P. japonica for pest control in the integrated pest management would be highly recommended.

Field Trapping of Predaceous Insects With Synthetic Herbivore-Induced Plant Volatiles in Cotton Fields

Nine herbivore-induced plant volatiles (HIPVs) and one methyl jasmonate were field-tested for their attractiveness to the main predators in cotton fields of North China in 2 yr. The main predators including ladybird beetles (Propylaea japonica (Thunberg), Harmonia axyridis (Pallas)), green lacewings (Chrysoplera sinica (Tjeder), Chrysopa spp.), predatory bugs (Geocoris pallidipennis (Costa), Orius spp., Nabis spp.) and spiders (Misumenops tricuspidatus (Fabricius), Erigonidium graminicolum (Sundevall)) were investigated. Two-way ANOVA indicated that the volatile compound, year, and the volatile compound × year interaction affected the behavioral responses of predators. It was found that indole significantly attracted the ladybird beetle P. japonica, H. axyridis. Linalool could attract P. japonica. Green lacewing C. sinica was significantly attracted by α-pinene and β-pinene, whereas indole significantly attracted Chrysopa spp. Methyl jasmonate and α-pinene showed significant attraction to small-flower bug Orius spp. In addition, the attraction of α-humulene to C. sinica, attractiveness of β-pinene to Orius spp. and Chrysopa spp., were observed only in one of the two years. However, the big-eyed bug G. pallidipennis, damsel bug Nabis spp., spiders M. tricuspiata and E. graminicolum did not respond to any of the tested HIPVs. These results are discussed with respect to possible applications of a synthetic attractant for main predators in cotton fields.

Identification and characterization of ace1-type acetylcholinesterase in insecticide-resistant and -susceptible Propylaea japonica (Thunberg).

Characterization and gene cloning of acetylecholinesterase (AChE) in the insecticide-resistant (R) and -susceptible (S) insects have been reported in the past. However, the studies focused mostly on herbivorous pests, rather than predacious species, such as ladybird beetles. Using R and S Propylaea japonica (thunberg), a full-length cDNA sequence (2928 bp) of the ace1-type AChE gene was determined for the first time. The ace1 encoding a protein of 645 amino acids contained typical conserved motifs, such as FGESAG domains, catalytic triad, acyl pocket, oxyanino hole, choline binding site, peripheral anionic site, omega loop and conserved aromatic residues. R P. japonica displayed 50-times greater resistance to chlorpyrifos or mathamidophos with a significantly lower AChE sensitivity to paraoxon, malaoxon, chlorpyrifos or methamidophos than its S counterpart. Five amino acids in the ace1 of R P. japonica differed from those found in S P. japonica. One of them, F358S, located in the acyl-binding pocket, might play a crucial role in the resistance of the insect to organophosphates (OPs). Whereas, K493E and I538V, which were close to some of the conserved aromatic amino acids (i.e., H509, Y511, and W499) in the gorge, and G571R and T576A near C593 that formed the disulfide bonds with C471, might also involve in the change of insecticide resistance in P. japonica. AChE insensitivity and amino acid replacements, particularly F358S, might be the determining factors in the alteration of OPs-resistance in P. japonica.

Insecticide susceptibility of the green plant bug, Apolygus lucorum Meyer-Dür (Homoptera: Miridae) and two predatory arthropods

Abstract The green plant bug (Apolygus lucorum Meyer-Dür) is a key pest of Bt cotton in China. Along with biological control, chemical control is one of the most important strategies in A. lucorum Integrated Pest Management (IPM). The goal of this study was to evaluate the toxicity of eight conventional insecticides to A. lucorum and to assess the susceptibility of two generalist predators Chrysopa sinica (Jieder) and Propylaea japonica (Thunbery) to insecticides that are commonly used in A. lucorum management. Via glass-vial and leaf-dip bioassay, toxicity tests with selected insecticides at two different life-stages of A. lucorum indicated significant differences between the LD50 or LC50 values for these compounds within different insecticidal classes. Phenylpyrazole fipronil had the highest toxicity to 4th-instar nymphs and adults of A. lucorum, whereas neonicotinoid imidacloprid had the lowest toxicity among the insecticides. Females were more tolerant to insecticides than were males, as shown by the higher LD50 values for females. Furthermore, laboratory tests showed that endosulfan had the highest selectivity to C. sinica and P. japonica: the selective toxicity ratios (STRs) were superior to other tested insecticides, particularly imidacloprid, and were 5.396 and 4.749-fold higher than baseline STRs, respectively. From this study, we conclude that fipronil can potentially be used to efficiently control A. lucorum. An alternative control agent worth consideration is endosulfan, owing to its relative safety to non-targeted natural enemies.

The effects of transgenic Cry1Ac+Cry2Ab cotton on cotton bollworm control and functional response of predators on whitefly

In this study, we detected and clarified the roles of transgenic Cry1Ac+Cry2Ab cotton "639020" in controlling cotton bollworm (Helicoverpa armigera) during critical periods of bud stage (second generation of bollworm), flowering stage (third generation of bollworm) and bolling stage (fourth generation of bollworm) as well as the influences of 639020 cotton on functional response of the main predators (Chrysopa sinica larvae, Propylaea japonica, Orius and Erigonidium graminicola ) on whitefly using transgenic Cry1Ac cotton "CCRI41" and conventional cotton "CCRI49" as the control. Our results showed that the 639020 cotton well controlled the second and third generation of bollworm, and the level of insect resistance increased by 52.85% and 16.22% separately compared with that of CCRI41, with a significant effect on the second generation of bollworm. Moreover, the number of bollworm eggs in 639020 cotton field was lower than that in CCRI41 and CCRI49 cotton fields (except the second generation of bollworm) during the cotton bud, flowering and bolling stages. Although the number of bollworm larvae in 639020 cotton field was significantly lower than that in CCRI49 field, and both under the controlling index, it has no significant difference compared with that in CCRI41 cotton field. There were also no obvious changes in predator functions of Chrysopa sinica, Propylaea japonica, Orius and Erigonidium graminicola on bemisia tabaci between 639020, CCRI41 and CCRI49 cotton filed. This study evaluated the safety of new transgenic cotton on environment, anti-insect activity of exogenous gene and the safety of production and application prospect.

Antioxidant responses of Propylaea japonica (Coleoptera: Coccinellidae) exposed to high temperature stress

Temperature is one of the most important environmental factors, and is responsible for a variety of physiological stress responses in organisms. Induced thermal stress is associated with elevated reactive oxygen species (ROS) generation leading to oxidative damage. The ladybeetle, Propylaea japonica (Thunberg) (Coleoptera: Coccinellidae), is considered a successful natural enemy because of its tolerance to high temperatures in arid and semi-arid areas in China. In this study, we investigated the effect of high temperatures (35, 37, 39, 41 and 43°C) on the survival and activities of antioxidant enzymes, including superoxide dismutase (SOD), catalase (CAT), peroxidases (POD), glutathione-S-transferases (GST), and total antioxidant capacity (TAC) as well as malondialdehyde (MDA) concentrations in P. japonica adults. The results indicated that P. japonica adults could not survive at 43°C. CAT, GST and TAC were significantly increased when compared to the control (25°C), and this played an important role in the process of antioxidant response to thermal stress. SOD and POD activity, as well as MDA, did not differ significantly at 35 and 37°C compared to the control; however, there were increased levels of SOD, POD and MDA when the temperature was above 37°C. These results suggest that thermal stress leads to oxidative stress and antioxidant enzymes play important roles in reducing oxidative damage in P. japonica adults. This study represents the first comprehensive report on the antioxidant defense system in predaceous coccinellids (the third trophic level). The findings provide useful information for predicting population dynamics and understanding the potential for P. japonica as a natural enemy to control pest insects under varied environmental conditions.

捕食者对空心莲子草叶甲种群的生物胁迫

Generalist predators are often applied in biological control of pests. Sine generalist predators often prey on herbivorous insects unselectively,they also influence biological control of weeds with herbivorous insects. The alligator weedflea beetle,Agasicles hygrophila( Coleoptera: Chrysomelidae) is acted as a specific biological control of the alligator weed Alternanthera philoxeroides( Amaranthacese: Alternanthera),and it had been introduced to China from Florida,USA. It has performed a good control effect on A. philoxeroides since the beetle was released in the areas invaded by A. philoxeroides. Although the population of A. hygrophila had been established and spread to adjacent regions from the release sites,the population abundance of the beetle maintains only a lower level. Thus,it can not suppress effectively the population expansion and spread of A. philoxeroides. We found that many generalist predator species such as spiders and predatory insects live in the habitat of A. philoxeroides. Whether the generalist predators are a biotic stress factor for suppressing the population expansion of the beetle? To demonstrate this problem,a predator-prey system including predators,i. e. lady beetle Propylaea japonica( Coleoptera: Coccinellidae),spider Oxyopes sertatus( Araneae: Oxyopidae) and Pirata subpiraticus( Araneae: Lycosidae),and host preys,i. e. egg,1st—3rdinstar larva and adult of A. hygrophila was built. Then the daily eating number of the above three predators on different immature stages and adults of A. hygrophila was observed in the laboratory. This aim to understand the biotic stress of predators on A. hygrophila in a natural ecosystem that may evaluate objectively the biological control efficiency of A. hygrophila on A. philoxeroides in the field. The results showed that P. japonica,O. sertatus and P. subpiraticus could feed on eggs as well as 1st—2ndinstar larvae of A. hygrophila. Both O. sertatus and P. subpiraticus could feed on 3rdinstar larvae of A. hygrophila. The predatory capacities of P. japonica, O. sertatus and P. subpiraticus to eggs and larvae of A. hygrophila increased,but searching efficiency of the predators decreased with the increasing densities of prey. However,the three predators did not prey on adult A. hygrophila in this experiment. The predatory function responses of P. japonica and P. subpiraticus on eggs,1st—2ndinstar larvae,and of O. sertatus on eggs,1st—3rdinstar larvae of A. hygrophila fitted to the disc equation of Holling II. With the exception of the predatory function response of P. subpiraticus on 3rdinstar larvae of A. hygrophila,there were a significant correlation between predator and host prey that were fitted by the disc equation of Holling II. The maximum theoretical number of eggs, 1stinsar and 2ndinsar larvae of A. hygrophila captured by O. sertatus,P. subpiraticus and P. japonica per day was 10.9,6.2 and 5.6 eggs,17.1,35.8 and 10.4 1stinsar larvae,and 6.6,11.2 and 2.9 2ndinsar larvae,respectively. The maximum theoretical number of 3rdinsar larvae of A. hygrophila captured by O. sertatus and P. subpiraticus was 12.3 and 1.1 larvae, respectively. The results of our present study suggest that the predation of predators can decrease the population density of A. hygrophila,which weakens the control efficiency of A. hygrophila on A. philoxeroides in the field. Therefore,the predators are an important biotic stress factor that affects survival and development of A. hygrophila in the field. Another further study should focus on how the biocontrol efficiency of A. philoxeroides are enhanced via increasing the population density of A. hygrophila in the field.

Insect predators in northeast China and their impacts on Aphis glycines

AbstractPredators of Aphis glycines Matsumura (Hemiptera: Aphididae) were surveyed and their ability to suppress A. glycines population growth was determined in Harbin, northeast China (45.4°N, 126.4°E). Field surveys were conducted on 21 fixed sampling sites in 2004 and 17 in 2005. Impacts of natural enemies of A. glycines were studied using exclosure experiments. Thirteen natural enemies were found, the most abundant of which was Propylaea japonica (Thunberg), Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae), Chrysopa sinica Tjeder, Chrysopa phyllochroma Wesmael, Chrysopa formosa Brauer (Neuroptera: Chrysopidae), Hemerobius humuli Linnaeus (Neuroptera: Hemerobiidae), Orius Wolff sp. (Heteroptera: Anthocoridae), Nabis stenoferus Hsiao (Heteroptera: Reduviidae), Deraeocoris punctulatus (Fallén) (Heteroptera: Miridae), and Episyrphus balteata (De Geer) (Diptera: Syrphidae). Three exclosure treatment types were established, large-mesh cages, small-mesh cages, and no cages. In exclosures, A. glycines density in small-mesh cages peaked at numbers 3.75-fold higher than in large-mesh cages and 17.44-fold higher than on plants with no cages in 2004. In 2005, these numbers were 4.59-fold and 60.98-fold. Temperature was not a factor in exclosures, but relative humidity had significant effects. These results indicated that existing predator communities could partially suppress soybean aphid population density in soybean fields in northeast China.

Influence of five aphid species on development and reproduction of Propylaea japonica (Coleoptera: Coccinellidae)

Propylaea japonica is one of the most promising biological control agents in northern China. The objectives of the present study were to investigate the preimaginal development, immature survival, reproduction, longevity and fecundity of the ladybeetle, P. japonica, when reared on five different aphids species, Aphis gossypii Glover, Myzus persicae (Sulzer), Aphis craccivora Koch, Acyrthosiphon pisum (Harris) and Chaitophorus populeti (Panzer) and to quantify their relative suitability as prey. The results of the study indicate that the pre-adult development was shorter (9.9±0.1days) when fed on A. craccivora but was the longest (13.5±0.2days) on A. pisum. Immature survival, adult emergence, growth index, development rate, male and female longevity, oviposition period, and fecundity were maximal when P. japonica were fed on A. gossypii. In contrast these biological parameters were minimal on A. pisum. The ladybird adult’s fresh weight was maximal after feeding on A. gossypii and minimal on A. pisum. Further analysis revealed linear relationships between rate of development and weight of adult females; and longevity and fecundity of adult females. The results of the present study suggest the order of suitability of aphid species for P. japonica is A. gossypii>A. craccivora>M. persicae>C. populeti>A. pisum. The present study further propose that either the mass-rearing of P. japonica in the laboratory can be carried out by supplying the best food or the understanding its relative abundance in the field in relation to the availability of different prey species.

雨花露水蜜桃主要害虫与其捕食性天敌的关系

To conserve and utilize natural enemies for comprehensive control of insect pests in peach orchards,the seasonal and annual variations of population quantities of the five kinds of insect pests with their natural enemies were systematical investigated in the Yuhualu juicy peach orchard.The findings of a paired t-testing demonstrated that the t values of five kinds of main pest numbers,i.e.Empoasca flavescens,Myzus persicae,Tetranychus viennensis,Cleoporus variabilis and Stephanitis nashi,indicating that no significant differences existed in the numbers of five kinds of insect pests in Yuhualu juicy peach orchard between the two spring-summer seasons of 2010 and 2011.Whilst the t values of the seven kinds of natural enemy numbers,i.e.Erigonidium graminicola,Misumenops tricuspidatus,Theridion octomaculatum,Clubiona japonicola,Propylaea japonica,Chrysopa sinica and Epistrophe balteata,all were significantly lower than 2.16(t0.05 value),revealing that there were also no significant differences in the numbers of the seven kinds of natural enemies between the two spring-summer seasons of 2010 and 2011.Surprisingly,the t value of Harmonia axyridis was 2.39 2.16(t0.05 value),showing that the difference in numbers was significant between the two spring-summer seasons of 2010 and 2011.The further analysis indicated that the t values of Empoasca flavescens,Stephanitis nashi,Misumenops tricuspidatus,Harmonia axyridis,were,respectively,5.63,76.38,3.28 and 4.82 3.01(t0.01),indicating that there were significant differences in their numbers in Yuhualu juicy peach orchard between the spring-summer season and the autumn season of 2010,whereas no significant differences existed in the others.Moreover,the quantity,time and space framework of Myzus persicae,Empoasca flavescens,Tetranychus viennens,Cleoporus variabilis,Stephanitis nash and their predatory natural enemies in 2010 spring-summer season and autumn season,as well as 2011 spring-summer season were systematically studied using grey system analysis,ecological niche analysis and aggregated-intensity index analysis of spatial patterns.The synthetic ranking results indicated that,in 2010 spring-summer season,the orders of main natural enemies of Empoasca flavescens were Misumenops tricuspidatus,Chrysopa Sinica and Theridion octomaculatum,whereas the ranks of main natural enemies of Tetranychus viennensis were Clubiona japonicola,Theridion octomaculatum and Erigonidium graminicola.In 2011 spring-summer season,the orders of main natural enemies of Myzus persicae,Empoasca flavescens,Cleoporus variabilis,Stephanitis nashi and Tetranychus viennensis,were,respectively,Epistrophe balteata,Harmonia axyridis and Misumenops tricuspidatus;Erigonidium graminicola,Propylaea japonica and Misumenops tricuspidatus;Erigonidium graminicola,Misumenops tricuspidatus and Theridion octomaculatum;Misumenops tricuspidatus,Propylaea japonica and Erigonidium graminicola;Clubiona japonicola,Theridion octomaculatum and Erigonidium graminicola.In 2010 autumn-winter season,the ranks of main natural enemies of the Empoasca flavescens and Stephanitis nashi,were,respectively,Chrysopa Sinica,Erigonidium graminicola and Misumenops tricuspidatus;Theridion octomaculatum,Erigonidium graminicola and Misumenops tricuspidatus.The further analyses showed that the average λ values of Empoasca flavescens,Stephanitis nashi and Tetranychus viennensis in 2010,and Myzus persicae,Cleoporus variabilis,Stephanitis nashi and Tetranychus viennensis in the spring-summer season of 2011 all are more than 2,and in the four different directions of peach tree crown,the λ value of Tetranychus viennensis in the 2010 spring-summer season,and Empoasca flavescens in the 2010 autumn-winter season,as well as Cleoporus variabilis in the 2011 spring-summer season all are also more than 2,suggesting that the gathering cause of the insect pests resulted from themselves.However,the λ values of the other insect pests and natural enemies all were less than 2,indicating that their gathering was caused by certain environment factors.

Effects of plant trichomes on herbivores and predators on soybeans

Abstract Tritrophic interaction in soybean system has received increasing attention recently. However, few studies have investigated the influence of plant trichomes on the population dynamics of soybean herbivores and their natural enemies. We conducted a field survey to investigate whether soybean trichomes affected the abundance of herbivores and their predators. The results of this study show that moderately or densely pubescent trichomes have positive influences on the abundance of some herbivores (e.g., Stollia guttiger) and predators (e.g., Propylaea japonica and Orius similes) although the influence may change over time, while trichome types do not affect the density of soybean aphid, Aphis glycines.