Efficacy of Beauveria bassiana (Blas.) Vuill. against cabbage aphid Brevicoryne brassicae L. (Hem.: Aphididae) in laboratory condition

In order to replace the conventional chemical pesticides, extensive researches have been done on entomopathogenic fungi. Entomopathogenic fungus Beauveria bassiana is an important biocontrol agent against major economic pests and is being employed in Integrated pest management (IPM) along with synthetic pesticides. Cabbage aphid Brevicoryne brassicae L. is one of the important pests of Brassicaceae family. Therefore, in this research, the virulence isolate of B. brassicae (IRAN 429C) was investigated on adults of cabbage aphid under laboratory conditions. The experiments were conducted at 25 ± 2 °C, 60 ± 10 R. H. and a photoperiod of 16:8 (L: D). After preliminary experiments, the adult aphids were treated with fungal concentrations of 1 × 10³ to 1 × 10⁷ spores/ml. Probit analysis was conducted to calculate LC₅₀ and LC₉₅ values for the isolate. Positive correlation was observed between concentrations and pest mortality. LC₅₀ and LC₉₅ values calculated for IRAN 429C isolate are 2.04 × 10⁵ and 1.82 × 10⁸, respectively. The mortality was counted one day after the treatment and then continued for 14 days. Cumulative mortality for 14 days after treatment varied from 54% for IRAN 429C at low concentration (10³ conidia/ml) to 83% at high concentration (10⁷ conidia/ml). The lowest LT₅₀ was obtained at 7.67 days for IRAN 429C isolate at concentration 1 × 10⁷ spore/ml. According to the insecticidal activity of mentioned fungi on cabbage aphid, it can be used in biocontrol programmes of B. brassicae.     

The fine structure of distal receptors on the labium of the aphid,Brevicoryne brassicae L. (Homoptera)

Summary Short peg receptors located at the distal tip of the aphid labium have the structure of mechanoreceptors. Each peg is innervated by a single sensory nerve which is anchored eccentrically to a basal cuticular tube and terminates in electron-dense material in the base of the peg. The arrangement and eccentric insertion of the eight pegs in the labial wall on one side of the stylet groove, with the eccentric insertions of their innervating neurones, provide a mirror image of the receptors on the opposite side. On the basis of a comparison of the structure of these receptors with that of tactile receptors for which electrophysiological data on sensitivity are available, it is possible to predict that the receptors detect both surface contact (pressure) and surface profile; and that the bilateral symmetry in the receptor arrangement facilitates the detection of vein contours which are preferred settling sites on the leaf. The structure of the dendritic terminal and its insertion is that of a well reinforced cytoskeleton designed to transmit tension to the cell membrane, in agreement with the concept that transduction is a membrane related phenomenon. The distal microtubules, fifty per-cent of which originate as well as terminate in the tubular body, are packed in electron-dense material which binds to the cell membrane. The membrane in turn is attached to cuticular components of the receptor. Abrupt changes in dimension of the dendritic outer segment may be designed to modulate the conduction of a membrane potential. On the other hand, lack of continuity in the microtubules makes these organelles poor candidates for the transduction of excitation from a distal site of stimulation to a proximal region.Supported by operating grants Nos. A 6063 and A 9856 from NRCC     

Population fluctuations of cabbage aphid,Brevicoryne brassicae (L.) (Hom.: Aphididae) and its natural parasitism rate on different canola cultivars

The cabbage aphid, Brevicoryne brassicae is one of the most destructive pests in Cruciferaceae or Brassicaceae plant family around the world. According to this pest rapid resistance to insecticide, using the resistant cultivars should be evaluated. In the present study, the different canola cultivars resistance against the cabbage aphid and the population fluctuations in canola fields and also the natural parasitism are evaluated in Shahre-rey region. To evaluate the population fluctuations and its natural parasitism on the RGS003, SLMOO46, Karag2, Licord, Sarigol, Opera, Ocapi and Talaei canola cultivars were cultivated in four replications using the complete randomised block design. The population fluctuations studies showed that the pest is active during the canola growth period in studied region, but the peak of population and damage is found in 6 May month. The results showed that natural parasitism percentage of cabbage aphid on different canola cultivars has not significant difference, but the parasitism amount in different sampling dates was significantly different, so that the natural parasitism maximum observed in date 29 April. These results showed that the different canola cultivars have significant effects on cabbage aphid and parasitoids activity amount. Using the present results, the recognised cultivars in integrated pest management programmes can be used to grow the laboratory aphids as the parasitoids hosts.     

Sub-lethal effects of tiametoxam on life table parameters of the cabbage aphid,Brevicoryne brassicae (L.) (Hemiptera: Aphididae) under laboratory conditions

Efficiency of tiametoxam was determined on population growth parameters of cabbage aphid, Brevicoryne brassicae L. (Hemiptera: Aphididae) using demographic toxicology by leaf spray method. At first, bioassay was performed. The LC₅₀ values and confidence limits for thiamethoxam were 169.05?ppm (92.61–342.51). To evaluate, the sub-lethal effect of this insecticide on population growth parameters of cabbage aphid, LC₂₅ and LC₁₀ concentrations of tiametoxam were used at 58.8 and 22.05?ppm, respectively. Also, the LC₅₀ value of insecticide on the life table estimates was measured. Experiments were carried out in the laboratory at 23?±?1?°C, 60?±?5% RH and 16:8 (L:D) photoperiod on cabbage seedlings, Brassica oleracea, var. capitata L. Net fecundity rate decreased in insecticide-treated populations. Intrinsic rates of increase (r_m) were lower in tiametoxam treatment than in controls. There was a relative increase in intrinsic death rates of treated populations. The mean generation time and doubling time were also lower in population treated with insecticide than the control. There was a considerable reduction in the average numbers of nymphs reproduced per female as compared with the control. The average longevity of female adults in the control was significantly different (p?<?0.05) from those treated with thiamethoxam.     

Population growth parameters of the cabbage aphid,Brevicoryne brassicae (L.) (Hemiptera: Aphididae), exposed to sublethal doses of thiacloprid

The cabbage aphid, Brevicoryne brassicae L. (Hemiptera: Aphididae) is a major pest of cabbage in the world. In this study, the influence of thiacloprid on population growth parameters of B. brassicae using demographic toxicology by leaf spray method was determined. The LC₅₀ values and confidence limits for thiacloprid were 274.89?ppm (185.22–479.22), respectively. To evaluate the sublethal effect of this insecticide on population growth parameters of cabbage aphid, LC₂₅ and LC₁₀ concentrations of thiacloprid were used at 76.44 and 23.52?ppm, respectively. Also The LC₅₀ value of this insecticide on the life table estimates was measured. Experiments were carried out in the laboratory at 23?±?1?°C, 60?±?5% RH and 16:8 (L:D) photoperiod on cabbage seedlings, Brassica oleracea, var. capitata L. Intrinsic rates of increase (r_m) were lower in thiacloprid treatment than in controls. The mean generation time and doubling time were also lower in populations treated with insecticide than in controls. There was a considerable reduction in the average numbers of nymphs reproduced per female as compared with the control. The average longevity of female adults in the control was significantly different (p?<?0.05) from those treated with thiacloprid. According obtained results, thiacloprid is a good choice for control of the B. brassicae.     

Effect of eight cauliflower cultivars on biological parameters of the cabbage aphid,Brevicoryne brassicae (L.) (Hem: Aphididae) in laboratory conditions

The cabbage aphid, Brevicoryne brassicae is one of the most important pests with broad host range that does damage to cruciferae plants. In this research, biology parameters of the cabbage aphid was studied on the eight cauliflower cultivars: Smilla, Snow mystique, White cloud, Buris, Galiblanka, Snow crown, SG and Tokita. This study was conducted under controlled conditions (25?±?2?°C, 65?±?5% RH and L-D: 16–8). Statistical analysis showed that there is significant difference between different stages of growth and mean number of laid nymphs period (p?<?0.05), so that the maximum and minimum growth period were observed on the cultivars Galyblanka and Buris, respectively. The longest mean longevity of total nymphal instars was obtained on White cloud, and the shortest on Smilla. The highest pre nymph period, nymph production period, mean number of laid nymphs, Adult longevity and total lifespan on the Galiblanka cultivar was calculated as 8.60, 13.50, 58.60, 17.30 and 25.90, respectively. The results showed that using cultivars that affected on the adult reproductive parameters and provides conditions for reduction of reproduction could be a good solution for the cabbage aphid control management.     

Resistance of rape (Brassica napus) to attack by the cabbage aphid (Brevicoryne brassicae L.)

Resistance to Brevicoryne brassicae L. attacks in a New Zealand variety of forage rape resulted from a combination of host non–preference and antibiosis. Using clonal plant material obtained from cuttings, only half the numbers of immigrant alate cabbage aphids that settled to reproduce on the susceptible rape were to be found on the resistant rape. The reproduction rate of these alates was about 12 % slower on the resistant plants than on the susceptibles and the young took about 13% longer to mature. Antibiosis then shortened the reproductive life of the apterae by one-third, reduced their fecundity by nearly 50 % and caused 40% mortality in their progeny. The over-all effect of this was considerable and under conditions specified in the text could result in the population on the resistant plants being about one-eighth that on the susceptible plants in under 1 month. The resistant plants lost their resistance on flowering and became normally susceptible to cabbage aphid attack. With maturity, however, the B. brassicae-resistant plants became slightly resistant to Myzus persicae.     

Temperature and host plant effects on development and fecundity of Brevicoryne brassicae (L.) (Homoptera: Aphididae)

The development, survival and reproduction of the cabbage aphid, Brevicoryne brassicae (L.) were evaluated at three constant temperatures (20, 25 and 30°C) on cabbage, cauliflower, red cabbage, turnip and radish. The development periods of immature stages ranged from 10.7 d at 20°C to 7.60 d at 30°C for red cabbage. Total percentages of survivorship of immature stages varied from 39.40 and 82.50 within the temperature range of 25–30°C on radish. The average progeny per female was 31.15, 28.95 and 23.77 at 20, 25 and 30°C on cabbage.     

Purification and characterisation of a non-plant myrosinase from the cabbage aphid Brevicoryne brassicae (L.)

Plant myrosinases and glucosinolates constitute a defence system in cruciferous plants towards pests and diseases. We have purified for the first time a non-plant myrosinase from the cabbage aphid Brevicoryne brassicae (L.) to homogeneity. The protein was N-terminally blocked and protease (trypsin and lys c) degradation gave peptides of which five were sequenced. The protein is a dimer with subunits of mass 54 kDa+/-500 Da. Western blot analysis with an anti-aphid myrosinase antibody showed a strong cross reaction with a protein extract from the Brassica specialist, B. brassicae. The anti-aphid myrosinase antibody does not cross react with plant myrosinase neither does an anti-plant myrosinase antibody cross react with aphid myrosinase.     

Winter ecology of the cabbage aphid Brevicoryne brassicae (L.) (Homo., Aphididae) and its parasitoid Diaeretiella rapae (McIntosh) (Hym., Braconidae: Aphidiidae)

Abstract:  Flower strips near crops may stimulate natural enemies by the provision of nectar and hibernation sites. However, these habitats may also be beneficial for potential pest species. We investigated the dynamics of the cabbage aphid Brevicoryne brassicae (L.) (Homo., Aphididae) and its primary parasitoid Diaeretiella rapae (McIntosh) (Hym., Braconidae) in brussels sprout fields and adjoining flower plots in winter. A wide variety of 14 plant species were included in the study, each established as monoculture plots. Brussels sprout fields and flower plots were established at two sites. One site was located in an open agricultural landscape, the other in a landscape dominated by mixed forest. Brevicoryne brassicae and D. rapae were found on brussels sprout plants but not in the flower plots. Brevicoryne brassicae was initially more abundant in the open landscape, but as their densities declined rapidly in time, no living aphids were recovered at both sites by February. The density of aphids parasitized by D. rapae showed a similar trend, but densities of eight mummies per brussels sprout plant were still present by the end of February. These findings suggest that (i) flower species under investigation do not function as sources of B. brassicae and (ii) brussels sprout plants that are not harvested may not only harbour D. rapae populations that may sustain biological control, but are also likely to act as sources of B. brassicae infestation.     

Characterization and evolution of a myrosinase from the cabbage aphid Brevicoryne brassicae.

The aphid myrosinase gene has been elucidated using Rapid Amplification of cDNA Ends-PCR. Sequencing has shown that aphid myrosinase has significant sequence similarity (35%) to plant myrosinases and other members of glycosyl hydrolase family 1 (GHF1). The residues acting as proton donor and nucleophile, in the hydrolysis of glucosinolates by aphid myrosinase, are identified as Glu 167 and Glu 374 respectively. The equivalent residues in plant myrosinase are Gln 187 and Glu 409 and for the cyanogenic beta-glucosidase Glu 183 and Glu 397. Thus it would appear that the absence of a proton donor is not necessary for the hydrolysis of glucosinolates as was thought to be the case for the plant myrosinases. Aphid myrosinase appears to be more similar to animal beta-O-glucosidases than to plant myrosinases, as assessed by sequence similarity and phylogenetic techniques. These results strongly suggest that myrosinase activity has twice arisen from beta-O-glucosidases in plants and animals. Comparison of aphid myrosinase with plant myrosinase has highlighted Lys 173 and Arg 312 as possibly playing a crucial role in the hydrolysis of glucosinolates by aphid myrosinase.     

Serological Detection of Beet Western Yellows Luteovirus in the Non-vector,Brevicoryne brassicae (Homoptera: Aphididae)

The interaction between beet western yellows luteovirus (BWYV) and the aphid species Brevicoryne brassicae was investigated using virus transmission and serological detection experiments. This species failed to transmit a BWYV isolate from infected to healthy oilseed rape plants, although virus was readily detected by double-antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) in single B. brassicae adults. When virus-carrying adults were tested by ELISA after different inoculation access periods, the number of virus-positive individuals decreased after 5 days, whereas with the efficient vector Myzus persicae, virus-positive individuals were found even after 10 days. This confirms the inability of B. brassicae to transmit BWYV, even though it may acquire the virus. It is suggested that B. brassicae, as compared with the efficient vector M. persicae, may serve as an experimental model for studying the mechanisms of the luteovirus-vector specificity     

甘蓝蚜寄生蜂及其应用

本文就甘蓝蚜的寄生蜂种类、生物学特性、寄主选择特性、农药对寄生蜂的影响及寄生蜂在生物防治中的应用等方面的研究进展进行了较全面的综述。     

Field evaluation of aqueous extract of Melia azedarach Linn. seeds against cabbage aphid,Brevicoryne brassicae Linn. (Homoptera: Aphididae), and its predator Coccinella septempunctata Linn. (Coleoptera: Coccinellidae)

Aqueous extract of Melia azedarach seeds were tested against cabbage aphid, Brevicoryne brassicae, and its predator Coccinella septempunctata in a cabbage field. The field experiment was conducted at Bridge to Israel children village farm, around the vicinity of Tewodros campus, University of Gondar, where the cabbage was grown fully organically. A field experiment was started in the middle of April 2011 and completed at the end of May 2011. The experiment was conducted in a randomised block design (RBD). For the field trial, a total of 12 plots were prepared with 1 m² area for data collection. The powdered M. azedarach seeds were used to prepare 5% concentration of aqueous solution and sprayed. Before spraying, percentage of aphid infestation was recorded from the control plot and the experimental plot. The average percentage of cabbage infestation in the control plot was 72% and in the experimental plot before treatment was 80.85%. The percentage reduction of aphid population was 19.06% after the first spraying. However, maximum percentage reduction of 86.5% was recorded after the completion of six-week treatment. The overall percentage reduction increased proportionately from the first to sixth week. The number of predator population was reduced and the reduction was not statistically significant (p > 0.05). The present study proved that Melia seed extracts were effective against cabbage aphids under field condition. Further, it is evident that the beneficial interaction between botanical extracts and biological control organism in the field showed safety to natural enemies. In conclusion, Melia seed extract can be useful for small-scale farmers to protect their cabbage crop against cabbage aphid, B. brassicae.     

The influence of genetic background on resistance to the cabbage aphid (Brevicoryne brassicae) in Kale (Brassica oleracea var. acephala)

Resistance to Brevicoryne brassicae has been identified in the progeny of two selected kale (B. oleracea var. acephala) plants, one from the F1 hybrid cultivar ‘Arsis RS’ and one from the landrace ‘Butzo’. These plants were crossed with susceptible B. oleracea morphotypes that have different periods to flowering. The type of susceptible plant line used had an effect on the resistance phenotypc of the progeny. Tested F2 populations derived from these crosses show that resistance is not under simple genetic control. This, in addition to variation in aphid numbers within accessions, suggests that separation of genetic components of control from environmental ‘noise’ for any accession may only be possible by the production of double haploid plant lines.     

Zinc and cadmium accumulation in cabbage aphid (Brevicoryne brassicae) host plants and developmental instability

Developmental instability in morphological characters can occur during individual development due to various environmental stresses. Fluctuating asymmetry (FA) is often used as a measurement of developmental instability, but within-environment variation (CV_e) is also considered an indicator of developmental instability. Cabbage aphid ( Brevicoryne brassicae ) populations were reared on zinc- (Zn) or cadmium- (Cd) contaminated cabbage and radish plants. Developmental instability indicators were measured and their relations with fitness were explored. Results revealed that cabbage aphids exposed to Cd and Zn displayed considerable developmental instability, particularly fluctuating asymmetry. Differences in developmental instability between the two metals were also detected, as well as differences between the two developmental instability measurements. For almost all measured traits, FA was greater on Cd- and Zn-contaminated compared to non-contaminated host plants. In contrast, CV_e of some traits was greater on non-contaminated host plants, yet for other traits CV_e was greater on contaminated host plants. There were also non-significant inverse relationships between FA and fitness of cabbage aphid populations. Due to weak correlations between FA and different patterns of two developmental instability measurements, this study does not support the hypothesis that developmental instability is a useful bioindicator of environmental quality.     

Purification and characterization of myrosinase from the cabbage aphid (Brevicoryne brassicae), a brassica herbivore.

Aphids are among the most serious insect pests of agricultural crops in the world. They often have specific hosts, and the cabbage aphid (Brevicoryne brassicae) is a specialist on Cruciferae. It has previously been described that certain insects contain the enzyme myrosinase (EC 3.2.3.1), which is considered an important defence enzyme of crucifers. Myrosinase was purified to homogeneity from cabbage aphid soluble extracts using anion-exchange and phenyl-Sepharose chromatography. The protein has an apparent subunit molecular mass of 57-58 kDa and is a dimer. The isoelectric point is 4.9 and the enzyme has a temperature optimum around 40 degrees C. The enzyme was active towards the glucosinolates tested, sinigrin and glucotropaeolin, but was inhibited by ascorbate at concentrations that normally activate plant myrosinases. Using sinigrin as the substrate Km was determined as 0.41 mM, and the kcat as 36 s(-1). With glucotropaeolin the Km and kcat values were determined as 0.52 mM and 22.8 s(-1), respectively. The enzyme was stable upon storage at 4 degrees C for many months, but lost some activity upon freezing. The insect myrosinase did not cross-react with antibodies raised to plant myrosinase. Peptide sequencing of a tryptic digest of the protein showed homology to beta-glucosidases. The presence of myrosinase in an insect pest specialist may be an example of a coevolution process that facilitates host specialization.     

Effect of various cauliflower cultivars on population density fluctuations of the cabbage aphid,Brevicoryne brassicae (L.) (Hom.: Aphididae) and its parasitoid Diaeretiella rapae (McIntosh) (Hymenoptera: Braconidae)

In this study, population density changes of the cabbage aphid, Brevicoryne brassica (L.), were tested in the field during 2011 under natural infestation at research field of the Shahed University (South of Tehran). This investigation was conducted on the eight cauliflower cultivars including Smilla, Snow mystique, White cloud, Buris, Galiblanka, Snow crown, SG and Tokita in randomised complete block design with five replications. Sampling was done after starting of aphid activity in the field every week and the total number of adult aphids and nymphs were counted in three leaves of the upper, middle and lower parts of the plant. In addition, the percentage of parasitism of the cabbage aphid by Diaeretiella rapae was evaluated. Results of the sampling showed that peak of the aphid population were at the first half of November. The parasitism percent of the cabbage aphid by D. rapae was significantly different among studied cultivars (p?<?0.05). Therefore, it can be concluded that using of Smilla, Buris and SG cultivars probably increases the efficiency of D. rapae in the control of the B. brassica (L.).     

Entomopathogenic potential of fungi isolated from intertidal environments against the cabbage aphid Brevicoryne brassicae (Hemiptera: aphididae)

The use of biopesticides formulated from entomopathogenic fungi is a strategy utilised in integrated pest management programmes. The microorganisms used in these biopesticides are isolated from terrestrial organisms and ecosystems. However, bioprospecting in marine environments may lead to the discovery of promising fungi for pest control. In this study, marine fungi were identified and evaluated for the control of Brevicoryne brassicae. The effects of the most virulent isolate so identified on the mortality of aphids were compared to the effects of bioinsecticides that were formulated from fungal strains of Beauveria bassiana (Bovemax®) and Metarhizium anisopliae (Methamax®). Moreover, lethal and sublethal effects of this isolate on B. brassicae biological parameters were also examined. The isolates were identified as Aspergillus versicolor, Aspergillus sydowii (isolates 1 and 2), Penicillium dipodomyicola, and Trichoderma harzianum. The fungal strain A. versicolor was the most virulent fungal species, causing 85.9% mortality in B. brassicae at 24 h. The mortality rate caused by A. versicolor was similar to that caused by Bovemax® and Methamax® at concentrations of 10⁵ conidia mL^?1, and superior to that caused by Methamax® at a concentration of 10⁹ conidia mL^?1. The exposure of B. brassicae to CL₂₅ (0.32 × 10³) of A. versicolor did not affect the net reproductive rate (R_o), average generation time (T), intrinsic rate of population growth (r_m), and finite rate of population increase (λ). This is the first study to demonstrate that A. versicolor isolated from a marine environment is a promising candidate for the biological control of agricultural pests.