Trichomes of Lycopersicon spp. and their effect on Myzus persicae (Sulzer) (Hemiptera: Aphididae)

Abstract The green peach aphid ( Myzus persicae ) is becoming resistant to many of the pesticides used in the tomato ( Lycopersicon esculentum ) industry. A potential alternative method of control is host-plant resistance, which may be mediated by trichomes. Resistance to the green peach aphid was assessed for six accessions of L. hirsutum, three of L. pennellii and a L. esculentum control. Mortality, entrapment and number of aphids unaffected by trichomes were recorded 24, 48 and 72 h after placement. Using multiple regression against counts of glandular and non-glandular trichomes, the role of foliar pubescence in resistance to the aphid was established. Lycopersicon pennellii possessed the highest level of resistance after 72 h and type IV trichome density accounted for 26.5% of variance in mortality ( P  < 0.001). Low densities of type IV and high densities of type VII trichomes increased the number of aphids 'unaffected' by trichomes, a relationship accounting for 29% of variance ( P  < 0.001). Information on which types of trichomes most strongly affect resistance to insect pests will aid future breeding and L. pennellii shows potential for use in breeding programs to increase levels of host-plant resistance in L. esculentum.     

Green peach aphid [Myzus persicae (Sulzer) (Hemiptera: Aphididae)] control using Brassicaceae ethyl ester oil sprays

Control of green peach aphid (Myzus persicae), a globally important pest, using plant‐derived oils is a promising alternative to conventional insecticides. Although various plant‐derived oils are potentially useful for insect control, dose–response studies and efficacy comparisons among oils have not been widely reported. Our objective was to compare M. persicae control by plant‐derived oils, focusing on oils derived from Brassicaceae species that exhibit rotational and environmental quality benefits. We thus applied sprays of emulsified ethyl esters from the seed oils of yellow mustard (Sinapis alba), oriental mustard (Brassica juncea) and rapeseed (Brassica napus) to M. persicae in a laboratory bioassay. A dose–response relationship was modelled for the S. alba spray yielding LD₅₀/LD₉₅ values of 18.2 ± 0.87/128.1 ± 5.10 μg ester per cm² (P < 0.0001). Ethyl esters of oils from all three species and soybean (Glycine max) ethyl ester were compared to determine the efficacy of Brassicaceae oils relative to the dominant plant‐oil spray currently available. All ethyl esters were equally efficacious despite measured differences in fatty acid profiles among the oils. Oils derived from mustards B. juncea and S. alba are potentially useful feedstocks for the production of insecticidal sprays, and testing on additional insects is warranted.     

Population parameters and growth of Myzus persicae Sulzer (Hemiptera: Aphididae) under elevated CO2 concentrations in the air

The effects of three different CO₂ concentrations (400, 600, and 1000 ppm) on the population parameters and growth of the green peach aphid, Myzus persicae, were examined. Raw life history data from M. persicae were analyzed using an age-stage, two-sex life table to take into account the viable development rate among individuals. The population projections of M. persicae indicate the stage structure and variability of the population growth under different CO₂ concentrations based on an age-stage, two-sex life table analysis. Significantly longer oviposition duration and higher fecundity were observed under elevated CO₂ (600 and 1000 ppm) than those under ambient CO₂ (400 ppm). Furthermore, the M. persicae population reared under elevated CO₂ concentrations showed higher intrinsic and finite rates of population increase than under ambient CO₂ concentrations. These results indicate that the population parameters and growth of M. persicae were positively influenced in the fecundity by elevated CO₂ concentrations relative to the ambient CO₂. These findings indicate that it is basically remained to understand the direct effects of CO₂ elevation on the host plants, and the interaction between the host plants and M. persicae in the same CO₂ concentration for establishing more realistic population growth model systems for M. persicae in the aerial environment rising CO₂ concentration level.     

Pathogenicity of hyphomycet fungi to aphids Aphis gossypii Glover and Myzus persicae (Sulzer) (Hemiptera: Aphididae)

The aphids Aphis gossypii and Myzus persicae are cosmopolitan, poliphagous and damage cultivated plants. The effects of the entomopathogenic fungi Beauveria bassiana (isolate IBCB 66), Metarhizium anisopliae (isolate IBCB 121), Paecilomyces fumosoroseus (isolate IBCB 141) and Lecanicillium (= Verticillium) lecanii (isolate JAB 02) on third instar nymphs of A. gossypii and M. persicae were evaluated in the laboratory at 25 degrees C, 70 +/- 10% RH and 12h photophase. The aphids were transferred to petri dishes with a foliar disk (cotton or pepper) with a layer of 1 cm tick of agar-water. The fungi were applied in a suspension containing 1.0 x 106 to 1.0 x 108 conidia/ml. In the control treatment 1 ml of sterilized water was added to the foliar disks. The mortality of aphids was evaluated daily. B. bassiana and M. anisopliae caused 100% mortality at the seventh day after inoculation, for both species. L. lecanii was the fungus that provided mortality later in the aphids and M. persicae was more susceptible to both fungi than A. gossypii.     

Segregation of autosomes during spermatogenesis in the peach-potato aphid (Myzus persicae) (Sulzer) (Hemiptera: Aphididae)

Most aphids are cyclic parthenogens, so are ideal models in studies of the mechanisms and consequences of sex and recombination. However, owing to a shortage of physical and genetic markers, there have been few studies of the most fundamental genetic processes in these organisms. For example, it is not known whether autosomal segregation during male spermatogenesis is in Mendelian proportions: we address that question here. The aphid Myzus persicae has a typical karyotype of 2n = 12 in females (XX), while males are XO (2n = 11). During male meiosis, only the spermatocytes with an X chromosome are viable. We hypothesized that assortment of autosomes might be non-random because chromosomal imprinting leading to elimination of the paternal autosomes is seen in the closely related coccoids. In other aphid models, we have observed segregation distortions at single microsatellite loci (Wilson, 2000). Such distortions may have nothing to do with 'selfish' behaviour, but may be caused by mutation accumulation causing fitness differentials. Thus single-locus distortions might be predicted to be more likely to be detected via the male lines of clones that have lost the ability to reproduce sexually (male-producing obligate parthenogenesis (androcyclic)). Using microsatellites we show that genetic imprinting or selfish autosome behaviour does not occur in male M. persicae. Generally, loci segregated in Mendelian proportions in both sexes of cyclically parthenogenetic (holocyclic) clones. However, in androcyclic clones, segregation distortions consistently involved the same two autosomes. This is consistent with linkage of markers to deleterious mutations associated with a loss of sexual reproduction.     

Use of silicon as inductor of the resistance in potato to Myzus persicae (Sulzer) (Hemiptera: Aphididae)

The aphid Myzus persicae (Sulzer) is an important pest of potato and causes direct harm, due to the quantity of sap extracted and for being vector of important phytovirus. This work was carried out to evaluate the action of silicon as a resistance inducer of potato to M. persicae. Four treatments were tried: foliar fertilization with silicon acid at 1%; soil fertilization with 250 ml silicic acid solution at 1%; foliar fertilization with silicon acid at 1% + soil fertilization with 250 ml silicic acid solution at 1%; and a control. The treatments were applied thirty days after the explants emergence. Fifteen days after the application of the treatments, feeding preference and some biological aspects of the aphids were evaluated. After, the content of tannins and lignin present in the leaves and the activity of the enzymes peroxidase and phenylalanine ammonia-lyase were also determined. The silicon fertilization did not affect the preference of the aphids; however it reduced fecundity and the rate of population growth of the insects. The lignin percentage increased in the leaves of plants fertilized with silicon via soil and/or foliar and the percentage of tannins increased only in the leaves fertilized via soil plus foliar. The silicon acted as a resistance inducer to M. persicae in potato.     

Efficacy of the parasitoid,Diaeretiella rapae (McIntosh) (Hymenoptera: Braconidae) against Myzus persicae (Sulzer) (Hemiptera: Aphididae) infesting rapeseed-mustard

Efficacy of Diaeretiella rapae (McIntosh) (Hymenoptera: Braconidae) was determined by studying its biological and behavioural attributes on the aphid, Myzus persicae (Sulzer) (Hemiptera: Aphididae). Total developmental duration of the parasitoid was longer in younger instars compared to that in older instars of aphid. Host age negatively affected the oviposition period and fecundity of the ovipositing parasitoid. Survival of the immatures was higher in older than the younger instars of the aphid. Sex ratio for the parasitoid was female-biased. Longevity of female parasitoid was higher while parasitizing aphid nymphs of younger age groups (1–2 days old) compared to that of older age groups (4–5 days old). Parasitoid showed a higher preference towards second instar of M. persicae both in choice and no-choice tests. Results on mutual interference revealed that per capita searching efficiency decreased from 0.91 to 0.07 as parasitoid densities increased from 1 to 8. Logistic regression exhibited a type II functional response for D. rapae. The estimated values of search-efficiency (a) and handling time (T_h) were 0.038 h⁻¹ and 1.59 h, respectively. The maximum parasitization rate was 15.08. This investigation suggests that D. rapae could be an effective candidate for augmentative biological control of M. persicae which infests several plant species of economic importance.     

Continuous occurrence of intra-individual chromosome rearrangements in the peach potato aphid, Myzus persicae (Sulzer) (Hemiptera: Aphididae)

Analysis of the holocentric mitotic chromosomes of the peach-potato aphid, Myzus persicae (Sulzer), from clones labelled 50, 51 and 70 revealed different chromosome numbers, ranging from 12 to 14, even within each embryo, in contrast to the standard karyotype of this species (2n?=?12). Chromosome length measurements, combined with fluorescent in situ hybridization experiments, showed that the observed chromosomal mosaicisms are due to recurrent fragmentations of chromosomes X, 1 and 3. Contrary to what has generally been reported in the literature, X chromosomes were frequently involved in recurrent fragmentations, in particular at their telomeric ends opposite to the nucleolar organizer region. Supernumerary B chromosomes have been also observed in clones 50 and 51. The three aphid clones showed recurrent fissions of the same chromosomes in the same regions, thereby suggesting that the M. persicae genome has fragile sites that are at the basis of the observed changes in chromosome number. Experiments to induce males also revealed that M. persicae clones 50, 51 and 70 are obligately parthenogenetic, arguing that the reproduction by apomictic parthenogenesis favoured the stabilization and inheritance of the observed chromosomal fragments.     

Cage and field assessments of Beauveria bassiana-based Mycoinsecticides for Myzus persicae Sulzer (Hemiptera: Aphididae) control in cabbage

The efficiency of formulated Beauveria bassiana-based mycoinsecticides to control Myzus persicae (Sulzer) in cabbage was assessed under field conditions. Aqueous conidial suspensions (0.01% Tween 80 + 0.01% v/v Agral) of three fungal isolates were sprayed twice at different dates, each with 2.0 x 10(9) viable conidia per potted plant using screened cages. The number of nymphs and adults of M. persicae per leaf was significantly reduced in plots treated with isolates CG 864 and PL 63, with control efficiency ranging from 57% to 60%. Further field trials using screened cages with isolate CG 864 formulated as oil dispersion reduced the aphid population by 85-87% as compared to the control, whereas a 71% reduction was seen in plants treated with the aqueous conidial suspension 20 days following the first spray. The last experiment was conducted in a commercial cabbage field (without cages), in which the fungus was applied at three different dates, each with an equivalent of 1.0 x 10(13) viable conidia/ha. The reduction in the number of aphids per leaf was more evident between four and five weeks following the first spray, resulting in 76-83% and 57-65% control efficiency for oil dispersions and unformulated conidia, respectively. However, with the exception of imidacloprid-treated plants, rapid aphid re-infestation was observed in all treatments. In this study, the stand-alone use of mycoinsecticides for aphid control was not a satisfactory strategy, although utilization of B. bassiana in IPM strategies remains a field to be explored.     

Life cycle variation of Myzus persicae (Hemiptera: Aphididae) in Greece

During the years 1995-1999 the life cycle category of 2797 clones of Myzus persicae (Sulzer) was examined. The clones originated from primary and secondary hosts from different localities of North and Central Greece and the island of Crete in the south. Four different overwintering life cycle strategies were found that have also been described for M. persicae and other heteroecious species previously. A geographical variation was found in the proportion of holocyclic clones from tobacco and other secondary hosts associated with the abundance of the primary host in the sampling regions. In Central Macedonia, around the main peach-growing regions, the proportion of holocyclic clones was mostly above 50% and in some cases reached 100%. In localities of East Macedonia, holocyclic clones were also frequent. On the other hand, further south or in north-eastern Greece, where peach is not common, the proportion of holocyclic clones varied between 0 and 33%. Fifty seven percent of examined anholocyclic clones produced males under short day conditions, suggesting that androcyclic clones in Greece represent an important factor of genetic variability. Intermediate clones were sampled from all host-plants but at low frequencies (3.6% of total examined clones and 6.9% of non-holocyclic ones). Moreover, a regional variation was found in different colour forms feeding on tobacco plants. Red clones were predominant in regions where aphids overwinter parthenogenetically on weeds or winter crops. However, almost all clones from the primary host were green. The ecological aspects of life cycle variation are discussed.     

Studies on the morphometry of the green peach aphid, Myzus persicae (Sulzer) (Homoptera: Aphididae)

Aphids are one of the most important groups of phytophagous insects because of their polyphenism, host alternation, heteroecious behavior and reproductive habits. Laboratory culture of the aphid Myzus persicae on the host plant Brassica pekinensis Hubner was maintained seasonally for biometrical studies. The metric analysis revealed gradual developmental changes from the first instar nymph to the adult stage in size, shape, and a number of characters. The transitional changes were sufficiently distinct to allow differentiation of each of the life stages irrespective of the season. A key to the nymphal stages of the pest is provided.     

噻虫胺对桃蚜的毒力及其亚致死剂量对桃蚜解毒酶系活力的影响

为明确噻虫胺对桃蚜Myzus persicae (Sulzer)的毒力和桃蚜的代谢解毒机制, 本研究采用点滴法、 叶片浸渍法和叶柄内吸法分别测定了噻虫胺对桃蚜的毒力, 以及胡椒基丁醚（PBO）、 磷酸三苯酯（TPP）和顺丁烯二酸二乙酯（DEM）对噻虫胺毒力的影响; 检测了噻虫胺在亚致死剂量LC₆, LC₁₅和LC₃₀下对桃蚜体内乙酰胆碱酯酶、 羧酸酯酶和谷胱甘肽-S-转移酶活力的影响。结果表明: 噻虫胺对桃蚜点滴、 浸渍和内吸LC₅₀分别为1.891, 2.341和1.303 mg/L; 3种酶抑制剂分别与噻虫胺按1∶1混用, PBO对噻虫胺增效达2.41倍, 增效作用显著; TPP对噻虫胺增效达1.52倍, 增效作用也较明显; DEM对噻虫胺无增效作用。以噻虫胺LC₃₀浓度处理桃蚜, 处理后24 h其体内乙酰胆碱酯酶比活力受到显著抑制, 抑制率达41.2%; 以LC₁₅和LC₃₀浓度的噻虫胺处理桃蚜, 处理后24 h其体内羧酸酯酶比活力分别是对照的1.29和1.36倍, 有显著诱导激活作用; 以噻虫胺LC6, LC₁₅和LC₃₀浓度处理的桃蚜, 对其体内谷胱甘肽-S-转移酶的抑制率分别达7.9%, 11.9%和22.7%。结果说明噻虫胺对桃蚜具有较高毒力, 羧酸酯酶和多功能氧化酶可能是桃蚜体内代谢噻虫胺的主要酶系。     

Host-correlated morphological variation of Myzus persicae (Hemiptera: Aphididae) populations in Greece

Morphological variation in nine characters of 157 clones of Myzus persicae (Sulzer) was examined by multivariate analysis. The clones were collected from peach, Prunus persica, the primary host and the secondary hosts tobacco, Nicotiana tabacum, cabbage, Brassica oleracea, sugarbeet, Beta vulgaris and pepper Capsicum annuum. The 156 clones originated from various regions of Greece, both in the north, where a large part of the population has an annual bisexual generation on peach, and in more southerly regions, where populations are predominantly unisexual. One clone was collected from tobacco in Caserta, Italy. All clones were laboratory-reared on potato. Canonical variate analysis, hierarchical cluster analysis and a non-parametric classification tree method both revealed morphological differences associated with the host-plant on which they were collected. The scores of the first two canonical variates separated the tobacco-feeding clones from those originating from other secondary host-plants. However, in tobacco-growing areas the tobacco-feeding form predominated in spring populations on peach, and was sometimes found on other secondary hosts. In addition, using cluster analysis, the clones from tobacco which were sampled in the most southeasterly region showed a relatively large phenotypic distance from those collected further north and west. Moreover, clonal phenotypes were affected both by host plant and by long-term parthenogenetic rearing. However, in spite of these effects, the tobacco form was generally distinguishable from aphids originating from other hosts, indicating that the difference must have a genetic basis. In separate analyses of the clones originating from secondary hosts no association was found between morphology and either life cycle category or colour. Discriminant analysis showed that 89% of 1723 specimens could be correctly classified into the two groups.     

Antibiosis and antixenosis of six commonly produced potato cultivars to the green peach aphid, Myzus persicae Sulzer (Hemiptera: Aphididae)

The antibiotic and antixenotic resistance of six commonly produced potato cultivars in Iran including Aozonia, Agria, Cosima, Cosmos, Kondor and Savalan to the green peach aphid, Myzus persicae Sulzer, were investigated under laboratory conditions at 20 ± 2oC, 65 ± 5% RH and 16:8h (L:D) in 2009. Antibiosis experiments showed significant differences in the developmental time, nymphal survivorship, fecundity, adult longevity of the green peach aphid among the potato cultivars. Intrinsic rate of natural increase (r m) for apterous aphids varied significantly with the potato cultivars on which the aphids were reared. This value ranged from 0.225 to 0.293 females/female/day, which was lowest on Cosmos and highest on Aozonia. Additionally, the estimated net reproductive rate (R0) and finite rate of increase (λ) for apterous aphids were the lowest on Cosmos. For the antixenosis experiment, no significant difference was found in aphid's preference to the potato cultivars. However, Aozonia was preferred more than the other five cultivars by the apterous aphids. Therefore, our results demonstrated that among the investigated cultivars the Cosmos cultivar is moderately resistant to the green peach aphid.     

Resistance of potato cultivars to Myzus persicae (Sulz.) (Hemiptera: Aphididae)

Aphids are the most important vectors of viruses infecting potato (Solanum tuberosum). We focused on the response of the aphid vector Myzus persicae (Sulzer) to five commercial potatocultivars: ágata, Jaette Bintje, Mondial, Monalisa and Santè, by traditional antibiosis and antixenosis tests and by the EPG (Electrical Penetration Graph) technique, as a step forward to the design of effective management practices. Our aim was to identify plant factors involved in resistance of these cultivars against M. persicae, both at the surface and in deeper plant tissues. Results from the antixenosis test confirmed a strong preference of M. persicae for the Mondial cultivar. The antibiosis study indicated a lower population development of the aphid in 'Monalisa' when compared to 'ágata' and 'Jaette Bintje'. EPG assays indicated that 'Santè' inhibited the initial feeding process of M. persicae, whereas 'Monalisa' showed a physical-type of resistance as demonstrated by a very high number of short probes. The cultivar Mondial showed average values for all EPG variables analyzed. The behavior in 'Jaette Bintje' indicated this cultivar was an ideal host for aphid feeding and reproduction. Together, the EPG data revealed the existence of pre and post-phloematics factors in the cultivars under study, which have important implications on the efficiency of transmission and spread of virus in potato by M. persicae.     

Effects of kaolin particle film on Myzus persicae (Hemiptera: Aphididae) behaviour and performance

The emergence of resistance mechanisms to, and revocation of, many insecticides used in the control of the polyphagus aphid pest, Myzus persicae (Sulzer), has increased the pressure to develop novel approaches for the control of the pest in many crops. Kaolin-based particle films provide a physical barrier against insect pests and show considerable potential for controlling M. persicae. We conducted a series of laboratory experiments to investigate the mode of action of kaolin against aphids. The material appeared to have no direct effect on M. persicae; spraying adult aphids with aqueous kaolin suspension had no significant impact on their subsequent survival or reproduction on untreated plants. Similarly, when aphids were placed on kaolin-treated host-plants (Brassica oleracea), their performance (survival, growth rate and reproduction) was not significantly different from aphids on untreated plants. However, when M. persicae were given a choice between kaolin-treated and untreated (or water solvent-treated) leaf areas, both adults and nymphs exhibited a significant preference for non-kaolin-treated host-plant material. Rejection of kaolin-treated plant material occurred very rapidly (within 20 min) and this behavioural effect may be related to the efficacy of kaolin in controlling aphids under field conditions.     

Plant Essential Oils Synergize and Antagonize Toxicity of Different Conventional Insecticides against Myzus persicae (Hemiptera: Aphididae)

Plant-derived products can play an important role in pest management programs. Essential oils from Lavandula angustifolia (lavender) and Thymus vulgaris (thyme) and their main constituents, linalool and thymol, respectively, were evaluated for insecticidal activity and synergistic action in combination with insecticides against green peach aphid, Myzus persicae (Sulzer) (Hemiptera: Aphididae). The essential oils and their main constituents exerted similar insecticidal activity when aphids were exposed by direct sprays, but were non-toxic by exposure to treated leaf discs. In synergism experiments, the toxicity of imidacloprid was synergized 16- to 20-fold by L. angustifolia and T. vulgaris essential oils, but far less synergism occurred with linalool and thymol, indicating that secondary constituents of the oils were probably responsible for the observed synergism. In contrast to results with imidacloprid, the insecticidal activity of spirotetramat was antagonized by L. angustifolia and T. vulgaris essential oils, and linalool and thymol. Our results demonstrate the potential of plant essential oils as synergists of insecticides, but show that antagonistic action against certain insecticides may occur.     

Microsatellite isolation, linkage group identification and determination of recombination frequency in the peach-potato aphid, Myzus persicae (Sulzer) (Hemiptera: Aphididae)

Fifteen polymorphic microsatellite markers were used to establish linkage groups and relative rates of recombination in male and female Myzus persicae (Sulzer) (Hemiptera: Aphididae) (peach-potato aphid). We cloned nine markers from M. persicae and for these we report primer sequences and levels of allelic diversity and heterozygosity in four Australian M. persicae populations. Of the remaining six loci, four loci, also cloned from M. persicae, were obtained from G. Malarky (Natural History Museum, London) and two loci from Sitobion miscanthi were used. Additionally, the primer sequences of locus M77, a locus monomorphic in M. persicae but polymorphic in the closely related Myzus antirrhinii, are presented. Eleven of the 15 polymorphic markers were autosomal and four were X-linked. A linkage analysis was performed on a European pedigree of aphids containing five families with between seven and 11 offspring each. There was no linkage between any loci in females. In males, several pairwise comparisons yielded no recombinant offspring. With the exception of locus M40, these observations were supported in a linkage analysis performed on larger families produced from Australian M. persicae crosses. Locus M40 showed segregation consistent with involvement in a translocation between autosomes 1 and 3 in European samples but not in the Australian samples. From the Australian crosses we report an absence of recombination in males but high recombination rates in females. One X chromosome and four autosomal linkage groups were identified and tentatively assigned to chromosomes. The relevance of achiasmate meiosis to the evolution of sex is discussed.     

Performance of Myzus persicae (Hemiptera: Aphididae) clones on different host-plants and their host preference

The performance of eighteen clones of Myzus persicae (Sulzer) on pepper and tobacco plants at 20 degrees C and L16:D8 and the choice of young adult apterae between tobacco and pepper leaf-discs were examined. The clones were collected from weeds and peach in two tobacco-growing regions: Katerini, northern Greece and Karditsa, central Greece (only from weeds) and from Lehonia, central eastern Greece where tobacco is not cultivated. All clones did well on both hosts. However, the analysis of data revealed a significant effect of "region / host plant origin" on aphid performance. The mean values of adult weight, intrinsic rate of increase and fecundity of the clones collected in Lehonia and reared on tobacco were significantly lower than the observed values for clones from Katerini and Karditsa. Aphids from Lehonia had significantly higher mean values for developmental time on tobacco than clones from the other regions whereas the opposite was observed when aphids were reared on pepper. Aphids collected in Lehonia performed better on pepper than those originating from the tobacco-growing regions. A choice test revealed differences among the clones originating from different regions. Fifty three percent and 43% of aphids from weeds and peach from Lehonia, respectively, chose pepper. By comparison 41.5% and 40.0% of aphids from peach and weeds from Katerini, respectively and 49.5% of aphids from Karditsa preferred tobacco. The results are discussed in relation to host specialization in M. persicae.