The distribution of Myzus persicae (Sulz.) on year-round chrysanthemums

Large varietal differences in the susceptibility of chrysanthemums to Myzus persicae (Sulz.) were confirmed. The cultivar B.G.A. Tuneful supported forty times as many aphids as Portrait. In the winter, aphids bred more slowly and stabilized at a lower density than in the summer, but retained the same characteristic varietal distribution patterns. The unintentional introduction of the parasite Aphidius matricariae Hal. resulted in extermination of the aphid within 15 weeks. Mummies appeared in a series of distinct generations 17 days apart with a sevenfold increase between peaks. As this increase was at first not as rapid as that of the aphid, reduction of the pest population was not possible until the aphids had become self-limiting. Thus, although elimination was achieved, it was not economically satisfactory on susceptible varieties. The modifications needed to employ A. matricariae for commercial biological control under glass are discussed.     

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.     

Electrophoretic study of genetic variation in British Myzus persicae (Sulz.) (hemiptera,aphididae)

Thirty-five clones of the green peach aphid, Myzus persicae Sulz., representing a wide range of host plants and geographical origins, were examined electrophoretically. Only 11 of 26 enzymes were active enough for subsequent work. Since genetic crosses are very difficult to make in the parthenogenetic M. persicae, assigning bands to loci and alleles is necessarily arbitrary. Thirty-two isozyme bands were detected. Only two of these (Est-1 and Est-3) migrated to different distances in some clones. This is a very low level of interclone variation, considering the known properties and origins of the clones. The peculiar feeding habits of aphids may perhaps partly explain the inactivity of so many enzymes in M. persicae (which are active in other insects). The scarcity of interclone variation in isozyme migration distance in M. persicae clones may be the result of its fast parthenogenetic reproduction and high migration ability of alates, combined with the effects of natural and artificial selection (e.g., by insecticides). Surviving genotypes may be rather few, each represented by numerous individuals. The only type of widespread electrophoretic variation is in the intensity of two esterase bands (Est-1 and Est-2). Five hypotheses are presented to explain this variation and discussed in view of evidence from other organisms.     

Feeding and the uptake of phosphamidon by two strains of Myzus persicae (Sulz.) on radish plants

Intraspecific differences in the uptake of solutions containing phosphamidon, enclosed in Parafilm membranes, have previously been demonstrated in Myzus persicue. This paper shows that similar differences also occur when the aphids are fed on treated plants. Uptake from phosphamidon-contaminated plants is reduced though the effect was quantitatively different in the two strains of aphid studied. The depression in the level of feeding was related to the concentration of insecticide applied to the plant.     

Evidence for trichromacy in the green peach aphid, Myzus persicae (Sulz.) (Hemiptera: Aphididae)

The green peach aphid, Myzus persicae (Hemiptera: Aphididae) is an important phytophagous pest of greenhouse and field crops. In the host finding process visual cues are of paramount importance. In order to contribute to the understanding of the perception of visual stimuli in this species, we measured the electroretinogram of alate female summer migrants of M. persicae. The spectral sensitivity was measured in 10nm steps under both dark and light adaptation from 320 to 640 nm. The dark adapted spectral sensitivity curve showed one maximum in the green region around 530 nm and a distinct shoulder between 500 and 510 nm. In presence of adapting light, a secondary blue-green peak (490 nm) and a third peak in the near UV (330-340 nm) were observed. From these results we conclude that M. persicae has three spectral types of photoreceptors.     

Effects on Myzus persicae (Sulz.) and transmission of beet yellows virus of applying certain trace elements to sugar beet

Applications of lithium chloride (LiCl), zinc sulphate (ZnSO₄) or nickel sulphate (NiSO₄) to the roots of sugar-beet plants in the glasshouse encouraged settling on the leaves of adult apterae from a clone of Myzus persicae (Sulz.); conversely, treatment with boric acid (H₂B₂O₇) inhibited aphid settling. Larviposition of M. persicae was increased by NiSO₄ and tin chloride (SnCl₂). Viruliferous M. persicae transmitted beet yellows virus (BYV) more efficiently to plants treated with LiCl or H₂B₂O₇ than to those treated with copper sulphate (CuSO₄), ZnSO₄ or SnCl₂. The sulphate and chloride anions of the applied chemicals appeared to have little effect on M. persicae and virus transmission. It is suggested that applications of trace elements to sugar beet affected M. persicae and virus transmission by changing the concentrations of trace elements in the aphids' diet and by altering the metabolism of the leaf tissues in the host plant.     

Comparison of the biology of Myzus persicae Sulz. resistant and susceptible to dimethoate

Apterous Myzus persicae resistant to dimethoate reproduce for the same length of time as susceptible aphids, but the resistant ones reproduce significantly faster during the first 10 days of adult life (especially during the first 5 days). Thereafter, they reproduce more slowly, and eventually the susceptible aphids produce approximately the same number of larvae. Resistant aphids die significantly younger. Resistant aphids as larvae develop faster than susceptible ones and are significantly heavier when they first become adult. The resistant aphids do not excrete faster during the first few days but, as they produce more larvae during the first 10 days of adult life and have developed faster, they probably feed faster during development and early adult life or obtain more nutritious food. Resistant aphids were at least as effective as susceptible ones in transmitting sugar-beet mosaic and pea mosaic viruses, and plants showed symptoms sooner when resistant aphids were the vectors.     

Effects of Pepper (Capsicum annuum) Cultivars on the Biology and Life Table Parameters of Myzus persicae (Sulz.) (Hemiptera: Aphididae)

Green peach aphids, Myzus persicae (Sulz.) (Hemiptera: Aphididae), obtained from pepper fields, were colonized on susceptible pepper plants in a growth chamber. The development, survivorship, and life table parameters of the green peach aphid were evaluated on nine peppers cultivars as follows: Almuden, Bilano, Bird, Cabezo, de la Sierra, Eppo, Jaen, Raza, and Yatasto at controlled conditions (20?±?1°C; about 70% RH; 14h photophase). The development times of immatures ranged from 6.1 days on Yatasto to 11.4 days on Jaen, whereas immature survival was close to 100% on all cultivars. The intrinsic rate of increase (r _m ) for green peach aphid on Bilano and Yatasto were the highest. Jackknife estimates of r _m varied from 0.281 to 0.174 females/female/day on Yatasto and Jaen, respectively. The mean population generation times (T) on these hosts ranged from 13.7 to 22.7 days. The highest net reproductive rates (R ₀ ) were on Bird and Bilano (63.8 and 62.89 females/female/generation, respectively) and the lowest on De la Sierra and Almuden (34.1 and 38.7, respectively). Because of the high coefficient of determination (R ²) values in Gompertz and Weibul models, survival data from different cultivars had a good fit to both models. The results pointed Jaen, Almuden, and Raza cultivars as the least suitable host plants, indicating that they were the most resistant to M. persicae among the cultivars we tested.     

Quantitative and qualitative variation in the mRNA for carboxylesterases in insecticide-susceptible and resistant Myzus persicae (Sulz)

RNA was extracted from two insecticide-resistant clones and one susceptible clone of M. persicae. The resistant clones each produced large amounts of one of two closely related carboxylesterases, the enzymes responsible for cross-resistance to a wide range of insecticides. After purification by affinity chromatography on oligo(dT) cellulose, the mRNA was translated into protein in a rabbit reticulocyte lysate system with [l-³⁵S]methionine. The resultant radiolabelled esterases were immunoprecipitated from the products with IgG prepared from an antiserum to one form of the enzyme, but cross-reacting with both. The bound enzyme was extracted by affinity chromatography on protein A sepharose, and characterized alongside the total radiolabelled proteins by SDS electrophoresis and fluorography. The translation products of the two resistant clones each contained large amounts of an immunoprecipitable protein. However, no such protein was detected in the translation products of the mRNA from susceptible aphids showing that resistant aphids produce much more of the mRNA encoding the enzymes responsible for resistance. It was also shown that the enzymes from the two resistant clones had primary structures differing from each other by 1 kDa. In addition, the nascent forms of both enzymes differed from their native forms by 8 kDa and glycosylation was shown to be responsible for this post-translational modification. The likely genetic basis of the changes in mRNA is discussed and related to the karyotype of the resistant clones.     

Some effects of spraying with thiabendazole on the susceptibility of sugar beet to yellowing viruses and on their vector, Myzus persicae (Sulz.)

In a field experiment fewer sugar-beet plants became infected with aphid-transmitted yellowing viruses in plots that had been sprayed with solutions of thiabendazole lactate than in water-sprayed plots, after exposure to natural infestation with aphids. Subsequent glasshouse tests showed that foliar sprays of o·o1 % thiabendazole lactate in water significantly reduced the proportion of inoculated sugar-beet plants which became infected with beet yellows virus (BYV) or beet mild yellowing virus (BMYV) after inoculation with viruliferous Myzus persicae (Sulz.). This effect on virus transmission was not apparently due to a direct insecticidal action of thiabendazole, because adult aphids usually survived equally well on sprayed and unsprayed plants. Treatment of test plants with thiabendazole did not affect the transmission of beet mosaic virus to them by M. persicae. The fecundity of M. persicae was greatly reduced by transferring them to plants which had been sprayed with thiabendazole or by spraying them with thiabendazole before transfer to unsprayed plants. The fertility of adult Aphis fabae Scop, was also reduced by spraying with thiabendazole. The mechanisms whereby thiabendazole affected fecundity of aphids and transmission of viruses are not understood.