Distribution of common genotypes of Myzus persicae (Hemiptera: Aphididae) in Greece, in relation to life cycle and host plant

Microsatellite genotyping was used to identify common clones in populations of the Myzus persicae group from various hosts and regions in mainland Greece and southern Italy and to compare their distribution and occurrence on tobacco and other crops. Common clones were defined as genotypes collected at more than one time or in more than one population; and, therefore, unlikely to be participating in the annual sexual phase on peach. Sixteen common genotypes were found, accounting for 49.0% of the 482 clonal lineages examined. Eight of these genotypes were subjected, in the laboratory, to short days and found to continue parthenogenetic reproduction, i.e. they were anholocyclic. Four of the six commonest genotypes were red, and one of these accounted for 29.6% of the samples from tobacco and 29.4% of those from overwintering populations on weeds. All six commonest genotypes were found on weeds and five of them both on tobacco and on other field crops. In mainland Greece, the distribution of common clones corresponded closely with that of anholocyclic lineages reported in a previous study of life cycle variation. Common genotypes were in the minority in the commercial peach-growing areas in the north, except on weeds in winter and in tobacco seedbeds in early spring, but predominated further south, away from peach trees. This contrasts with the situation in southern Italy, reported in a previous paper, where peaches were available for the sexual phase, yet all samples from tobacco were of common genotypes. © 2007 Cambridge University Press

Long-term studies on the evolution of resistance of Myzus persicae (Hemiptera: Aphididae) to insecticides in Greece

The aphid Myzus persicae s.l. (Hemiptera: Aphididae) is an important pest of many crops worldwide with a complex life cycle, intensely controlled by chemical pesticides, and has developed resistance to almost all used insecticides. In Greece, the aphid exhibits high genetic variation and adaptability and it is a classic example of evolution in the making. We have been studying M. persicae for over 20 years, on different host plants and varying geographical areas, analyzing its bio-ecology and the ability to develop resistance to insecticides. In this review, we present new and historical data on the effectiveness of insecticides from seven chemical groups used to control the aphid in Greece and the incidence of seven resistance mechanisms, including the new fast-spreading R81T point mutation of the postsynaptic nicotinic acetylcholine receptor. Thousands of samples were tested by biological, biochemical and molecular assays. The aphid populations were found to have developed and maintain resistance at medium to high levels to organophosphates, carbamates, pyrethroids and neonicotinoids for decades. In the latter group, a marked increase is recorded during an ~10-year period. The data analyzed and the extensive bibliography, advocate the difficulty to control the aphid making the design and application of IPM/IRM programs a challenge. We discuss principles and recommendations for the management of resistance, including the use of compounds such as flonicamid, spirotetramat, flupyradifurone and sulfoxaflor. We emphasize that resistance is a dynamic phenomenon, changing in time and space, requiring, therefore, continuous monitoring. © 2020 The Author(s). Published by Cambridge University Press

Evolution of imidacloprid resistance in Myzus persicae in Greece and susceptibility data for spirotetramat

BACKGROUND: Myzus persicae s.l. is a major crop pest globally and has evolved resistance to a range of insecticide classes making it increasingly difficult to control in some areas. Here we compare bioassay monitoring data for two important compounds, imidacloprid and spirotetramat, on field samples/clones collected in Greece. RESULTS: A total of 122 aphid samples/clones from central and northern Greece were examined in dose–response bioassays with imidacloprid. There was an overall increase in the level of resistance (resistance factor = 15–40) within tobacco-collected samples from 78.7% in 2007 to 86.7% in 2015. The corresponding frequencies for peach samples were 13.3% and 6.7%. These results were confounded however by the first identification of the R81T target mutation in Greece during 2015 (4.3% as heterozygotes in peach) and 2016 (21.3% as heterozygotes in peach). No resistance to spirotetramat was found at the 60 clones collected in 2015. CONCLUSION: Resistance to imidacloprid is continuing to increase within Greek M. persicae s.l. populations and the situation is likely to deteriorate further with the recent identification of the R81T resistance mutation. Resistance to spirotetramat has not been found and is therefore a good alternative to neonicotinoids for resistance management. © 2017 Society of Chemical Industry. © 2017 Society of Chemical Industr

Effect of synthetic insecticides on the larvae of Coccinella septempunctata from Greek populations

Coccinella septempunctata L. is one of the most abundant ladybird species in Greece, preying on several aphid species and other arthropods, of which many are pests of cultivated plants. These pests are usually controlled with chemical insecticides. During this process, however, beneficials are also exposed to pesticides. The development of Integrated Pest Management (IPM) programs against aphids requires the evaluation of the effects of insecticides on beneficial insects. We evaluated the LD50 of imidacloprid, acetamiprid, bifenthrin and deltamethrin on first, second, third and fourth instar larvae of C. septempunctata by topical application. Moreover, we studied their sublethal effects (LD10) on the development, weight and prey consumption of fourth instar larvae. The topical application bioassays showed that deltamethrin and bifenthrin were highly toxic to all larval instars, whereas imidacloprid and acetamiprid were less toxic to fourth instar larvae. The LD10 dose significantly affected, developmental time, adult weight and daily predation. These results show the importance of assessing potential effect of insecticides on C. septempunctata for developing effective IPM programs of aphids in Greece. © 2017, Springer Science+Business Media Dordrecht

Co-existence of different host-adapted forms of the Myzus persicae group (Hemiptera : Aphididae) in southern Italy

Multivariate morphometric analysis (method of canonical variates) was used to compare 38 parthenogenetic lineages and three field collections of aphids of the Myzus persicae (Sulzer) group sampled on peach and tobacco in the Caserta region of southern Italy. Comparisons were also made with the morphology of lineages collected on peach in Lehonia, in central eastern Greece away from tobacco-growing regions, and on tobacco in Naphplion, in southern Greece. The lineages were measured after parthenogenetic rearing for one to three generations on the same host (potato) under constant conditions. As in previous work, the multivariate morphometric approach separated the aphids from peach from those feeding on tobacco. The life cycle category of the lineages was also examined. Almost all the lineages from peach in Caserta were holocyclic, yet the lineages from tobacco in the same region were unable to produce sexual morphs. The results suggest that tobacco-adapted and non-tobacco-adapted forms co-exist in the same region in southern Italy, not only because they colonize different host plants, but also because they have different life cycles. This is in complete contrast to the situation in peach-growing areas of northern Greece, and shows that the ecology and population structure of M. persicae is different in neighbouring counties of the Mediterranean area, even where climatic conditions and cultivated crops are similar

Biological characteristics of the mirids Macrolophus costalis and Macrolophus pygmaeus preying on the tobacco form of Myzus persicae (Hemiptera : Aphididae)

Biological and population parameters of the predatory bugs Macrolophus costalis Fieber and Macrolophus pygmaeus Rambur preying on the tobacco aphid Myzus persicae (Sulzer) were examined. Tobacco was used as host plant and all experiments were carried out at 23degreesC and L16:D8. In M. costalis, the developmental time for eggs and the total duration of nymphal instars was 13.1 and 22.2 days and in M. pygmaeus 13.0 and 20.2 days, respectively. Both species completed their nymphal development feeding only on plant juices although they required significantly more time to attain adulthood than when feeding on prey. The longevity of M. costalis females and the preoviposition period were 49.9 and 5.6 days and those of M. pygmaeus were 50.3 and 6.3 days, respectively. Adult males showed a higher longevity than females in both species. The intrinsic rate of increase and the mean total number of eggs laid were 0.0644 and 121 in M. costalis and 0.0615 and 104 in M. pygmaeus, respectively Mean total aphid consumption by nymphs of M. costalis was 61 aphids, about twice that of M. pygmaeus (37 aphids). Total aphid consumption by a male and female pair of M. costalis and M. pygmaeus until the death of the female was 244 and 285 aphids, respectively. The results of the study are discussed in relation to the impact of the two predatory bugs on tobacco aphid populations

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 20degreesC 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

Genetic diversity and insecticide resistance during the growing season in the green peach aphid (Hemiptera: Aphididae) on primary and secondary hosts: a farm-scale study in Central Chile

The seasonal dynamics of neutral genetic diversity and the insecticide resistance mechanisms of insect pests at the farm scale are still poorly documented. Here this was addressed in the green peach aphid Myzus persicae (Sulzer) (Hemiptera: Aphididae) in Central Chile. Samples were collected from an insecticide sprayed peach (Prunus persica L.) orchard (primary host), and a sweet-pepper (Capsicum annum var. grossum L.) field (secondary host). In addition, aphids from weeds (secondary hosts) growing among these crops were also sampled. Many unique multi-locus genotypes were found on peach trees, while secondary hosts were colonized mostly by the six most common genotypes, which were predominantly sensitive to insecticides. In both fields, a small but significant genetic differentiation was found between aphids on the crops vs. their weeds. Within-season comparisons showed genetic differentiation between early and late season samples from peach, as well as for weeds in the peach orchard. The knock-down resistance (kdr) mutation was detected mostly in the heterozygote state, often associated with modified acetylcholinesterase throughout the season for both crops. This mutation was found in high frequency, mainly in the peach orchard. The super-kdr mutation was found in very low frequencies in both crops. This study provides farm-scale evidence that the aphid M. persicae can be composed of slightly different genetic groups between contiguous populations of primary and secondary hosts exhibiting different dynamics of insecticide resistance through the growing season

Effect of temperature on development, growth and feeding of Coccinella septempunctata and Hippodamia convergens reared on the tobacco aphid, Myzus persicae nicotianae

Preimaginal development, mortality, aphid consumption rate, and size and weight upon reaching the adult stage of the aphidophagous coccinellids Hippodamia convergens Guerin-Meneville and Coccinella septempunctata L. collected from Karditsa, central Greece, were examined at four constant temperatures ( 14, 17, 20 and 23 degrees C) and L16: D8. The coccinellids fed on the tobacco aphid, Myzus persicae nicotianae Blackman. Egg, larval and pupal mortality was highest at 14 degrees C reaching 85.0, 73.8 and 29.4% in H. convergens and 49.3, 75.4 and 58.8% in C. septempunctata, respectively. Total preimaginal development ranged from 57.2 to 70.4 days at 14 degrees C, and to 16.9 and 22.1 days at 23 degrees C in H. convergens and C. septempunctata, respectively. Heavier and larger adults of H. convergens were obtained at 17 and 20 degrees C. In C. septempunctata temperature did not affect adult weight while the lowest size was observed at 14 and 17 degrees C. Day-degrees requirements for preimaginal development in H. corvengens were 212.9 above a developmental threshold of 11.0 degrees C. The corresponding values for C. septempunctata were 281.5 and 10.7 degrees C. In H. convergens total and daily aphid consumption ranged from 46.8 aphids at 14 degrees C to 85.0 aphids at 23 degrees C and from 1.5 aphids at 14 degrees C to 9.2 aphids at 23 degrees C, respectively. The corresponding values for C. septempunctata were 112.0 and 2.7 at 14 degrees C and 157.7 and 12.4 at 23 degrees C. The results show the high potential of both predators as biological control agents against the tobacco aphid. The knowledge obtained could be essential for their appropriate use and for the improvement of mass rearing systems

Genetic variation of Marchalina hellenica (Hemiptera: Margarodidae) sampled from different hosts and localities in Greece

Random amplified polymorphic DNA (RAPD) analysis was applied to 120 individuals of Marchalina hellenica (Gennadius) representing six populations collected in northern, central and southern mainland Greece. One population was sampled on one species of fir tree and the others on two species of pine trees. Four random decamer primers were used to evaluate genetic variation among the populations examined. The results revealed intra- and interpopulation polymorphism both related to host type and region of origin. Phylogenetic analysis based on genetic distances estimated by the RAPD frequencies revealed an important genetic differentiation in samples collected on fir trees in southern Greece and to a lesser extent in samples from pine trees in central and northern Greece. Furthermore, considerable subdivision and restricted gene flow among the populations examined were observed. The results are discussed in relation to the biology and geographical distribution of M. hellenica in Greece