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Uri Gerson - One of the best experts on this subject based on the ideXlab platform.
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karyotype and the sex determining mechanism of the mite hemisarcoptes Coccophagus meyer acarifomes astigmata hemisarcoptidae
International Journal of Acarology, 1995Co-Authors: Sergey Izraylevich, Uri Gerson, M WysokiAbstract:Abstract Hemisarcoptes Coccophagus Meyer (Acariformes: Astigmata: Hemisarcoptidae) is a parasite of armored scale insects (Homoptera: Diaspididae). This mite can adjust the sex ratio of its progeny. We found that H. Coccophagus has a diploid karyotype with 2n=14 in both sexes; the sex determining mechanism is either diplo-diploidy or parahaploidy. This provides one of the few examples, and the first in the Acariformes, of a non-arrhenotokous arthropod genetic system with the ability of facultative sex ratio adjustment.
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sex ratio of hemisarcoptes Coccophagus a mite parasitic on insects density dependent processes
Oikos, 1995Co-Authors: Sergey Izraylevich, Uri GersonAbstract:Hemisarcoptes Coccophagus Meyer (Acari : Astigmata : Hemisarcoptidae) is an obligate parasite of armoured scale insects (Homoptera : Diaspididae). We tested the following hypotheses : (1) the sex ratio of H. Coccophagus is affected by its population density ; (2) this effect is due to an asymmetric performance and dispersal of males and females at different density levels ; (3) the effect of density on sex ratio depends on the developmental stage of the mite exposed to it. Sex ratio (proportion of females) of H. Coccophagus adults in the field fluctuated between male and female biases and was negatively correlated with mite density. Laboratory experiments showed that during immature development mite survival and sex ratio decreased with increasing density, indicating that at high density levels immature females suffered higher mortality than males. At high density levels females, but not males, had smaller bodies and forelegs (which, according to the host-quality model, may affect the sex allocation decision of reproducing females). Longevity of adult males at low density was higher than that of females, while at high density, and while starving, females lived longer. Adult dispersal was affected by density : both sexes stayed on their hosts when density was low, while at high density levels females dispersed more than males. We conclude that population density may cause fluctuations in the sex ratio of H. Coccophagus in either male or female directions, depending on the density level and on the mite stages exposed to its influence. The operative function underlying the effect of population density on the sex ratio might be intraspecific competition.
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spatial patterns of the parasitic mite hemisarcoptes Coccophagus astigmata hemisarcoptidae host effect density dependence of aggregation and implications for biological control
Bulletin of Entomological Research, 1995Co-Authors: Sergey Izraylevich, Uri GersonAbstract:The spatial distribution of the parasitic mite Hemisarcoptes Coccophagus Meyer on two armoured scale insects (Homoptera: Diaspididae) was highly aggregated in the field. Mites were more aggregated on young than on ovipositing host scale females. No differences in the mite's distribution pattern were found between latania scale (Hemiberlesia lataniae (Signoret)) and oleander scale (Aspidiotus nerii (Bouche)). Mite aggregation was density-dependent on ovipositing host females (the degree of overdispersion decreased as mite abundance increased), but density-independent on young females. The effect of density-dependent and independent mite aggregation on the proportion of hosts escaping attack at different parasite abundances was simulated, and its relevance to biological control of Diaspididae is discussed.
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population dynamics of hemisarcoptes Coccophagus meyer astigmata hemisarcoptidae attacking three species of armored scale insects homoptera diaspididae
Experimental and Applied Acarology, 1993Co-Authors: Sergey Izraylevich, Uri GersonAbstract:The parasitic miteHemisarcoptes Coccophagus Meyer (Astigmata: Hemisarcoptidae) feeds on armored scale insects (Homoptera: Diaspididae). Three host scales were studied: chaff scale (Parlatoria pergandii Comstock andP. cinerea Hadden) infesting citrus (grapefruit and orange) orchards, latania scale [Hemiberlesia lataniae (Signoret)] and olcander scale (Aspidiotus nerii Bouche) occurring on acacia (Acacia cyanophylla) branches and leaves. The overall dynamics of mite populations were similar on the different scale species, although the level of attack on each sampled diaspidid host was different. Rates of young mite stages were highly variable on all three hosts throughout the sampling period while adult rates were stable, constituting around 20% of all mites. No oviposition by mites occurred in mid-winter on any scale species, on any plants or parts, at all sampling sites. Of the three diaspidids, highest mite prevalence (parasitization rate) occurred on latania scale. Mite prevalence on oleander scale infesting mature leaves was higher than on young leaves.H. Coccophagus apparently first attacks latania scale on branches, it then disperses to the same host inhabiting mature leaves, from there to co-occurring oleander scale and finally to oleander scale infesting young leaves. Mite prevalence on chaff scale was influenced by host plants and climatic regions: in the Negev it was higher than in the coastal plain, with scales on grapefruit being more heavily attacked at the former site but not on coastal plain. Our data suggest thatH. Coccophagus prefers ovipositing scale females. The decreasing order of preference for other scale stages was: young females immature males, 2nd-instar nymphs females.
Sergey Izraylevich - One of the best experts on this subject based on the ideXlab platform.
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karyotype and the sex determining mechanism of the mite hemisarcoptes Coccophagus meyer acarifomes astigmata hemisarcoptidae
International Journal of Acarology, 1995Co-Authors: Sergey Izraylevich, Uri Gerson, M WysokiAbstract:Abstract Hemisarcoptes Coccophagus Meyer (Acariformes: Astigmata: Hemisarcoptidae) is a parasite of armored scale insects (Homoptera: Diaspididae). This mite can adjust the sex ratio of its progeny. We found that H. Coccophagus has a diploid karyotype with 2n=14 in both sexes; the sex determining mechanism is either diplo-diploidy or parahaploidy. This provides one of the few examples, and the first in the Acariformes, of a non-arrhenotokous arthropod genetic system with the ability of facultative sex ratio adjustment.
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sex ratio of hemisarcoptes Coccophagus a mite parasitic on insects density dependent processes
Oikos, 1995Co-Authors: Sergey Izraylevich, Uri GersonAbstract:Hemisarcoptes Coccophagus Meyer (Acari : Astigmata : Hemisarcoptidae) is an obligate parasite of armoured scale insects (Homoptera : Diaspididae). We tested the following hypotheses : (1) the sex ratio of H. Coccophagus is affected by its population density ; (2) this effect is due to an asymmetric performance and dispersal of males and females at different density levels ; (3) the effect of density on sex ratio depends on the developmental stage of the mite exposed to it. Sex ratio (proportion of females) of H. Coccophagus adults in the field fluctuated between male and female biases and was negatively correlated with mite density. Laboratory experiments showed that during immature development mite survival and sex ratio decreased with increasing density, indicating that at high density levels immature females suffered higher mortality than males. At high density levels females, but not males, had smaller bodies and forelegs (which, according to the host-quality model, may affect the sex allocation decision of reproducing females). Longevity of adult males at low density was higher than that of females, while at high density, and while starving, females lived longer. Adult dispersal was affected by density : both sexes stayed on their hosts when density was low, while at high density levels females dispersed more than males. We conclude that population density may cause fluctuations in the sex ratio of H. Coccophagus in either male or female directions, depending on the density level and on the mite stages exposed to its influence. The operative function underlying the effect of population density on the sex ratio might be intraspecific competition.
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spatial patterns of the parasitic mite hemisarcoptes Coccophagus astigmata hemisarcoptidae host effect density dependence of aggregation and implications for biological control
Bulletin of Entomological Research, 1995Co-Authors: Sergey Izraylevich, Uri GersonAbstract:The spatial distribution of the parasitic mite Hemisarcoptes Coccophagus Meyer on two armoured scale insects (Homoptera: Diaspididae) was highly aggregated in the field. Mites were more aggregated on young than on ovipositing host scale females. No differences in the mite's distribution pattern were found between latania scale (Hemiberlesia lataniae (Signoret)) and oleander scale (Aspidiotus nerii (Bouche)). Mite aggregation was density-dependent on ovipositing host females (the degree of overdispersion decreased as mite abundance increased), but density-independent on young females. The effect of density-dependent and independent mite aggregation on the proportion of hosts escaping attack at different parasite abundances was simulated, and its relevance to biological control of Diaspididae is discussed.
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population dynamics of hemisarcoptes Coccophagus meyer astigmata hemisarcoptidae attacking three species of armored scale insects homoptera diaspididae
Experimental and Applied Acarology, 1993Co-Authors: Sergey Izraylevich, Uri GersonAbstract:The parasitic miteHemisarcoptes Coccophagus Meyer (Astigmata: Hemisarcoptidae) feeds on armored scale insects (Homoptera: Diaspididae). Three host scales were studied: chaff scale (Parlatoria pergandii Comstock andP. cinerea Hadden) infesting citrus (grapefruit and orange) orchards, latania scale [Hemiberlesia lataniae (Signoret)] and olcander scale (Aspidiotus nerii Bouche) occurring on acacia (Acacia cyanophylla) branches and leaves. The overall dynamics of mite populations were similar on the different scale species, although the level of attack on each sampled diaspidid host was different. Rates of young mite stages were highly variable on all three hosts throughout the sampling period while adult rates were stable, constituting around 20% of all mites. No oviposition by mites occurred in mid-winter on any scale species, on any plants or parts, at all sampling sites. Of the three diaspidids, highest mite prevalence (parasitization rate) occurred on latania scale. Mite prevalence on oleander scale infesting mature leaves was higher than on young leaves.H. Coccophagus apparently first attacks latania scale on branches, it then disperses to the same host inhabiting mature leaves, from there to co-occurring oleander scale and finally to oleander scale infesting young leaves. Mite prevalence on chaff scale was influenced by host plants and climatic regions: in the Negev it was higher than in the coastal plain, with scales on grapefruit being more heavily attacked at the former site but not on coastal plain. Our data suggest thatH. Coccophagus prefers ovipositing scale females. The decreasing order of preference for other scale stages was: young females immature males, 2nd-instar nymphs females.
Shaaban Abd-rabou - One of the best experts on this subject based on the ideXlab platform.
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Notes on the Parasitoids of the Soft Brown Scale, Coccus Hesperidum (Hemiptera: Coccidae) in Egypt
2016Co-Authors: Shaaban Abd-rabou, A. Anafi, Nemmat A. HusseinAbstract:NOTES ON THE PARASITOIDS OF THE SOFT BROWN SCALE, COCCUS HESPERIDUM (HEMIPTERA: COCCIDAE) IN EGYPT. Thirteen species of hymenopterous parasitoid were found in association with Coccus hesperidum at three locations in Egypt: 4 species of Aphelinidae (of which three were recorded for the first time); seven species of Encyrtidae (of which three were recorded for the first time), the first record of a species of Mymaridae, plus a species of Pteromalidae. The relative abundance of these parasitoids is discussed. Key words: survey, rearing methods, percentage parasitism, Coccophagus, Marietta, Diversinervis, Metaphycus, Microterys, Parachthrodryinus, Prochilonerus, Alaptus, Scutellista.
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Coccophagus scutellaris (Hymenoptera: Aphelinidae): A Highly Effective Biological Control Agent of Soft Scale Insects (Hemiptera: Coccidae) in Egypt
Psyche: A Journal of Entomology, 2011Co-Authors: Shaaban Abd-rabouAbstract:About 953000 individuals of the cosmopolitan parasitoid, Coccophagus scutellaris (Dalman) (Hymenoptera: Aphelinidae), were released and evaluated during 2009-2010 for the control of the following soft scale insects (Hemiptera: Coccidae) infesting the following economic crops in Egypt: Ceroplastes rusci on citrus in Beni Seuf, Ceroplastes floridensis Comstock on citrus in Gharbiya, Coccus hesperidum L. on guava in Giza, Pulvinaria floccifera (Westwood) on mango in Sharqiya, Pulvinaria psidii Maskell on mango in Ismailia, Saissetia coffeae (Walker) on olive in Marsa Matruh, and Saissetia oleae (Oliver) on olive in the Northern Coast. The population of C. scutellaris showed a significant correlation with the build up of the population of the soft scale insects population in all of the release sites studied. The maximum rate of parasitism of the other species of parasitoids associated with soft scale insects at the release sites decreased after the release of C. scutellaris.
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Importation, colonization and establishment of Coccophagus cowperi Gir. (Hymenoptera: Aphelinidae) on Saissetia coffeae (Walk.)(Homoptera: Coccidae) in Egypt
Journal of Pest Science, 2005Co-Authors: Shaaban Abd-rabouAbstract:The hemispherical soft scale, Saissetia coffeae (Walker) (Homoptera: Coccidae), is one of the most important pests attacking olive trees in Egypt. During the period 2001–2003, a total of about 300,000 individuals of the parasitoid Coccophagus cowperi Girault (Hymenoptera: Aphelinidae), obtained from India, was released at 35 sites for the biological control of S.coffeae on olive trees in Egypt. The maximum parasitism rates reached 53 and 62%, while average parasitism rates were 17.2 and 30.8% in the Marsy Mattrouh and El-Arish locations, respectively. These results indicate establishment of this parasitoid on this important economic plant in Egypt.
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THE ROLE OF Coccophagus SCUTELLARIS (HYMENOPTERA: APHELINIDAE) IN THE BIOLOGICAL CONTROL OF SOFT SCALE INSECTS (HOMOPTERA: COCCIDAE) IN EGYPT
Insect Science, 2002Co-Authors: Shaaban Abd-rabouAbstract:Coccophagus scutellaris (Dalman) is one of the specific parasitoids that attack soft scale insects in Egypt. In the present study, C. scutellaris was reared from 6 species of soft scale insects. These are Ceroplastes flori-densis Comstock, Coccus hesperidum L., Pulvinaria floccgera (Westwood), P. psidii Maskell, Saissetia coffeae (Walker) and S. oleae (Oliver). The abundance of C. scutellaris was monitored from July to Nov. 1999–2000 in five localities in Egypt, the Beni-Suef, Cairo, Giza, Gharbiya and the Northern coast. C. scutellaris is considered an effective parasitoid of S. coffeae and S. oleae with maximum parasitism rates reaching 26% and 22% in Nov. and Aug. 1999, respectively.
J. G. Charles - One of the best experts on this subject based on the ideXlab platform.
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releases of hemisarcoptes Coccophagus meyer acari hemisarcoptidae a predator of armoured scale insects in the south island
New Zealand Entomologist, 1998Co-Authors: J. G. Charles, D. J. Allan, C H Wearing, G M Burnip, P W ShawAbstract:Hemisarcoptes Coccophagus Meyer were released into apple, pear and plum trees infested with Quadraspidiotus perniciosus (Comstock), Q. ostreaeformis (Curtis) and/or Lepidosaphes ulmi (L.) in Nelson, Mid-Canterbury and Central Otago between 1991 and 1996. They were recovered from only one property in Nelson (on Q. perniciosus on pear) up to 12 months after the initial release, but not 6 years later. H. Coccophagus developed successfully on Q. perniciosus in the laboratory. Possible reasons for the apparent failure of the mite to establish are discussed.
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Introduction of armoured scale predators and establishment of the predatory mite Hemisarcoptes Coccophagus (Acari: Hemisarcoptidae) on latania scale, Hemiberlesia lataniae (Homoptera: Diaspididae) in kiwifruit shelter trees in New Zealand.
Bulletin of Entomological Research, 1993Co-Authors: M. G. Hill, D. J. Allan, R. C. Henderson, J. G. CharlesAbstract:Between 1987 and 1989, three predatory beetle species ( Chilocorus bipustulatus (Linnaeus), C. infernalis (Linnaeus) and C. cacti (Linnaeus)) (Coleoptera: Coccinellidae) and two predatory mite species ( Hemisarcoptes Coccophagus Meyer and H. cooremani Thomas) were imported and released for the biological control of armoured scale insects ( Hemiberlesia rapax Comstock, H. lataniae Signoret and Aspidiotus nerii Bouche ) on kiwifruit and shelter trees in New Zealand. Hemisarcoptes Coccophagus has established on Hemiberlesia lataniae infestations on Lombardy poplar ( Populus nigra var. Italica) shelter trees at three sites. Detailed studies at one of the release sites over a period spanning nine to 24 months after release, showed that densities of Hemiberlesia lataniae in samples with mites fell to less than 20% of the level in control trees. Assessment of the dispersion characteristics of the mite suggested that the adults are repelled by the presence of other mites on a host. Hemisarcoptes Coccophagus can use two species of New Zealand ladybirds ( Scymnus fagus Broun and Halmus chalybeus Boisduval) for phoresy. Hemisarcoptes Coccophagus spread naturally to the control trees between 20 and 24 months after release, though the means of dispersal between trees is not known.
U. Gerson - One of the best experts on this subject based on the ideXlab platform.
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Frequency-dependent host selection by parasitic mites: a model and a case study
Oecologia, 1995Co-Authors: S. Izraylevich, O. Hasson, U. GersonAbstract:Previous studies on frequency-dependent food selection (changing food preferences in response to changes in relative food abundance) have focused on predators and parasitoids. These organisms utilize several victims during their lifetime. We introduce the case of parasites which, having accepted a host, do not change it. We propose two alternative models to explain the biased occurrence of parasites on different host types: (1) through the option of rejecting less-preferred hosts prior to accepting one of them; (2) by differential parasite survival on different host types. These models predict that host rejection, but not differential survival, can create frequency-dependent parasitism (FDP). Unlike previously described factors responsible for frequency dependence of food selection, which act through changing the foraging behaviour of individual predators or parasitoids, FDP involves no adjustment of parasite foraging strategy according to previous feeding experience. The mite Hemisarcoptes Coccophagus is an obligate parasite of armoured scale insects (Homptera: Diaspididae). Our field data show that H. Coccophagus is found more frequently on ovipositing than on young host females. Our model, combining the effects of host rejection and differential survival, is used to estimate the relative contribution of these factors to parasite biased occurrence on different hosts. The contribution of differential survival was dominant in H. Coccophagus , and overode any effect of host rejection. Nevertheless, our prediction that FDP may be found in parasites is supported by literature data about a parasitic water mite.
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The hypopus of Hemisarcoptes Coccophagus : distribution and apolysis
Acarologia, 1995Co-Authors: S. Izraylevich, U. GersonAbstract:On a observe une distribution Hemisarcoptes contagieuse des hypopodes (deutonymphes) de Hemisarcoptes Coccophagus Meyer (Astigmata : Hemisarcoptidae), un parasite des pucerons a bouclier (Homoptera : Diaspididae), lors de leur dispersion sur leur vecteur, Chilocorus bipustulatus (L.) (Coleoptera : Coccinellidae). Lorsqu'elles figurent en petit nombre, la plupart des deutonymphes s'agglomerent sur une des elytres de la coccinelle, alors qu'en plus grand nombre elles se repartissent de facon egale sur les deux elytres. Les hypopodes preferent de loin s'attacher aux marges subelytrales, et plus particulierement a leurs parties anterieures-laterales. Ces zones manquent de microsetae qui abondent au centre des elytres. Les deutonymphes sont incapables de terminer leur ontogenese sans sejourner un minimum de 48 heures sous les elytres du vecteur. Le temps de contact ideal avec les coccinelles est de 4 a 6 jours et cette periode induit a peu pres 30 % de mues hypopodiales. Les pucerons hotes ne sont pas necessaires a l'apolyse, mais leur presence accroit le taux de reussite des mues des deutonymphes. On discute la signification de ces resultats afin d'augmenter l'efficacite des lâchers d'acariens dans les champs.