Two new species of aphids (Homoptera: Aphididae) from North-west India

Two new aphids viz. Prociphilus (Stagona) himalayaensis sp. nov. infesting the roots of Pinus excelsa and an unidentified plant and Capitophorus tricholepidis sp. nov. infesting Tricholepis furcata, collected from Simla Himalayas and Kumaon Himalayas, respectively, of the North-west India are described.     

Physiological modification of the host feeding site by cereal aphids (Homoptera: Aphididae)

Indole-3-acetic acid-l-14C and 14C-sucrose labels were used to study the effects of greenbugs, Schizaphis graminum (Rondani), and Russian wheat aphids, Diuraphis noxia (Mordvilko), on phloem function of wheat (Triticum aesticum L.). Greenbug feeding significantly reduced translocation from the immediate feeding site; however, phloem integrity was not impeded. In contrast, Russian wheat aphids had little effect on vein loading or phloem translocation at the feeding site. Similar results were obtained when resistant and susceptible wheats were infested with three different greenbug biotypes. Greenbugs fed artificial diets containing 14C-sucrose injected salivary material that was translocated to both root and shoot systems. The accumulation of salivary constituents in the roots of wheat seedlings fed upon by greenbugs may account for the significant reductions in root biomass that have previously been reported.     

A new genus and two new species of aphids (Homoptera: Aphididae) from north-west India

A new aphid genus Raychaudhuriella and two new specices viz. Raychaudhuriella myzaphoides and Rhopalosiphoninus sensoriatus are described from Himachal Pradesh, north-west Himalaya. The affinity of Raychaudhuriella gen. nov. is drawn with Aspidophorodon Verma, Cavariela del Guercio, Myazphis van der Goot, Tricaudatus Narzikulov and Vesiculaphis del Guercio. Figures and biometrical data of the new species have been provided.     

Molecular systematics of aphids (Homoptera: Aphididae): new insights from the long-wavelength opsin gene

Viviparous aphids (Aphididae) constitute a monophyletic group within the Homoptera with more than 4000 extant species worldwide but higher diversity in temperate regions. Several aspects of their biology account for attention paid to this group of insects. Their plant-sap-sucking way of feeding with many species transmitting viruses to crop plants has important implications on crop management strategies. Cyclical parthenogenesis associated in many groups to host alternation and elaborate polyphenisms is of special interests for evolutionists. Finally, the ancient association of most aphid species with intracellular endosymbiotic bacteria (Buchnera sp.) has also received much attention from evolutionists interested in mechanisms involved in the symbiotic process. Knowing the phylogenetic relationships among major aphid taxa is of special interest to evolutionists interested in the above issues. However, until recently, molecular approaches to aphid phylogeny were absent and discussions on the evolution of aphid life-cycles and on evolutionary aspects of their symbiotic association with Buchnera were framed by morphology-based phylogenies. Recently, two reports using molecular approaches attempted to address the yet unresolved phylogeny of Aphididae with limited although somehow different conclusions. In the present report we study the utility of the long-wave opsin gene in resolving phylogenetic relationships among seven subfamilies within the Aphididae. Our results corroborate some previously proposed relationships and suggest a revision of some others. In particular, our data support grouping the analysed aphid species into three main clades, being the subfamily Lachninae one of them, which contradicts its generally accepted sistership relationship with the subfamily Aphidinae. Moreover, our data also suggest a basal position of Lachninae which has implications on current discussions about the ancestrality of conifer-feeding in modern aphids.     

Seasonal dynamics of cereal aphids on Russian wheat aphid (Homoptera: Aphididae) susceptible and resistant wheats

Field experiments were conducted in 1997 and 1998 to evaluate the impact of resistance to Russian wheat aphid, Diuraphis noxia (Mordvilko), on the cereal aphid complex in wheat. Two spring wheats were planted: the variety "Centennial" (Russian wheat aphid susceptible) and the advanced line IDO488 (Russian wheat aphid resistant). IDO488 incorporates the resistance found in PI 294994 into a Centennial background. Field plots were artificially infested with adult D. noxia and sampled weekly. The most abundant aphid species in 1997 were Metopolophium dirhodum (Walker), Sitobion avenae (F.), D. noxia, and Rhopalosiphum padi (L.). In 1998, the order of abundance was M. dirhodum, R. padi, S. avenae, and D. noxia. The resistant genotype had significantly fewer D. noxia than the susceptible one during both years. However, plant genotype had no significant effect on the other aphid species in either year. Both the initial density of D. noxia and plant growth stage, had a significant effect on D. noxia population development, but had no effect on the other aphid species. There was no interaction between D. noxia resistance and the population density of the other aphid species observed.     

Clonal turnover of MACE-carrying peach-potato aphids (Myzus persicae (Sulzer), Homoptera: Aphididae) colonizing Scotland

Peach-potato aphids, Myzus persicae (Sulzer), collected in Scotland in the years 1995 and 2002-2004 were characterized using four microsatellite loci and three insecticide resistance mechanisms. From 868 samples, 14 multilocus genotypes were defined (designated clones A-N). Five of these (denoted A, B, H, M and N) carried modified acetylcholinesterase (MACE) resistance, the most recent resistance mechanism to have evolved in M. persicae. The current paper shows that the continued presence of MACE aphids is due to turnover, as clones A and B were replaced in field samples by clones H, M and N in later seasons. Thus, insecticide-resistant populations in Scotland can be attributed to multiple waves of rapid clone colonisations and not to the continued presence of stable resistant clones or mutation or sexual recombination in local populations. The MACE clones carried varying levels of the other insecticide resistance mechanisms, kdr and esterase. The presence of these mechanisms could alter the clones success in the field depending on insecticide spraying (positive selection) and resistance fitness costs (negative selection).     

Secondary intracellular symbiotic bacteria in aphids of the genus Yamatocallis (Homoptera: Aphididae: Drepanosiphinae).

A novel secondary intracellular symbiotic bacterium from aphids of the genus Yamatocallis (subfamily Drepanosiphinae) was characterized by using molecular phylogenetic analysis, in situ hybridization, and diagnostic PCR detection. In the aphid tissues, this bacterium (tentatively designated YSMS [Yamatocallis secondary mycetocyte symbiont]) was found specifically in large cells surrounded by primary mycetocytes harboring Buchnera cells. Of nine drepanosiphine aphids examined, YSMS was detected in only two species of the same genus, Yamatocallis tokyoensis and Yamatocallis hirayamae. In natural populations of these aphids, YSMS was present in 100% of the individuals. Phylogenetic analysis based on 16S ribosomal DNA (rDNA) sequences demonstrated that YSMS of Y. tokyoensis and Y. hirayamae constitute a distinct and isolated clade in the gamma subdivision of the class Proteobacteria. No 16S rDNA sequences of secondary endosymbionts characterized so far from other aphids showed phylogenetic affinity to YSMS. Based on these results, I suggest that YSMS was acquired by an ancestor of the genus Yamatocallis and has been conserved throughout the evolution of the lineage. By using the nucleotide substitution rate for 16S rDNA of Buchnera spp., the time of acquisition of YSMS was estimated to be about 13 to 26 million years ago, in the Miocene epoch of the Tertiary period.     

Resistance of cereals to aphids: Interaction between hydroxamic acids and the aphid Sitobion avenae (Homoptera: Aphididae)

The hydroxamic acids in the seedlings of four varieties of winter wheat were extracted initially in boiling methanol in order to avoid enzymatic hydrolysis. The increase in numbers of aphids on these varieties of wheat were recorded. HPLC analysis of hydroxamic acids in the extracts showed the presence of DIMBOA-glucoside, DIMBOA-aglucone and its benzoxazolinone (MBOA). There was a highly significant negative correlation between the concentration of DIMBOA-aglucone in the seedlings and aphid performance. However, the association between aphid performance and DIMBOA-aglucone in the tips of the seedlings was weaker. In general aphid infestation of wheat seedlings slightly increased the concentration of all the hydroxamic acid derivatives. Moreover, aphids ingested hydroxamic acids and were able to detoxify some of the DIMBOA-aglucone they ingested.     

On the processes shaping reproductive isolation in aphids of the Aphis fabae (Scop.) complex (Aphididae: Homoptera)

Models of sympatric speciation for phytophagous insects are based on the premise that ecological specialization on different host plants can indirectly result in significant reproductive isolation. A candidate example of host plant shift is provided by the partially reproductively-isolated aphids Aphis fabae fabae and A. f. mordwilkoi , which utilize different hosts for sexual reproduction. However, unexpected isolation based on mating behaviour was found for these two aphids. In olfactometer trials, males responded to the pheromones of females of both subspecies when presented a subspecies in isolation but preferentially to females of the same subspecies in choice tests. On contact, the incidence or duration of between-subspecies copulations was significantly lower than same-subspecies copulations, and spermatozoa were transferred during 88% of the same-subspecies copulations, but only 19% of between-subspecies copulations. These data are indicative of strong pre-zygotic isolation between the subspecies. Complementary restriction analysis of mitochondrial DNA and a plasmid (pAFE/eu) in an obligate symbiotic bacterium (Buchnera) revealed a paraphyletic relationship among four subspecies of A. fabae (A. f. fabae, A. f mordwilkoi, A. f cirsiiacanthoidis and A. f. solanella). We discuss how the lack of clear genetic differentiation between A. f. fabae and A. f. mordwilkoi , despite substantial pre-zygotic isolation, may be a consequence of reinforcement.     

Microsatellite marker analysis of peach-potato aphids (Myzus persicae, Homoptera: Aphididae) from Scottish suction traps

The peach-potato aphid Myzus persicae (Sulzer) is an important vector of plant viruses. A network of suction traps collects aerial samples of this aphid in order to monitor and help predict its spatial distribution and likely impact on virus transmission in crops. A suction trap catch is thought to be a good representation of the total aphid pool. Sensitive molecular markers have been developed that determine the genetic composition of the M. persicae population. In Scotland, UK, these were applied to field collections revealing a limited number of clones. Molecular markers are less successful when applied to specimens that have been preserved in an ethanol-based trap fluid designed to preserve morphology. An assessment of different DNA extraction and PCR techniques is presented and the most efficient are used to analyse M. persicae specimens caught in the Dundee suction trap in 2001, a year when exceptionally high numbers were caught. The results reveal that the majority of the M. persicae caught belonged to two highly insecticide resistant clones. In addition, it was possible to compare the relative frequencies of genotypes caught in the trap with those collected at insecticide treated and untreated field sites in the vicinity. These results indicate that, in addition to suction trap data, the ability to sample field sites provides valuable early warning data which have implications for pest control and virus management strategies.     

The compositoin of cuticular hydrocarbons of the cereal aphids Sitobion avenae F. (Homoptera,Aphididae)

• 1.1. The cuticular hydrocarbons of the cereal aphids, Sitobion avenae F. were studyed by capillary column chromatography and mass spectrometry.
• 2.2. n-Alkanes, 2-, 3-, 4-, 5-, 6-, 10-, 11-, 12- and 13-monomethylalkanes, 7,11-, 11,15-, 13,17- and 5,11-dimethylalkanes were found in cuticular lipids.
• 3.3. The results obtained are significantly different from these of pea aphid, where only n-alkanes were found.
• 4.4. The n-alkanes of cereal aphids range from 23 to 35 carbon atoms with the predominance of odd over even members.
• 5.5. These are terminally branched hydrocarbons 2-methyl and 3-methyl-alkanes rarely found together in cuticular lipids of insects.

     

Plant washing as a pest management technique for control of aphids (Homoptera: Aphididae).

Changes in aphid presence following plant washings were evaluated on hibiscus plants, Hibiscus rosa-sinensis L., that supported natural aphid infestations--primarily melon aphid, Aphis gossypii Clover. Type of plant module (such as stems, tight buds, open flowers, and sepal caps) and percent of module's surface covered by aphids were recorded for each branch tip on every plant. Plant washing was done with tap water, applied for 30 s three times a week for 3 wk. Aphid presence was recorded each week. Aphid presence on plant structures immediately before and after a single 30-s wash treatment was also examined. In the 3-wk study, mean percent coverage of plant parts with aphids was significantly affected by wash treatment, plant module type, and their interactions, as well as by time and the interaction of time with wash treatment. By the third week, unwashed plants had 33.1% of stems and branch tips scoring >5% coverage with aphids, and 17.9% of unwashed stems and branch tips had 20% or more of their surface area covered by aphids. Washing plants prevented aphid coverage from ever exceeding the 5% class on all module types. In the second experiment, buds and stems with high numbers of aphids before washing generally experienced notable declines with a single wash. When the prewash coverage was 10% or greater, reduction in coverage ranged from 50 to 100% of the prewash amount. In 64% of the cases, the reduction in coverage was 75% or more of the prewash amount. Plant washing can provide a viable means of management for small, soft-bodied arthropods such as aphids.     

Gum cordia effectively enhances foliage adhesion of neem oil and increases its efficacy against aphids (Homoptera: Aphididae)

The efficiency of pesticides is greatly affected by their ability to adhere and retain on foliage surface. Neem oil, though a very well-known source of many biologically active pesticidal compounds, is very sensitive to environmental parameters, such as UV light. Also, due to volatilization, it is lost in environment and hence fail to reach target and show activity. In this study we attempted to stabilize neem oil emulsion and increase its retention on foliage surface by adding varying concentration of gum cordia. Gum cordia is an anionic polysaccharide derived from Cordia myxa fruits with strong adhesion and emulsification properties. The lethal concentration (LC₅₀) of the final formulations were also determined against aphid species Myzus persicae and Schizaphis graminum. Adhesion was found to be dependent on the concentration of gum cordia as well as type of crop. Increasing gum cordia in neem oil formulations resulted in increase in adhesion of the spray on the leaf surfaces and up to 6 times higher adhesion was observed with 0.5% gum cordia on mustard leaf compared to control. The LC₅₀ decreased with increasing gum cordia concentration. The LC₅₀ values of neem oil sprayed on mustard, spinach, and wheat leaves with 0.5% gum cordia were 0.205, 0.715, and 2.074% respectively while for neem oil control spray (with no gum cordia) LC₅₀ values were 1.833, 2.112, and 4.992% respectively for the above tested leaves. Presence of greater than 0.125% gum cordia in neem formulations provided the barrier against UV irradiation.     

A guide to the winged aphids (Homoptera) of Costa Rica

This guide is a compilation of limited morphological and biological information on the winged morphs of 60 species of aphids that have been collected in Costa Rica. It should not be viewed as a definitive taxonomic treatise on the aphids of Costa Rica, rather it is a tool that can be used to assist in research on the biology, host plant relationships, taxonomy, and virus transmission capabilities of aphids. Each species is covered in an identical manner. Morphological and biological information is provided in both Spanish and English as well as photographs of slide mounted specimens. Keys are provided to help the user in identifying the species. Most of the specimens examined were taken in traps associated with epidemiological studies. Limited field collecting has generated host records and these have been added to a list of the aphids of Central America that was compiled by Pamela Anderson and appended in the guide with her permission. The authors hope that this book will be useful to entomologists in Costa Rica and Central America.     

Variation for resistance to aphids (Homoptera: Aphididae) among tomato inbred backcross lines derived from wild Lycopersicon species

Two tomato inbred backcross line (IBL) populations, derived from crosses between aphid-susceptible Lycopersicon esculentum Mill. 'Peto 95-43' X resistant wild L. pennellii Corr (D'arcy) accession LA716, and Peto 95-43 X resistant wild L. hirsutum f. glabratum Mull accession LA407, were evaluated in replicated field experiments for resistance to potato aphid, Macrosiphum euphorbiae (Thomas), and green peach aphid, Myzus persicae (Sulzer). Aphid infestation scores for each IBL and control (LA716, LA407, Peto 95-43, and susceptible 'Alta') plot were recorded weekly for 5 and 9 wk during the summers of 2000 and 2001, respectively. Aphid infestation scores from leaflets were used to calculate area under the infestation pressure curve (AUIPC), a measure of aphid infestation throughout the growing season, for each IBL and control. Score AUIPC was highly correlated with actual aphid count AUIPC, indicating that scores accurately reflected aphid infestation. Score AUIPC was also highly correlated across both years (2000 and 2001) and locations. Low score AUIPC was significantly correlated with larger plant size and sprawling, indeterminate plant growth habit. Seven IBLs, LA716, and LA407 were significantly more resistant to aphids (lower score AUIPC) than susceptible parent Peto 95-43 in both years. Two IBLs, 1034 and 1051, were not significantly different from resistant LA407 for score AUIPC in both years. The seven aphid-resistant IBLs identified here can be useful as donor parent material for resistance breeding efforts in cultivated tomato.     

Effects of long-term storage at -14 degrees C on the survival of Neozygites fresenii (Entomophthorales: Neozygitaceae) in cotton aphids (Homoptera: Aphididae)

Neozygites fresenii-infected Aphis gossypii cadavers, containing dormant hyphal bodies of N. fresenii, were stored in 4 ml glass vials at -14 degrees C in a standard consumer-type refrigerator/freezer for 1, 21, 30, 43, 51, and 68 months to determine the effect of storage on fungal survival. When the cadavers were removed from the freezer and placed in 25+/-1 degrees C, 100% relative humidity, and 12:12 (L:D) conditions, N. fresenii survival, as shown by fungal sporulation from the cadavers, was high at all storage periods. The average percentage of cadavers from which the fungus sporulated were 93, 47, 100, 100, 80, and 60% from 1, 21, 30, 43, 51, and 68 months storage periods, respectively. The number of primary conidia discharged from each sporulating cadaver was estimated using a scale of 1 (low, ca. 1000 primary conidia), 2 (medium, ca. 2000 primary conidia) and 3 (high, ca. 3000 primary conidia). The median scores for the number of primary conidia produced per sporulating cadaver were 3, 2, 3, 3, 2.5, and 1 for 1, 21, 30, 43, 51, and 68 months, respectively. Therefore, except for the longest storage period, most cadavers produced medium to high numbers of primary conidia. Mean germination of primary conidia produced from N. fresenii-infected-aphid cadavers from each time period varied significantly from 66.3 to 86.1% in the 21 and 43 months categories, respectively. Infectivity of capilliconidia, produced from frozen N. fresenii, to live healthy cotton aphids varied significantly from 16.7 to 68.7% from cadavers stored 68 months and 1 month, respectively. Overall N. fresenii survived well in dried frozen cotton aphid cadavers for up to 6 years with little reduction in sporulation, numbers of spores produced, germination of primary conidia, or infectivity.     

Host preference by Allothrombium pulvinum (Acari: Trombidiidae) larvae on aphids: Macrosiphum rosae,Aphis gossypii and Hyalopterus amygdali (Homoptera: Aphididae)

In this study aphid-plant association and its effect on host preference of parasitic Allothrombium pulvinum larvae was examined with multiple-choice tests. Host species selection, host size selection and superparasitism with mite larvae were studied with two-choice tests. Three aphid species were used: Macrosiphum rosae, Aphis gossypii and Hyalopterus amygdali. In multiple-choice tests, larvae of A. pulvinum showed no significant preference for any aphid-plant association when given M. rosae on rose, A. gossypii on cucumber and H. amygdali on apricot simultaneously. Two-choice tests showed that larval mites preferred H. amygdali to A. gossypii, but had no preference when offered a choice between A. gossypii and M. rosae or between H. amygdali and M. rosae. In host size selection and superparasitism tests, significantly more mites selected the larger host (M. rosae). Furthermore, parasitised H. amygdali were preferred to unparasitised ones. This revised version was published online in July 2006 with corrections to the Cover Date.