Schizaphis Graminum Research Articles

Resistance of wheat cultivars and lines to Schizaphis graminum (Hemiptera: Aphididae) under laboratory conditions

Greenbug, Schizaphis graminum (Rondani), is a worldwide pest of cereals including rice, sorghum, wheat, barley, etc. The relative impact of resistance modalities, including antibiosis and antixenosis, and tolerance of seven wheat cultivars and lines (three wheat cultivars, namely Kouhdasht, Bezostaya and Hirmand, and four wheat lines, namely ERWYT 87-7, ERWYT 87-8, ERWYT 87-15 and ERWYT 87-16) with different levels of resistance against S. graminum was studied under laboratory conditions in Ardabil, Iran. In the antibiosis test, S. graminum produced the most and fewest progeny on Kouhdasht and ERWYT 87-16 in the reproduction period, respectively. In the tolerance test, ERWYT 87-16 and ERWYT 87-7 had the highest tolerance against S. graminum. However, in the antixenosis test, we did not detect any significant differences among tested cultivars and lines in terms of the number of adult aphids attracted to them. Overall, the plant resistance index (PRI) values were greatest for ERWYT 87-16 (4.95) and ERWYT 87-7 (4.11) and least for Hirmand (1.11) and Kouhdasht (1.20).

HYMENOPTEROUS PARASITOIDS ASSOCIATED WITH CEREAL APHIDS IN WHEAT FIELDS AT ASSIUT الطفيليات من رتبة غشائية الأجنحة المصاحبة لحشرات من النجيليات فى حقول القمح فى أسيوط

The present study was carried out in Assiut area to investigate the relationship between cereal aphids and their associated parasitoids on wheat plants during two successive seasons, 2011 and 2012. The results indicated that, of 48,000 mummified aphids collected from wheat plants in two seasons, 89.69% adult parasitoids were emerged. Ten parasitoid species belonging to five families of order hymenoptera were identified. The primary parasitoid species were recorded, Aphidius colemani Vereck, A. matricariae Haliday, Diaeretiella rapae (McIntosh), Ephedrus plagiator (Ness), Praon necans Mackauer and Trioxys sp., in addition the secondary parasitoids were, Alloxysta australiae (Ashmead), Dendrocerus carpenteri (Curtis), Chalcids sp.,and Aphidencyrtus sp. Data show that, Diaeretiella rapae was the most dominant and abundant primary parasitoid species represented 87.99% and 64.35% during 2011 and 2012 seasons, respectively. In spite of aphids, five aphid species namely, Schizaphis graminum (Rondani), Rhopalosiphum padi L., R. maidis (Fitch.), Sitobion avenae (Fab.) and Metopolophium dirhodum (Walker) were found attacking wheat plants in Assiut region. Rhopalosiphum padi and Schizaphis graminum were the most dominant and abundant cereal aphids on wheat plants represented (55.55 and 54.41%) and (40.68 and 43.11%) in both two species during 2011 and 2012 seasons, respectively. The maximum population level of cereal aphids was recorded during the 1st wk of March (529.0 and 729.0) during the two seasons, respectively. The parasitoids appeared early in the season in relatively low population density but its population fluctuated in high density during the 2nd wk of March (408.0 and 335.6) in 2011 and 2012 seasons, respectively, coincided with the collapse of aphids from wheat field. This work indicated that wheat fields are rich in aphid parasitoid species which of course play a significant role in suppressing aphid infestations.

Intraguild Predation between Lady Beetles and Lacewings: Outcomes and Consequences Vary with Focal Prey and Arena of Interaction

AbstractWe examined reciprocal intraguild predation (IGP) and cannibalism among various combinations of Coleomegilla maculata DeGeer and Chrysoperla cornea Stephens larvae as they developed feeding on greenbugs, Schizaphis graminum Rondani, on sorghum plants in microcosms. Pairs of C. maculata larvae suppressed aphids better than pairs of C. carnea larvae or heterospecific larval pairs and yielded the highest rate of plant survival. IGP by C. carnea larvae occurred mostly in the first instar, whereas C. maculata larvae were more aggressive in later instars. Although C. carnea was the superior intraguild predator, winning 62.7% of contests in microcosms, this value increased to 88.9% when the experiment was repeated in petri dishes without plant material, regardless of whether greenbugs or eggs of Ephestia kuehniella Zeller were offered as focal prey. Provision in petri dishes of the sessile, higher quality prey (Ephestia) as opposed to greenbugs, improved the survival of solitary larvae and delayed cannibalism and IGP until later developmental stages in both species. Larvae of C. maculata that cannibalized took longer to develop and weighed less at pupation, independent of the arena or prey offered. Although larvae of C. carnea did not pay a cost for cannibalism or IGP in microcosms, there were some negative developmental effects of IGP in petri dishes, particularly on the Ephestia diet. These results illustrate how the plant, as a substrate, can mediate the strength of IGP interactions and how the relative suitability of the focal prey can influence both the timing and consequences of cannibalism and IGP.

Mapping and candidate gene identification of loci determining tolerance to greenbug (Schizaphis graminum, Rondani) in barley

Greenbug is one of the most aggressive pests of barley and wheat. In Argentina, yield losses of wheat, barley, oat and sorghum crops caused by greenbug are chronic and at times severe. Since Marker Assisted selection for greenbug resistance genes in barley is very limited, the purpose of the current study was to map greenbug resistance genes in doubled haploid (DH) lines and to identify candidate genes. A set of DH lines of the Oregon-Wolfe Barley (OWB) mapping population derived from the cross between OWBDOM and OWBREC and both parental lines were screened for tolerance to greenbug. There was significant variation among the DH lines in foliar area (FA), dry weight (DW) and chlorophyll contents (Ch) between infested and control DH lines. Three main QTLs were identified. These QTLs explained 82 % of the FA, 80 % of DW and 58 % of Ch variability of infested plants. The initial and final FA and DW of controls and final DW of infested plants were associated with the same molecular markers on chromosome 2H (Vrs1, BmAc0144f, GBR259, GBS705). The final FA of infested plants was significantly linked to molecular markers on chromosome 5H (GBRO986, GBR518, GBM1483, GBR1082). The positive alleles were provided by OWBDOM. The content of chlorophyll of infested plants was associated with the marker loci Ris44, GBR1608, GBR1637N and GBS0785 on chromosome 7H, with the positive alleles provided by OWBREC. Both parents contributed to different tolerance traits. The QTLs found in this population are new greenbug resistance loci. A sequence homology search was performed to derive the putative function of the genes linked to the QTLs.

Biotype characterization and genetic diversity of the greenbug, Schizaphis graminum (Hemiptera: Aphididae), in north Tunisia

The greenbug Schizaphis graminum, is a major pest of wheat worldwide. Biotype screening of this pest is essential to develop pest management programs. In this research, eight greenbug clones, collected on wheat in the cereal-growing region of Béja (north Tunisia), were used to determine their damage on six reference wheat cultivars. All tested clones shared a unique biotypic profile, similar to biotype C. Moreover, DNA from the tested clones and that from seven reference clones of biotypes C, E, F, G, H, I and K, was analyzed, using 5 RAPD-PCR primers. The UPGMA method clustered samples into two distinct clades: a first one (I) included clones from north Tunisia, which were clearly associated to agricultural biotypes C, E, I and K, while a second clade (II) included non agricultural biotypes F, G and H. Results reported in this paper suggest that resistance genes Gb2, Gb3, Gb4, Gb5 and Gb6 in wheat would be the most efficient if used in wheat improvement programs for resistance against greenbug in Tunisia.

Establishment and Host Effects of Cereal Aphids on Switchgrass (Panicum virgatumL.) Cultivars1

Abstract. Potential for widespread plantings of switchgrass, Panicum virgatum L., as a biomass feedstock prompted its evaluation as a host for economically important cereal aphids. Seedlings of four cultivars of switchgrass, ‘Kanlow’, ‘BlackweN’, ’Cave-In-Rock’, and ’Sunburst’, were evaluated as hosts for greenbug, Schizaphis graminum (Rondani), biotypes E, I, and Florida; Russian wheat aphid, Diuraphis noxia (Kurdj.), biotype 2; bird-cherry oat aphid, Rhopalosiphum padi (L.); corn leaf aphid, R. maidis (Fitch); English grain aphid, Sitobion avenae (F.); and yellow sugarcane aphid, Sipha flava (Forbes). Greenbug biotype E and Russian wheat aphid biotype 2, both economically important cereal aphids in the United States, and English grain aphid were unable to establish on any of the switchgrass cultivars. However, greenbug biotypes I and Florida, bird-cherry oat aphid, corn leaf aphid, and yellow sugarcane aphid established on all cultivars tested. The aphids which successfully established on switchgrass al...

Registration of Eight Six‐Rowed Feed Barley Germplasm Lines Resistant to Both Russian Wheat Aphid and Greenbug

STARS 1006B (Reg. No. GP‐200, PI 659760), STARS 1007B (Reg. No. GP‐201, PI 659761), STARS 1008B (Reg. No. GP‐202, PI 659762), STARS 1009B (Reg. No. GP‐203, PI 659763), STARS 1010B (Reg. No. GP‐204, PI 659764), STARS 1011B (Reg. No. GP‐205, PI 659765), STARS 1012B (Reg. No. GP‐206, PI 659766), and STARS 1013B (Reg. No. GP‐207, PI 659767), are winter, six‐rowed, feed barley (Hordeum vulgare L.) germplasm lines developed cooperatively by the USDA‐ARS, in Stillwater, OK, and Aberdeen, ID as sources of resistance to Russian wheat aphid [RWA; Diuraphis noxia (Kurdjumov)] and greenbug [GB; Schizaphis graminum (Rondani)]. Each resistant line is in a ‘Post 90’ background and comparable with ‘Post 90’ (PI 549081) in yield, test weight, heading date, and height in the absence of RWA and GB. Each line is highly resistant to both RWA and GB and has a wide area of adaptation ranging from irrigated production in the northwestern United States to dryland production in the southern plains, where both RWA and GB can be problematic.

Long-term seasonal polymorphism of the Krasnodar greenbug population for virulence to sorghum varieties carrying different resistance genes

The genetic structure of the Krasnodar population of the greenbug (Schizaphis graminum Rondani) was analyzed in 2002 to 2010. A high level of general and seasonal polymorphism for the insect virulence to different sorghum accessions was revealed. Abiotic factors were shown to play an important role in the seasonal variation of the frequencies of virulence phenotypes: they can alter the relative competitiveness of greenbug clones, and, therefore, changes in environmental conditions lead to differential selection in the S. graminum population.

Investigation effect three diets on life table parameters Chrysoperla carnea (Steph.) (Neuroptera: Chrysopidae) under Laboratory Conditions

The common green lacewing, Chrysoperla carnea (Stephens) (Neuroptera: Chrysopidae) is best-known as biocontrol agent. The suitability diet was important in mass-rearing and releasing field. C.carnea has a serious role at IPM cultures apposite of aphid and whitefly pest. For this purpose, Schizaphis graminum (Rondani) (Hemiptera: Aphididae), Bemisia tabaci Gennadius (Hemiptera: Aleyrodidae) biotype-B 3 rd nymphs stage and Semi artificial diet as prey for Life table parameters was evaluated. All experiments were conducted at 25 ± 5 0 C, 60± 5% RH and photoperiod of 16:8 (L:D).This study, the collected data was analyzed by using Jack Knife model and SAS (9.1) soft ware and experimental design was formatted Completely Randomized Design (CRD) and comparison among means followed by Tukey’s HSD post hoc test. The highest Lx (number of individuals alive between age x and x+1) and the lowest dx (numbers dying during the age interval x) were 0.99 and 0.005 (%) that belonged semi artificial diet. Reproductive and stable population parameters such as Net Fertility rate, Net reproductive rate (R0), Gross reproductive rate (GRR), Intrinsic of increase (rm), Mean generation time (Tc) and Doubling time (DT) in aphid, whitefly and semi artificial diets were 244.9±4.1, 170.2±3.4, 364.6±2; 175.43±4.33, 156±5.4, 267±4.8; 0.143±0.005, 0.124±0.004, 0.185±0.002; 34.93±0.47, 38±0.74, 29.79±0.57 and 4.83±0.08, 5.58±0.06 and 3.74±0.05, respectively. According to these results, semi artificial diet was appropriate diet. Keyword: Chrysoperla carnea, life table parameters, Schizaphis graminum, Bemisia tabaci, Semi artificial diet.

THE INTEGRATIVE EFFECTS OF POPULATION DENSITY, PHOTOPERIOD, TEMPERATURE, AND HOST PLANT ON THE INDUCTION OF ALATE APHIDS INSCHIZAPHIS GRAMINUM

The wheat aphid Schizaphis graminum (Rondani) displays wing dimorphism with both winged and wingless adult morphs. The winged morph is an adaptive microevolutionary response to undesirable environmental conditions, including undesirable population density, photoperiod, temperature, and host plant. Here we studied the integrative effects of population density, photoperiod, temperature, and host plant on the induction of alate aphids in S. graminum. The present results show that these four factors all play roles in inducing alate aphids in S. graminum but population density is the most important under almost all circumstances. In importance, population density is followed by photoperiod, host plant, and temperature, in that order. These results indicate that ambient environmental factors are highly important to stimulation of alate aphids in S. graminum, especially when population density reaches 64 individuals per leaf.

Genome Organization, Phylogenies, Expression Patterns, and Three-Dimensional Protein Models of Two Acetylcholinesterase Genes from the Red Flour Beetle

Since the report of a paralogous acetylcholinesterase (AChE, EC3.1.1.7) gene in the greenbug (Schizaphis graminum) in 2002, two different AChE genes (Ace1 and Ace2) have been identified in each of at least 27 insect species. However, the gene models of Ace1 and Ace2, and their molecular properties have not yet been comprehensively analyzed in any insect species. In this study, we sequenced the full-length cDNAs, computationally predicted the corresponding three-dimensional protein models, and profiled developmental stage and tissue-specific expression patterns of two Ace genes from the red flour beetle (Tribolium castaneum; TcAce1 and TcAce2), a globally distributed major pest of stored grain products and an emerging model organism. TcAce1 and TcAce2 encode 648 and 604 amino acid residues, respectively, and have conserved motifs including a choline-binding site, a catalytic triad, and an acyl pocket. Phylogenetic analysis show that both TcAce genes are grouped into two insect Ace clusters and TcAce1 is completely diverged from TcAce2, suggesting that these two genes evolve from their corresponding Ace gene lineages in insect species. In addition, TcAce1 is located on chromosome 5, whereas TcAce2 is located on chromosome 2. Reverse transcription polymerase chain reaction (PCR) and quantitative real-time PCR analyses indicate that both genes are virtually transcribed in all the developmental stages and predominately expressed in the insect brain. Our computational analyses suggest that the TcAce1 protein is a robust acetylcholine (ACh) hydrolase and has susceptibility to sulfhydryl agents whereas the TcAce2 protein is not a catalytically efficient ACh hydrolase.

Biological and Serological Identification of Barley Yellow Dwarf Virus (BYDV) and Its Distribution in Iraq

Barley yellow dwarf virus (BYDV) was identified by means of symptoms on indicator plants, transmission by aphids, and serological characteristics. Symptoms of yellowing and stunting were appeared on leaf tips of Hordium vulgare, Triticum aestivum, and Avena fatua accompanied by stem stunting. Four species of aphids, Rhopalosiphum maidis, R. padi, Macrosiphum avenae, and Schizaphis graminum were found vectoring the virus. Extracts from wheat and barley plants showing yellowing and stunting were reacted positively with polyclonal anti-BYDV antiserum in DAS-ELISA. Most of samples that gave positive reactions by ELISA gave positive reactions with tissue blot immunoassay (TBIA). Higher incidence of BYDV was found in the northern parts of Iraq. Several economical and weed plants, collected from wheat and barley fields and vicinity sites have been found to harbor the virus. These hosts may acts as virus reservoir transmitting to wheat and barley plants by aphids.

Effect of Diets on Biology ofAbaris basistriataandSelenophorus seriatoporus(Coleoptera: Carabidae)

AbstractGround beetles or carabids are collective terms for the beetle family Carabidae. This family contains many species considered important predators associated with agricultural crops. The current study aimed to evaluate the effect of different diet types on consumption, fecundity, and egg viability of Abaris basistriata Chaudoir and Selenophorus seriatoporus Putzeys (Coleoptera: Carabidae) . The diets assessed were as follows: larvae of Tenebrio molitor L.; minced beef; dry cat food; the greenbug, Schizaphis graminum (Rondani); seeds of signal grass, Brachiaria decumbens Stapf; and a diet mixture. Five males and five females of each species were kept isolated in a plastic container divided by a silicon barrier, one side being filled with sifted soil that was moistened for oviposition and the other lined with filter paper to receive the diet. A. basistriata did not consume the B. decumbens seeds. The most consumed diet by A. basistriata and S. seriatoporus adults was T. molitor larvae. S. graminum and T. molitor larvae and diet mixture were considered the diets most favorable for the reproductive capacity of A. basistriata and S. seriatoporus, respectively. However, T. molitor larvae and diet mixture were the most favorable diets for rearing both carabid species in the laboratory.

Registration of Twelve Sorghum Germplasm Lines Tolerant to Greenbug Feeding Damage

The biotypic diversity of the greenbug [Schizaphis graminum (Rondani)] and development of lines with tolerance to greenbug feeding are ongoing concerns of sorghum [Sorghum bicolor (L.) Moench.] breeding programs in the United States. The genetic male sterile population KP7B and four germplasm sources (IS 25246, IS 27002, IS 27834, and IS 27903) were used in population improvement for tolerance to greenbug feeding. Differences in tolerance were quantified by estimating the chlorophyll content of leaf tissues using a SPAD chlorophyll meter following a 7‐d period of greenbug feeding on leaves. Twelve sorghum germplasm lines KS 121 (Reg. No. GP‐718, PI 651584), KS 122 (Reg. No. GP‐719, PI 651585), KS 123 (Reg. No. GP‐720, PI 651586); KS 124 (Reg. No. GP‐721, PI 651587), KS 125 (Reg. No. GP‐722, PI 651588), KS 126 (Reg. No. GP‐723, PI 651589), KS 127 (Reg. No. GP‐724, PI 651590), KS 128 (Reg. No. GP‐725, PI 651591), KS 129(Reg. No. GP‐726, PI 651592), KS 130 (Reg. No. GP‐727, PI 651593), KS 131 (Reg. No. GP‐728, PI 651594), and KS 132 (Reg. No. GP‐729, PI 651595) with enhanced tolerance to greenbug feeding were developed and released by the Kansas Agricultural Experiment Station in October 2007. These lines are three‐dwarf (dw1, Dw2, dw3, dw4) in height, photoperiod‐insensitive, and possess unique combinations of plant color and tolerance to damage by greenbug biotypes E, I, and K. All 12 lines restore fertility in the A1 cytoplasm system and hence can be used as R‐lines in breeding programs to develop new hybrids with greenbug feeding tolerance.

A Genomic Reappraisal of Symbiotic Function in the Aphid/Buchnera Symbiosis: Reduced Transporter Sets and Variable Membrane Organisations

Buchnera aphidicola is an obligate symbiotic bacterium that sustains the physiology of aphids by complementing their exclusive phloem sap diet. In this study, we reappraised the transport function of different Buchnera strains, from the aphids Acyrthosiphon pisum, Schizaphis graminum, Baizongia pistaciae and Cinara cedri, using the re-annotation of their transmembrane proteins coupled with an exploration of their metabolic networks. Although metabolic analyses revealed high interdependencies between the host and the bacteria, we demonstrate here that transport in Buchnera is assured by low transporter diversity, when compared to free-living bacteria, being mostly based on a few general transporters, some of which probably have lost their substrate specificity. Moreover, in the four strains studied, an astonishing lack of inner-membrane importers was observed. In Buchnera, the transport function has been shaped by the distinct selective constraints occurring in the Aphididae lineages. Buchnera from A. pisum and S. graminum have a three-membraned system and similar sets of transporters corresponding to most compound classes. Transmission electronic microscopic observations and confocal microscopic analysis of intracellular pH fields revealed that Buchnera does not show any of the typical structures and properties observed in integrated organelles. Buchnera from B. pistaciae seem to possess a unique double membrane system and has, accordingly, lost all of its outer-membrane integral proteins. Lastly, Buchnera from C. cedri revealed an extremely poor repertoire of transporters, with almost no ATP-driven active transport left, despite the clear persistence of the ancestral three-membraned system.

Fine genetic mapping of greenbug aphid-resistance gene Gb3 in Aegilops tauschii

The greenbug, Schizaphis graminum (Rondani), is an important aphid pest of small grain crops especially wheat (Triticum aestivum L., 2n = 6x = 42, genomes AABBDD) in many parts of the world. The greenbug-resistance gene Gb3 originated from Aegilops tauschii Coss. (2n = 2x = 14, genome D(t)D(t)) has shown consistent and durable resistance against prevailing greenbug biotypes in wheat fields. We previously mapped Gb3 in a recombination-rich, telomeric bin of wheat chromosome arm 7DL. In this study, high-resolution genetic mapping was carried out using an F(2:3) segregating population derived from two Ae. tauschii accessions, the resistant PI 268210 (original donor of Gb3 in the hexaploid wheat germplasm line 'Largo') and susceptible AL8/78. Molecular markers were developed by exploring bin-mapped wheat RFLPs, SSRs, ESTs and the Ae. tauschii physical map (BAC contigs). Wheat EST and Ae. tauschii BAC end sequences located in the deletion bin 7DL3-0.82-1.00 were used to design STS (sequence tagged site) or CAPS (Cleaved Amplified Polymorphic Sequence) markers. Forty-five PCR-based markers were developed and mapped to the chromosomal region spanning the Gb3 locus. The greenbug-resistance gene Gb3 now was delimited in an interval of 1.1 cM by two molecular markers (HI067J6-R and HI009B3-R). This localized high-resolution genetic map with markers closely linked to Gb3 lays a solid foundation for map based cloning of Gb3 and marker-assisted selection of this gene in wheat breeding.

Host Race Evolution inSchizaphis graminum(Hemiptera: Aphididae): Nuclear Dna Sequences

The greenbug aphid, Schizaphis graminum (Rondani) was introduced into the United States in the late 1880s, and quickly was established as a pest of wheat, oat, and barley. Sorghum was also a host, but it was not until 1968 that greenbug became a serious pest of it as well. The most effective control method is the planting of resistant varieties; however, the occurrence of greenbug biotypes has hampered the development and use of plant resistance as a management technique. Until the 1990s, the evolutionary status of greenbug biotypes was obscure. Four mtDNA cytochrome oxidase subunit I (COI) haplotypes were previously identified, suggesting that S. graminum sensu lato was comprised of host-adapted races. To elucidate the current evolutionary and taxonomic status of the greenbug and its biotypes, two nuclear genes and introns were sequenced; cytochrome c (CytC) and elongation factor 1-α (EF1-α). Phylogenetic analysis of CytC sequences were in complete agreement with COI sequences and demonstrated three distinct evolutionary lineages in S. graminum. EF1-α DNA sequences were in partial agreement with COI and CytC sequences, and demonstrated two distinct evolutionary lineages. Host-adapted races in greenbug are sympatric and appear reproductively isolated. Agricultural biotypes in S. graminum likely arose by genetic recombination via meiosis during sexual reproduction within host-races. The 1968 greenbug outbreak on sorghum was the result of the introduction of a host race adapted to sorghum, and not selection by host resistance genes in crops.

Insecticidal effects of Ungernia severtzovii bulb extracts against the grain aphid Schizaphis graminum (Rondani)

Insecticidal effect of Ungernia severtzovii bulbs extract has been investigated against the grain aphid Schizaphis graminum. LC50 value of the ethanolic extract of U. severtzovii against the female aphids was 0.235% (2.35g/l). There was 100% mortality of the subsequent nymphs of the treated females at 0.25–1.0%. The extract was equally active against the nymphs at the highest concentrations. Hexane and ethanolic extracts were the most active against the aphids of all the extracts. Fractionation of the hexane extract by TLC yielded three fractions. Fraction II was the most active (>90% mortality) against the aphids. Xanthoxylin was identified as the major constituent in fraction II of the hexane extract and may be responsible for the insecticidal effect of U. severtzovii.

Species Composition of Aphid Vectors (Hemiptera: Aphididae) of Barley Yellow Dwarf Virus and Cereal Yellow Dwarf Virus in Alabama and Western Florida

Yellow dwarf is a major disease problem of wheat, Triticum aestivum L., in Alabama and is estimated to cause yield loss of 21-42 bu/acre. The disease is caused by a complex of viruses comprising several virus species, including Barley yellow dwarf virus-PAV and Cereal yellow dwarf virus-RPV. Several other strains have not yet been classified into a specific species. The viruses are transmitted exclusively by aphids (Hemiptera:Aphididae). Between the 2005 and 2008 winter wheat seasons, aphids were surveyed in the beginning of each planting season in several wheat plots in Alabama and western Florida Collected aphids were identified and bioassayed for their yellow dwarf virus infectivity. This survey program was designed to identify the aphid species that serve as fall vectors of yellow dwarf virus into winter wheat plantings. From 2005 to 2008, bird cherry-oat aphid, Rhopalosiphum padi (L.); rice root aphid, Rhopalosiphum rufiabdominale (Sasaki); and greenbug, Schizaphis graminum (Rondani), were found consistently between October and December. The species of aphids and their timing of appearance in wheat plots were consistent with flight data collected in North Alabama between 1996 and 1999. Both R. padi and R. rufiabdominale were found to carry and transmit Barley yellow dwarf virus-PAV and Cereal yellow dwarf virus-RPV. The number of collected aphids and proportion of viruliferous aphids were low. Although this study has shown that both aphids are involved with introduction of yellow dwarf virus to winter wheat in Alabama and western Florida, no conclusions can be made as to which species may be the most important vector of yellow dwarf virus in the region.

Infectivity of Steinernema mushtaqi (Rhabditida: Steinernematidae) against insect pests and their mass production

The infectivity of entomopathogenic nematode (EPN), Steinernema mushtaqi was tested against legume pod borer, Maruca vitrata, tobacco caterpillar, Spodoptera litura, blue butterfly, Lampides boeticus, red hairy caterpillar, Amsacta moorei, brown bug, Clavigralla gibbosa, mealy bug, Centrococcus somatics, fruit borer, Earias vittella and green bug, Nezara viridula larvae and in vivo mass production of the above-tested species of EPN have been carried out during 2008. S. mushtaqi was found to be more pathogenic to A. moorei, as it brought about 100% mortality within 48 h, than to S. litura, L. boeticus, N. viriduala and E. vittella, as mortality occurred within 72 h; whereas this level of mortality was recorded in C. somatis, C. gibbosa and M. vitrata within 144 h. No mortality was observed in the control treatment. Multiplication of S. mushtaqi and the yield of infective juveniles (IJs) on these insects was the highest (0.94 × 105 IJs/cadaver) from N. viriduala, followed by S. litura (0.76 × 105 IJs/cadaver), L. boeticus as also C. gibbosa (0.31 × 105 IJs/cadaver) and M. vitrata (0.20 × 105 IJs/cadaver). Very poor populations of IJs were found from A. moorei (0.15 × 105 IJs/cadaver) and C. somatics (0.01 × 105 IJs/cadaver). No multiplication of IJs was found from the cadaver of E. vittella. This opens a new hope of utilising S. mushtaqi in the insect pests management programme.