Control Of Russian Wheat Aphid Research Articles

Endophytic Effect of the South African Beauveria bassiana Strain PPRI 7598 on the Population Growth and Development of the Russian Wheat Aphid, Diuraphis noxia

The Russian wheat aphid (RWA), Diuraphis noxia (Kurdjumov), is one of the main pests of small-grain cereal crops, including bread wheat, Triticum aestivum (Poaceae). In a series of glasshouse experiments, we evaluated the systemic effect of endophytic Beauveria bassiana strain PPRI 7598 on D. noxia biotype RWASA1 using three South African wheat cultivars, Gariep, Molopo, and Kariega. The objectives of the study were: (a) to determine the effect of endophytism on RWA reproduction and population growth, and (b) to assess the effect of the endophyte on aphid biomass and T. aestivum response to D. noxia herbivory using a damage rating index. Plant endophytic colonisation was confirmed before each trial using a B. bassiana-selective medium. Three independent trials were performed 10 days apart under glasshouse conditions. The effect of the endophyte-treated versus non-treated plants varied significantly in terms of net reproductive rate (R0) and the intrinsic rate of increase (rm) of the D. noxia population. Overall, the endophyte significantly reduced D. noxia R0 by approximately 14 nymphs/female and decreased the aphid mass by 13% in treated plants, whereas the mean aphid mass increased by 17% in control plants in all pooled cultivars. These findings demonstrated the endophytic potential of B. bassiana strain PPRI 7598 for suppression of D. noxia populations in RWASA1-susceptible cultivars. The integration of B. bassiana endophytism with host plant resistance may counteract biotype development and support a more sustainable approach towards RWA control in integrated pest management programmes.

Nitric oxide is an upstream signal involved in the multisignalling network during the Russian wheat aphid resistance response and its application enhances resistance

The Russian wheat aphid (RWA) is serious pest of wheat in South Africa since its discovery in 1978. Nitric oxide (NO) plays an essential role in the RWA resistance response of wheat. This study was conducted to establish whether NO acts upstream or downstream of salicylic acid (SA) during the RWA defence response and also to investigate the effect of NO application on RWA control. In addition, the involvement of peroxynitrite in the RWA resistance response of wheat was studied. Resistant and/or susceptible plants grown under controlled conditions (25 ± 2°C) were used. Using a NO donor, sodium nitroprusside (SNP), and a NO production inhibitor, sodium tungstate (NaWO4), it was proved that NO acts upstream of SA during the RWA resistance response of wheat. Furthermore, a significant decrease in RWA intrinsic increase rate (rm) and disease symptom development after SNP application emphasized the role of NO in the RWA resistance responses. High levels of peroxynitrite (by-product of NO) content in the RWA infested resistant plants and inhibition of secondary defence enzymes (β-1,3-glucanase and peroxidase) after urate (inhibitor of peroxynitrite production) application proposed the involvement of this molecule in the signalling events of the RWA resistance.

Mapping resistance genes conferring tolerance to RWA (Diuraphis noxia) in barley (Hordeum vulgare)

The Russian wheat aphid (RWA) is one of the most aggressive pests of barley and wheat. The outbreak of RWA occurred in Argentina in 2008 caused serious damage to barley cultivars. The most effective and sustainable method of RWA control is to identify new resistance genes. The purpose of the current research was to map RWA resistance genes in a set of double haploid (DH) lines of the Oregon-Wolfe Barley (OWB) mapping population derived from the cross between OWBDOM and OWBREC. The DH and both parental lines were screened for antixenosis, tolerance and antibiosis to RWA. There was significant variation among the DH lines in most of the traits studied. However, only tolerance resulted in significant quantitative trait loci (QTLs) associated with the molecular markers. Two main QTLs were identified. These explained 90 and 79 % of the variability of foliar area and chlorophyll content, respectively, of infested and control plants. The initial and final foliar area and the variation in foliar area were associated with the same molecular markers on chromosome 2H (BmAc0125, Vrs1, BmAc0144f and BmAg0113e). The positive alleles were provided by OWBDOM. The content of chlorophyll was associated with the marker loci WMC1E8, MWG912, ABC261, MWG2028 and Blp on chromosome 1H, with the positive alleles provided by OWBREC. Both parents contributed to different tolerance traits, with foliar area and chlorophyll content remaining as the plant traits most affected by aphid feeding. The QTLs found in this population are new RWA resistance loci. A sequence homology search was performed to derive the putative function of the genes linked to the QTLs.

Comparison of development and demographic parameters of Diuraphis noxia (Hem., Aphididae) and its parasitoid, Diaeretiella rapae (Hym., Braconidae: Aphidiinae)

Demographic parameters of Diuraphis noxia (Mordvilko) and its parasitoid, Diaeretiella rapae (McIntosh) were investigated under laboratory conditions at temperatures of 20 ± 1°C, 60 ± 5% relative humidity of 60 ± 5% and a photoperiod of 16: 8 (light: dark) hours. The survival rates (lx ) and the life expectancy (ex ) at the beginning of adult emergence were 86% and 25.81 days for D. noxia and 100% and 7.36 days for D. rapae, respectively. Based on the Weibull distribution parameters, the survival curves were type I for both D. noxia and D. rapae, which indicates that mortality mostly occurred in older stages. The r m-values in aphid and parasitoid were obtained as 0.22 ± 0.002 and 0.19 ± 0.003 day−1, respectively. Mean generation time (T) and doubling time (DT) were 15.93 ± 0.202 and 3.15 ± 0.031 days for the aphid and 15.33 ± 0.071 and 3.67 ± 0.054 days for the parasitoid, respectively. The R0 -values of D. noxia and D. rapae were evaluated 33.19 ± 0.961 and 18.07 ± 0.761 females/female/generation, respectively. The gross and net fecundity rates were 59.21 ± 1.94 and 32.825 ± 0.972 nymphs/female/day for the aphid and 37.59 ± 1.46, and 33.8 ± 1.51 eggs/female/day for the parasitoid, respectively. The results of this research indicated that D. rapae is an adequate parasitoid for control of Russian wheat aphid.

Molecular Mapping and Allelic Relationships of Russian Wheat Aphid–Resistance Genes

The Russian wheat aphid (RWA), Diuraphis noxia (Mordvilko), is a serious economic pest of wheat (Triticum aestivum L.) worldwide. Although resistant wheat cultivars provide good control of RWA, genetic characterization is critical to the continual use of aphid‐resistance genes. The objective of this study was to determine the chromosome location and the genetic relationships of the RWA‐resistance genes Dn1, Dn2, Dn4, Dn5, Dn6, Dnx, and several uncharacterized Dn genes. Molecular mapping demonstrated that Dn genes in four uncharacterized wheat lines (PI 47545, PI 222666, PI 222668, and PI 225245) as well as Dn1, Dn2, Dn5, Dn6, and Dnx are tightly linked to microsatellite markers Xgwm44 and Xgwm111 Deletion bin mapping assigned Xgwm44 physically in the region distal to the breakpoints 7DS‐4 (FL 0.61) and Xgwm111 distal to 7DS‐5 (FL 0.36) of wheat chromosome arm 7DS. Allelism tests detected no segregation for susceptibility among TC1F1 plants from the test crosses or among F2 plants derived from intercrosses between wheat lines containing each of these known Dn genes. Both marker‐linkage analyses and allelism tests revealed that all these Dn genes are clustered in a region linked to Xgwm111 and are either alleles of a single locus or are closely related members of a Dn gene family. Dn4 and the uncharacterized Dn gene in PI 151918 are either allelic or linked on wheat chromosome 1DS. The linked markers and genetic relationships of these Dn genes will greatly facilitate their use in wheat breeding and the deployment of aphid‐resistant cultivars.

Efficacy of Beauveria bassiana (Hyphomycetes) for control of Russian wheat aphid (Homoptera: Aphididae) on resistant wheat under field conditions

The Russian wheat aphid, Diuraphis noxia (Kurdjumov) (Homoptera: Aphididae) is considered the most important pest of wheat produced under dryland field conditions in South Africa. As part of an integrated pest management strategy, the entomopathogenic hyphomycete Beauveria bassiana (Balsamo) Vuillemin was evaluated in combination with antibiotic host plant resistance under dryland field conditions during 1998 and 1999. A commercial formulation, Mycotrol® ES, was applied at a rate of 2.4 L (5×1013 conidia) per hectare +0.1% organosilicone surfactant. During both years, two applications were administered, i.e., on growth stages 31 (first node detectable) and 39 (early flag leaf). An additional treatment, application at growth stage 39 only, was included during 1999. Over the duration of the 1998 trial, ca. 65% fewer aphids were observed on treated plots compared with controls. A similar level of population reduction was observed during the 1999 trial; however, treatment effects were only briefly evident due to a rapid field-wide decline in aphid populations caused by adverse (cool, wet) weather conditions. The early application (GS 31) resulted in some level of control only during 1998. It was hypothesized that this phenomenon was the result of greater exposure to the spray applications and/or greater secondary pick-up of fungal inoculum by the aphids due to the higher level of aphid activity observed on the cultivar employed during that year. In this regard, migration of D. noxia onto the flag leaves should be further investigated as a behavioural trait for possible exploitation when considering the use of a mycoinsecticide.

Search for, and release of, parasitoids for the biological control of Russian wheat aphid in Washington State (USA)

Parasitoids of Russian wheat aphid, Diuraphis noxia (Kurdjumov), from Morocco, and the Middle East were imported, reared, and mass produced for classical biological control use in Washington State. In total, more than 200 000 parasitoids were released over 53 sites from 1988 to 1992. Some species have established, but the long term effect of the program has yet to be documented.

Effect of Russian Wheat Aphid on Wheat Root and Shoot Development in Resistant and Susceptible Genotypes

Genetic resistance is an important management component in the control of Russian wheat aphid (Diuraphis noxia Mordvilko) (RWA). The range of leaf symptoms associated with several resistance sources indicate that differences may occur in seedling development. This study was conducted to determine differences in wheat (Triticum aestivum L.) seedling shoot and root development among resistant and susceptible wheat genotypes infested with RWA. The effectiveness of one resistance source identified in greenhouse seedlings was characterized in field‐grown F2 plants. Visual damage and leaf and root development were measured for 17 lines in the greenhouse. Dry weight, grain yield, and harvest index were studied in infested and noninfested, field‐grown F2 populations generated from ‘Moro’/PI294994 and ‘Hyak’/PI294994. PI48650 and PI294994 had superior seedling shoot and nodal root system development when compared to susceptible genotypes. Visual evaluations were effective in separating susceptible genotypes from potential resistance sources; however, leaf symptoms were not effective in characterizing the most promising RWA resistance resources. Root measurements in conjunction with leaf symptoms identified seedling genotypes least affected by RWA. Russian wheat aphid resistant adult plants produced significantly more dry weight and grain yield and a greater harvest index than susceptible plants in the two populations. Trends for these characteristics were similar for resistant plants in the infested population and plants in the noninfested population.

Russian Wheat Aphid Control Using Seed and Rescue Treatments, 1993

Abstract Winter wheat was planted (8 Sep) at a rate of 75 lb per acre in a Lismore silty clay loam soil in 17.5-cm rows using a 10-row International drill near the Northern Grain Insects Research Laboratory, Brookings, SD. The experiment was arranged in CRBD with 4 replications. Treatments were randomly assigned to 1-m2 plots of winter wheat. Individual treatment plots were artificially infested (2 Oct) with laboratory-reared RWA. Pretreatment counts (6 Oct) indicated 25.8 RWA/tiller were present. Foliar rescue applications were carried out (9 Oct) using a hand-held spray boom equipped with 6 TeeJet 8002 nozzles spaced 12 inches apart that delivered 20 gpa at 25 psi while travelling at 3 mph. Miles, Inc. provided the material for seed treatments (Gaucho 480 FS), which was applied 2 wk prior to planting time for comparison with foliar-applied rescue treatments. The 5 DAT (14 Oct) RWA census was performed by randomly selecting 4 tillers from each quadrant and one from the center of each 1-m2 plot. Additionally, a 23 DAT count (1 Nov) was conducted in the same manner to determine residual RWA control. Aphid count data were subjected to SAS’s General Linear Models (GLM) procedure and means were compared using Duncan’s Multiple Range Test

Reduced Rates of Foliar Insecticides for Control of Russian Wheat Aphid (Homoptera: Aphididae) in Western Canada

Field and greenhouse experiments were conducted to evaluate reduced rates of foliar insecticides for control of Russian wheat aphid, Diuraphis noxia (Mordvilko), on wheat, Triticum aestivum. L. In an initial field experiment on winter wheat, chlorpyrifos at 400 g (AI)/ha was the best treatment, achieving 100% control after 14 d. Subsequent greenhouse experiments indicated that, for chlorpyrifos applied to two-leaf plants using a cabinet sprayer, the rate could be reduced to 100 g (AI)/ha with 91–95% control after 7 d. The toxic action of chlorpyrifos against the aphids was rapid, with 33% control 2 h after spraying. When surviving aphids were removed from treated plants 2 h, 1 d, or 2 dafter spraying and incubated on untreated wheat, no further mortality occurred. Apparently, the Russian wheat aphid must receive prolonged exposure to the 0- to 2-d chlorpyrifos residues for adequate (>90%) control to occur. Chlorpyrifos applied to three-leaf wheat at 125 g (AI)/ha did not provide residual protection against Russian wheat aphid infesting treated plants 2, 4, and 7 d after spraying. Residue analysis showed that chlorpyrifos residues declined rapidly on the treated plants with a half-life of ≈1 d. Also, by 2 d after spraying, 90% of the residues had been absorbed into the leaves and may not have been available to the infesting aphids. When field applications using a bicycle sprayer were compared directly with cabinet-sprayer applications, better control (93–97% versus 80–83%) was achieved with field applications. In a subsequent aerially applied experiment to field-test reduced rates of chlorpyrifos, 240 g (AI)/ha gave 99% control of Russian wheat aphid on winter wheat after 14 d. We concluded that the recommended rate of chlorpyrifos for control of Russian wheat aphid in western Canada could be reduced from 480 to 240 g (AI)/ha.

Compatibility of Imidacloprid with Fungicides as a Seed-Treatment Control of Russian Wheat Aphid (Homoptera: Aphididae) and Effect on Germination, Growth, and Yield of Wheat and Barley

Imidacloprid insecticide, applied as a seed treatment, singly or in combination with fungicides (carboxin-thiram, triadimenol-captan, and tebuconazole-thiram), protected growing plants of wheat and barley from developing infestations of Russian wheat aphid, Diuraphis noxia (Mordvilko) for 27-85 d after planting based on four greenhouse and four field trials. There were no compatibility problems in insecticide performance by combining imidacloprid with fungicides on the seed. Imidacloprid significantly reduced plant damage by D. noxia in all trials and increased yields in three of three field trials where plots were entirely infested. As a seed treatment, imidacloprid offers an environmentally safer approach to the control of D. noxia than is possible with wide-spectrum aerial or in-furrow granular insecticide treatments.

Control of Russian Wheat Aphid (RWA) in Winter Wheat, 1989:

Abstract Seventeen insecticides in a total of 26 combinations were evaluated for performance in controlling RWA in a lightly infested field near Connell, Franklin County, WA. Treatments were applied with a CO2-powered backpack sprayer with a 9 ft boom calibrated to deliver 20 gal/acre at 30 psi. The insecticides were applied on 19 Oct (treatments 1-12) and 20 Oct (treatments 13-28) because wind increased to > 5 mph before spraying could be completed. Plots were 18 x 18 ft, replicated 4 times, and arranged in a completely RCB design. The plots were located within a block of wheat seeded on 27 Aug (seeding rate: 42 lb/acre, 18 inch row spacings). Pretreatment wheat seedlings averaged 3 tillers and main stems. Treatments were evaluated at 7 and 14 DAT. Approximately 7 plants with symptomatic tillers were taken from each plot, placed into paper bags and held in a cooler until they were placed in Berlese-Tulgren funnels later in the day. After extraction, the number of plants and tillers for each sample was recorded; aphid densities for this evaluation are expressed as number of aphids per tiller. RWA comprised 96% of the aphid species while the remaining 4% were bird cherry-oat aphids. Results were thus analyzed on the basis of the total number of aphids extracted per treatment.

Control of Russian Wheat Aphid Using a Systemic Seed Treatment, 1992:

Abstract Different rates of the systemic seed treatment, NTN 33893, were evaluated for RWA control in winter wheat. Treated seed was planted in strip plots, measuring 8 ft by 50 ft on 1 Sep at the MSU-Central Agricultural Research Center, Moccasin, MT. Numbers of RWA were recorded on each of 10 plants randomly selected from 3 locations in each treated and untreated plot. Data were analyzed by analysis of variance and treatment means separated using LSD.

Control of Russian Wheat Aphid on Winter Wheat, 1989:

Abstract Twelve insecticides in a total of 15 formulations were evaluated as controls against the RWA in a heavily infested field near Davenport, Lincoln County, WA. Treatments were applied on 15 Nov with a CO2-powered backpack sprayer with a 9 ft boom calibrated to deliver 20 gal/acre at 30 psi. At treatment, all of the plants had from 2-5 tillers. Plots were 18 x 18 ft, each separated by an 18 ft buffer row, and replicated 4 times in a RCB design. These plots were located within a block of wheat seeded on 20 Sep (seeding rate: 98 lb/acre, 10 inch row spacing). At least 10 plants and over 50 total tillers were taken at random from each plot, placed into paper bags, and transported back to the lab in coolers. Aphids were recovered from samples using Berlese-Tulgren funnels. The number of plants and tillers for each sample was recorded. Aphid population densities for this evaluation are expressed as numbers of aphids per tiller. RWA represented 98% of the aphid species present; most of the remaining 5% were bird cherry-oat aphid. This proportion was not changed by the insecticide treatments.

Evaluation of Foliar Treatments for Russian Wheat Aphid Control, 1992:

Abstract Selected insecticides were evaluated with and without a surfactant for efficacy against RWA in a winter wheat field seeded 26 Aug 1991 in Judith Basin County, Montana. Insecticide treatments were applied on 26 Sep at the 4-5 leaf growth stage. Rll, a non-ionic surfactant, was added at 0.25% v/v. Treatments were applied using a CO2-powered backpack sprayer equipped with a 10 ft hand held spray boom and Teejet 8001LP flat-fan nozzles. The sprayer was calibrated to deliver 10.5 gal/acre at 20 psi. Treatments were arranged in a RCB design with 3 replicates, each measuring 20 x 30 ft. Insecticide efficacy was assessed by clipping 10 tillers from each treated and untreated replicate and counting the number of RWA on each tiller. Data were analyzed by analysis of variance and treatment means separated using LSD.

Russian Wheat Aphid Control in Winter Wheat, 1990

Abstract Insecticide applications applied in combination and singly were evaluated for performance against RWA in a winter wheat field seeded Sep 89 in Carbon County, Mont. Insecticide treatments were applied using a CO2-powered backpack sprayer equipped with a 10 ft hand held spray boom and Teejet 8001LP flat-fan nozzles. The sprayer was calibrated to deliver 10.5 gal/acre at 20 psi. Chemical applications were applied on 3 May at first joint growth stage. Treatments were arranged in a randomized complete block design with 3 replicates, each measuring 20 × 30 ft. Insecticide efficacy was assessed by clipping 10 tillers from each treated and untreated replicate and counting the number of RWA on each tiller. Plots were machine harvested using a Hege 125C plot combine with a 4-ft header. One section, measuring 20 × 4 ft, was harvested from each replicate. Grain samples were cleaned and yield calculated.

Control of Russian Wheat Aphid on Spring Wheat, 1989

Abstract Sixteen insecticides were evaluated for performance in controlling RWA. These were applied 6 Jun to spring wheat (growth stage: anthesis to early milk) grown on the USDA/Washington State Univ., Western Regional Plant Introduction Station, Central Ferry, WA. Treatments were applied with a hand-held CO2 sprayer calibrated to deliver 17 gpa at 30 psi. Plots were 10 × 20 ft, replicated 4 times in a randomized complete block design. The plots were established within a block of wheat seeded on 1 Apr (seeding rate: 60 lb/acre). Treatments were evaluated at 5 and 14 DAT, based on aphids/tiller (5 tillers/plot, with sampling directed at tillers exhibiting RWA-induced symptoms, i.e. streaked and rolled leaf sheaths and leaves). Aphids were recovered from samples using Berleze-Fulgren funnels.

Control of Russian Wheat Aphid and Bird Cherry-Oat Aphid on Winter Wheat in the Fall, 1988

Abstract Twelve insecticides were evaluated for performance in controlling the named grain aphids, with applications made 4 Oct to soft white winter wheat (growth stage: 2-5 tiller) grown on the Washington State Univ., Irr. Agric. Res. & Ext. Center, Roza Farm, Prosser, WA. Treatments were applied using a CO2 plot sprayer (8001 nozzles with 100 mesh screen) mounted on a bicycle-wheeled carriage. Sprayer output was 19 gal/acre at 30 psi. Plots were 4 × 15 ft (4 rows on 12 inch row spacing), replicated 5 times in a randomized complete block design. Plots were planted 2 Sep (seeding rate: 45 lb/acre). Treatments were evaluated at 3, 8, and 17 DAT, based on aphids/tiller (20 tillers/plot) sampled at random, field-bagged, and subsequently transferred to a Berlese funnel to extract the aphids. Plots were harvested on 10-11 Aug using a Hege combine.

Control of Russian Wheat Aphid, 1988

Abstract This evaluation was conducted in a winter wheat field in Big Horn County approximately 25 miles south of Billings, Mont. The field was seeded September 1987. Insecticide treatments were applied using a CO2-powered backpack sprayer equipped with a 10-ft hand-held spray boom and Teejet 8001LP flat-fan nozzles. The sprayer was calibrated to deliver 10.5 gal water/acre at 20 psi. Treatments were applied on 13 May when the flag leaf of the wheat plants was just visible and arranged in a randomized complete block design with 3 replicates, each measuring 20 by 30 ft. Insecticide efficacy was assessed by clipping 30 tillers from each treated and untreated replicate and counting the number of RWA on each tiller. Plots were machine harvested using a small-plot combine equipped with a 3-ft header. Two sections, measuring 28 by 3 ft, were harvested from each replicate. Grain samples were cleaned with yield calculated and test weight measured.

Control of Russian Wheat Aphid, 1988

Abstract A small-plot field test was conducted in a continuous dryland wheat field near Hugoton, Kans., to determine the relative effectiveness of 7 insecticides against RWA. Plots were 5.5 by 7.6 m, arranged in a randomized complete block design, and replicated 3 times. Chemical applications were made 13 Apr with a CO2-pressurized backpack hand sprayer calibrated to deliver 119.7 liters/ha at 138 kilopascals using 4 Spraying Systems X-6 (tip size) nozzles. Wheat plants were in the early jointing stage of development at time of application. RWA populations were sampled by randomly selecting 20 stems/plot and cutting them off at ground level with scissors. Stems were placed in plastic bags and transported to the laboratory, where aphids were extracted using Berlese funnels. Treatment efficacy was evaluated at 2, 7, 15, 21, and 33 DAT. Grain yields were determined by hand harvesting and machine threshing 9.8 m of row/plot.