Macrosiphum Avenae Research Articles

Analysis of the count of populations and harmfulness of phytophages of agrocenoses of grain cereals of the Central ForestSteppe of Ukraine

The count of harmful entomofauna, damage to plants by phytophages and the proportion of their colonization of soft wheat (winter and spring) and common barley (spring) in the Central Forest-Steppe of Ukraine in the spring-summer period of 2004–2019 were analyzed. Such specialized pests as: leafhoppers (Macrosteles laevis Ribaut, Psammotettix alienus L., Calligypona striatella Fall.), aphids (Schizaphis graminum (Rondani), Macrosiphum (Sitobion) avenae (F.), Brachycolus (Cuernavaca) noxius Mordv., Rhopalosiphum padi (L.)), grain bugs (Eurygaster integriceps Put., Eurygaster maura L., Eurygaster austriaca Schrank, Aelia acuminata L.), wheat trips (Haplothrips tritici Kurd.), common ground beetle (Zabrus tenebrioides Goeze), аnisoplia austriaca beetle (Anisoplia austriaca Herbst, Anisoplia segetum Herbst), grain flea beetles (Phyllotreta vittula Redt., Chaetocnema hortensis Geoffr., Chaetocnema aridula Gyll.), cereal leaf beetle (Oulema melanopus (L.), Oulema lichenis Voet.), cereal flies (Oscinella frit L., Oscinella pusila Meigen, Mayetiola destructor (Say), Phorbia securis Tiensuu etc.) were the most common in agrocenoses of grain crops in a harmful entomocomplex. Polyphagous insects, namely caterpillars of gnawing scoops (Scotia segetum Schiff., Scotia exclamationis L.), also caused significant damage in cereal crops. It was revealed that a complex of sucking pests is numerous on winter wheat, represented by wheat thrips (Haplothrips tritici Kurd.), Cereal aphids (Macrosiphum (Sitobion) avenae F., Schizaphis graminum Rond.), Grain sawflies (Cephus pygmaeus L., Trachelus tabidus F.), on spring wheat grain flea beetles (Phyllotreta vittula Redt., Chaetocnema aridula Gyll.) and wheat thrips, on spring barley – grain flea beetles and cereal aphids. Under favorable conditions for overwintering, warm, moderately humid weather in spring and dry weather in summer, active colonization and an increase in the number of phytophages led to their exceeding in 2.5–5.7 times of the economic threshold of harmfulness. Under these conditions, the number of grain bugs (Eurygaster integriceps Put., Е. austriacus Schrnk., Е. maura L., Aelia acuminata L., Dolycoris baccarum L.) in some years reached 8– 15 ind./m2 , ground beetles — up to 20 ind./m2, grain beetles — up to 17 ind./m2, cereal aphids — up to 50 ind./plant.

Cereal Aphid Species (Homoptera : Aphididae) Infesting Wheat Plants and their Aphidophagous Insects at El-Khattara District, Sharkia Governorate, Egypt

Studies on cereal aphids infesting wheat plants and their aphidophagous insects were carried out in newly reclaimed sandy area at El-Khattara district, Sharkia Governorate, Egypt during 2015-2016 and 2016-2017 growing seasons.The obtained results are summarized as follows:Four aphid species, i.e., Shizaphis graminum (Rondani), Rhopalosiphum maidis (Fitch), Rhopalosiphum padi (Linnaeus) and Macrosiphum avenae (Fabricius) were found infested wheat plants.Cereal aphids infested wheat plants from the first week of January till the last week of April. The highest populations of aphids were recorded in the first week of March and in the second week of April with counts of 711 and 1503 individuals/ sample in the first and second seasons, respectively.Six predaceous insect species belonging to four orders and five families were surveyed associated with aphid species infesting wheat plants. Coleopterous species were the most dominant, followed by the neuropterous ones, with general relative densities of 41.70 and 21.10 % of the total recorded predators, successively. Among all recorded predaceous species, Chrysoperla carnea (Stephens) , Coccinella undecimpunctat L., and Coccinella septempunctata L., were the most dominant species, comprised 21.10, 15.68 and 15.26 % of the total count of the predators, respectively. The total recorded predators showed that means of 1:61.62 and 1:118.73 predators: prey ratios in the first and second seasons, respectively.Five species of hymenopterous parasitoids were emerged from mummified individuals of cereal aphids, namely, Diaeretiella rapae (M’Intosh), Aphidius colemani Viereck, Aphidius matricariae Haliday, Ephedrus sp. and Praon sp. The most dominant parasitoids were D. rapae and A. colemani with general relative densities of 35.32 and 27.12% respectively. The fluctuations of the total percentages of parasitism indicated three peaks in the first season and two ones in the second season. The mean percentage of parasitism during the first season was relatively high (6.41%) in comparison with that in the second one (3.60%).The correlation between cereal aphids populations and percentages of parasitism in both seasons were positive high significant

Morphological Identification of Aphid Species Infesting Some Ornamental plants in Taif Governorate

Aphid species were surveyed and identified from 18 ornamental plant in different localities in Taif governorate, KSA through 2015/2016 seasons. Eleven aphid species were recorded only on 14 ornamental host plants. Rhodobium porosum, Brachyunguis tamarics and Acyrthosiphon pisum were recorded on Rosa damascene var trigintipetala. There were two aphid species were recorded on Tecoma stans; Brachyunguis tamarics and Aphis compositae. Aphis compositae was more abundant. One aphid species was collected and identified on Rosa damascena, this species was known as Rhodobium porosum. For Jasminum grandiflorum, Cestrum sp. and Tegetes marigold, only one aphid species was recorded; namely Myzus persica, this aphid species was observed with very high density on Cestrum sp., followed by Jasminum grandiflorum but the lowest abundant was recorded on Tegetes marigold. Brachyunguis tamarics also was the only recorded species on Hibiscus rosa-sinensis., it was observed in weak density. The four ornamental plants; Bougainvillea sp., Nerium oleander, schefflera actinophyll and Ruta graveolens, recorded no aphid infestation through the two tested seasons 2015 and 2016. Four aphid species were identified on Ocimum basilicum during the season; these species were Rhopalosiphum maidis, Aphis copmpositae, Macrosiphum avenae and Rhodobium porosum, the lowest observed abundant species was Rhodobium porosum. On Plectranthus amboinicus, there was only one recorded aphid species, it was identified as Macrosiphum avenae, and was recorded in high density. Brachynguis tamaricis was the only species recorded on Petunia sp. and Caesalpinia pulcherrima, was demonstrated with high density on petunia sp. On Rosa damascene var semperflorens, there were four recorded species namely as; Macrosiphum rosae, Macrosiphumavenae,

Effects of inter-annual landscape change on interactions between cereal aphids and their natural enemies

The agricultural intensification and the subsequent habitat changes in agroecosystem can strongly affect biological control services. We here examine the influence of inter-annual landscape change in wheat field area on interactions of cereal aphids and their natural enemies, as well as the efficacy of biological control using data collected from a 4-year experiment in Northwest China. Two hypotheses were tested. (i) Population densities decline following an inter-annual expansion of wheat crop proportion cover due to dilution and crowding effects. (ii) Species that are specialists or at higher trophic levels are more sensitive to bottom-up disturbance by inter-annual change in percent cover of wheat crop. Results showed the population densities of one cereal aphid (Macrosiphum avenae), one parasitic wasp (Aphidius avenae), two specialist predators (ladybirds: Hippodamia variegata and H. tredecimpunctata) and one hyperparasitic wasp (Pachyneuron aphidis) declined following the expansion of wheat crop areas, supporting the predictions of inter-annual dilution and crowding effects. In contrast, the populations of one cereal aphid (Schizaphis graminum), one parasitic wasp (A. gifuensis), two generalist predators (spiders: Pardosa astrigera; carabid beetles: Chlaenius pallipes), and two hyperparasitic wasps (Asaphes suspensus, and Alloxysta sp.) did not respond to inter-annual landscape change. The two hypotheses were partially supported but with noticeable exceptions, and the bio-control efficiency declined with the increase of the proportion cover of wheat field in agricultural landscape. Overall, different responses of cereal aphids and their natural enemies make it difficult but still possible to optimize inter-annual landscape change for enhancing the parasitism rate and predator-prey ratio.

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.

Strip cropping wheat and alfalfa to improve the biological control of the wheat aphid Macrosiphum avenae by the mite Allothrombium ovatum

Strip cropping of wheat ( Triticum aestivum ) and alfalfa ( Medicago sativa ) as a mechanism for improving the effectiveness of biological control of the wheat aphid ( Macrosiphum avenae ) by the mite ( Allothrombium ovatum ) was studied from 2002 to 2004 in Luancheng County, Hebei Province, China. Results showed that the strip cropping of wheat and alfalfa significantly increased the egg and larval densities of A. ovatum and the percentage of M. avenae parasitized by larval mites compared with the monoculture of wheat. The mean number of mites per parasitized aphid was also significantly higher in strip cropping than in wheat monoculture. The percentage of parasitized aphids was shown as a negative and logarithmical function of the mean population growth rate of wheat aphid, however such a relationship was statistically significant only in the strip cropping plots. The higher incidence of parasitism on alate than on apterous aphids indicated that parasitism of alate aphids by A. ovatum play an important role in facilitating A. ovatum dispersal and limiting wheat aphid population increase.

Characterization of a Facultative Endosymbiotic Bacterium of the Pea Aphid Acyrthosiphon pisum

The pea aphid U-type symbiont (PAUS) was investigated to characterize its microbiological properties. Fluorescence in situ hybridization (FISH) and electron microscopy revealed that PAUS was a rod-shaped bacterium found in three different locations in the body of the pea aphid Acyrthosiphon pisum: sheath cells, secondary mycetocytes, and hemolymph. Artificial transfer experiments revealed that PAUS could establish stable infection and vertical transmission when introduced into uninfected pea aphids. When 28 aphid species collected in Japan were subjected to a diagnostic PCR assay, four species of the subfamily Aphidinae (Aphis citricola, Aphis nerii, Macrosiphum avenae, and Uroleucon giganteus) and a species of the subfamily Pemphiginae (Colopha kansugei) were identified to be PAUS-positive. The sporadic incidences of PAUS infection without reflecting the aphid phylogeny can be best explained by occasional horizontal transfers of the symbiont across aphid lineages.

Analyzing and Modeling Temporal Disease Progress of Barley yellow dwarf virus Serotypes in Barley Fields

ABSTRACT Population dynamics of Padi avenae (PAV), Macrosiphum avenae (MAV), and Rhopalosiphum padi (RPV) virus serotypes of Barley yellow dwarf virus (BYDV) and of their main aphid vectors were studied in winter barley (Hordeum vulgare) fields for three successive years in western France. An epidemiological model of the spread of viruses in the field was developed based on vector populations as forcing variables and the population dynamics of each virus serotype. This model accurately simulated the kinetics of the epidemic for PAV serotypes, which are the most common ones. For RPV and to some extent for MAV, the results were less satisfactory. The occurrence and spread of PAV and MAV serotypes in the field was clearly and easily related to that of their main vector species. Conversely, the spread of RPV serotypes showed no consistent relationships with the dynamics of their vectors. Incidence of PAV in 1989 to 1990 and 1990 to 1991 showed a bimodal distribution, with maximums in fall (December) and spring (May) that were linked to fall infestations by R. padi and spring infestations by three (R. padi, Sitobion avenae, and Metopolophium dirhodum) or two (S. avenae and M. dirhodum) aphid species. In 1991 to 1992, the PAV infection curve was monomodal and mainly due to a primary spread of the virus by very large populations of alate R. padi. MAV incidence was low in fall and winter and reached a maximum in spring 1990 and 1991 related to the occurrence of S. avenae and M. dirhodum. RPV incidence was low every year, despite the abundance of its vector, R. padi. Mixed infections were more frequent than expected by chance and were assumed to be partly related to heterologous encapsidation. The occurrence of each serotype is discussed in relation to the time of crop infection and possible damage.

Population growth and structure in a variable environment : I. Aphids and temperature variation.

When a population experiences temporal changes in the vital rates due to environmental or biotic variation, change is not only expected in the rate of population growth but also in the structure of the population. In this study we present a method for transforming observed patterns (notably how vital rates change with temperature) into functions that can be used in population growth models and analysis of population structure. The method is exemplified by applying it to cohort studies in different constant temperatures of four species of aphids, Lipaphis erysimi (K.), Metopolophium dirhodum (Wlk.), Rhopaliosiphum padi and Macrosiphum avenae (F.). We use piece-wise linear functions to transform the vital rates of the cohort studies. The lifespans are divided into phases, each phase having linear rates. A projection matrix is formulated, where the elements are temperature dependent fecundities, survivorships and developmental rates. The major result is, contrary to what theory predicts as reasonable (Caswell 1989), that population structure of these aphid species will become almost fixed although the temperature varies. This result is consistent with findings of earlier field studies (Wiktelius 1982). A fixed population structure implies that it is possible to calculate the population growth rate on the basis of intrinsic rates of increase. By simulating different temperature regimes we also show that initial oscillations in the population structure dampen out after a few days. After initial oscillations, calculations of population growth using intrinsic rates of increase are consistent with calculations made by a matrix model.

The Effect of Artificial Infestation of Ears by Macrosiphum avenae (F.) on Germination and Seedling Emergence of Two Winter Wheat Cultivars

10 day infestation of two winter wheat cultivars, Regina and Zdar, by grain aphid Macrosiphum avenae (F.) (3 virgines per ear at the anthesis), caused up to 30 per cent loss of seed weight, and accelerated significantly seed germination. The percentage of seed germination was not influenced. First four days after emergence, the sprouts of the seed influenced by aphids were longer than the control, then shorter. After 8 days, the seedlings from aphid affected seeds had significantly lower dry matter than controls. Cv. Zdar was more sensitive than cv. Regina.

Field Populations of the Russian Wheat Aphid (Homoptera: Aphididae) and Other Cereal Aphids on Cool-Season Perennial Grass Accessions

Six species of cereal aphids infested field plots of perennial grass accessions of Festuca arundinacea Schreb. (tall fescue), Agropyron desertorum (Fisch. ex Link) Schultes (standard crested wheatgrass), and Dactylis glomerata L. (orchard grass) at Pullman and Central Ferry, Wash., in summer 1988. Seed of cool-season perennial grass accessions from the United States germplasm collection is routinely increased at Pullman and Central Ferry, Wash. Russian wheat aphid, Diuraphis noxia (Mordvilko) (Homoptera: Aphididae), assumed dominant status at Central Ferry and English grain aphid, Macrosiphum avenae (F.), was dominant at Pullman. Other species found were Metopolophium dirhodum (Walker), greenbug, Schizaphis graminum (Rondani), bird cherry-oat aphid,Rhopalosiphum padi (L.), and Sipha elegans del Guercio. Overall, aphid densities were highest in nonirrigated plots at Pullman (x aphids/five tillers = 191.87), intermediate in irrigated plots at Central Ferry (x = 47.86), and lowest in non irrigated plots at Central Ferry (x = 15.70). At Central Ferry, significantly fewer (P 0.05) aphids were recovered from F. arundinacea, than from A. desertorum and D. glomerata; however, aphid densities were higher on F. arundinacea at Pullman. Results indicate that cereal aphids pose a potential hazard to seed regeneration and should be monitored to ensure against loss of grass germ plasm. Also, results show that some commonly occurring Pacific Northwest perennial grasses have the potential to support natural populations of the Russian wheat aphid.

Effects of Constant and Fluctuating Temperatures on Developmental Rates and Demographic Statistics of the English Grain Aphid (Homoptera: Aphididae)

Relationships between temperature and developmental rate of immature apterous and alate English grain aphids, Macrosiphum avenae (F.), were studied in the laboratory using constant and fluctuating temperatures. Estimates of lower (4.0°C) and upper (24.6°C) developmental thresholds were determined using constant temperatures. Developmental rates and age-specific life table statistics were determined using fluctuating temperature regimes that simulated average and extreme low and high temperature conditions occurring during late spring in South Dakota. Developmental rates of cohorts exposed to low and average fluctuating temperatures were consistent with expected developmental rates based on a degree-day model incorporating lower and upper thresholds obtained from constant temperature studies. Developmental rate appeared to slow in M. avenae exposed to high fluctuating temperatures. Life table statistics expressed on a degree-day time scale differed among apterous and alate M. avenae exposed to identical temperature regimes. At each temperature regime, population growth rates of apterae exceeded those of alatae. On a degree-day time scale, population growth rates of both morphs were greatest at low temperatures and declined as temperature increased.

Development and Reproduction of the English Grain Aphid (Homoptera: Aphididae) on Wheat Cultivars Infected with Barley Yellow Dwarf Virus

Interactions among the English grain aphid, Macrosiphum (Sitobion) avenae (F.), and three wheat ( Triticum aestivum L.) cultivars infected with two isolates of barley yellow dwarf virus (BYDV) were investigated under laboratory conditions by caging individual aphids on leaves of healthy ‘Caldwell,’ ‘Abe,’ and ‘Talento’ wheat plants or plants infected with BYDV (P-PAV and RPV-NY isolates). M. avenae feeding on infected wheat had a significantly shorter (P ≤ 0.05) developmental time, a greater fecundity, and a greater intrinsic rate of natural increase ( r m) than aphids feeding on noninfected plants. These results suggest that BYDV and M. avenae interact for their mutual benefit, resulting in a higher potential for population growth of the virus and the vector. The wheat cultivar ‘Caldwell’ was found in this and previous studies to have a degree of tolerance to BYDV as indicated by milder symptoms. Resistance to virus production also was detected for the P-PA V-infected ‘Caldwell’ wheat, which had significantly lower ELISA values (i.e., lower virus concentration) than ‘Abe’ wheat. M. avenae also had a significantly reduced fecundity on ‘Caldwell’ compared with that on ‘Abe’ and ‘Talento’ wheats infected with BYDV. No significant differences were observed in M. avenae fecundity on BYDV-free cultivars. The results suggest that infection with BYDV might improve the nutritional quality of wheat to M. avenae , resulting in changes in the fecundity of the vector. These changes were greater with the BYDV-sensitive ‘Abe’ and ‘Talento’ cultivars than with the tolerant ‘Caldwell’ wheat cultivar.

Influence of Plant Growth Stage on Cereal Aphid Reproduction

The objective of this research was to determine the influence of the stage of growth of host plants upon the fecundity of cereal aphids. This information is useful in evaluating the potential for cereal aphid movement between, and their colonization of, a sequence of field crops in the Northern Plains and in understanding the epidemiology of plant virus diseases transmitted by cereal aphids. Aphid fecundity was tested in growth chambers on spring wheat (Triticum aestivum L.), spring barley (Hordeum vulgare L.), sorghum [Sorghum bicolor (L.) Moench], and maize (Zea mays L.) when plants were in the seedling (2—3 leaf), boot, heading, and flowering stages of growth. Aphid fecundity was also compared on vernalized and nonvernalized winter wheat. The aphids tested were the greenbug (GB) [Schizaphis graminum (Rondani)], the English grain aphid (EGA) [Macrosiphum (Sitobion) avenae (F.)], the bird‐cherry oat aphid (RP) [Rhopalosiphum padi (L.)], and the corn leaf aphid (CLA) [R. maidis (Fitch)]. The results of the tests showed that GB and RP reproduced more on headed wheat than on earlier stages of wheat growth. CLA fecundity was significantly greater on seedling barley than on later stages of growth, but there were no significant differences in GB, RP, and EGA reproduction on barley at the several stages of growth. Seedling maize was virtually immune to RP and CLA colonization; however, GB, RP, and CLA reproduction was greater on seedling sorghum than on older plants. No significant differences were detected in the fecundity of GB, RP, or EGA on vernalized versus nonvernalized winter wheat. The results are interpreted in the context of cereal aphid field biology and stage of crop development in the Northern Plains.

Yield Losses in Winter Grains Caused by Cereal Aphids (Homoptera: Aphididae) in South Dakota

Yield losses in ‘Rough Rider’ winter wheat, Triticum aestivum L., and ‘Cougar’ winter rye, Secale cereale L., caused by feeding of Schizaphis graminum (Rondani), Rhopalosiphum padi (L.), and Macrosiphum avenae (F.) were each measured for 3 yr in South Dakota fields. Caged plots were artificially colonized with aphids for 10 d when plants were in three different growth stages; losses in components of yield were measured at harvest. Greatest losses of yield were caused when aphids fed during the seedling (2-3 leaf) stage in autumn; mean densities of 25-30 aphids per stem caused reductions of 50% in some components of yield at this stage. Lower yield losses were recorded for similar aphid population densities when they fed in spring during the boot stage (immature in florescence invested in leaf sheath), and no losses were observed when aphids fed on mature (dough stage) plants. Schizaphis graminum and R. padi were more damaging than M. avenae at similar population densities. Winter wheat was more vulnerable than rye to yield losses caused by aphid feeding.

Spatial Distributions of Cereal Aphids (Homoptera: Aphididae) in Winter Wheat and Spring Oats in South Dakota

Taylor's power law, Iwao's patchiness regression, and the negative binomial distribution with a common value of k were used to model variance/mean relationships of populations of four species of cereal aphids, Schizaphis graminum (Rondani), Macrosiphum avenae (F), Rhopalosiphum padi (L.), and Rhopalosiphum maidis (Fitch), occurring in winter wheat and spring oat fields in South Dakota. Taylor's power law generally provided a better model of variance/mean relationships than did the other models. Intercepts of Taylor's power law regressions (log a) varied among populations of some cereal aphid species occurring on different host crops. Regression slopes (b) generally did not differ among populations inhabiting different crops; however, b did differ among populations of R. padi sampled from spring oats and winter wheat. Power-law parameters were independent of field and year at which populations were sampled and time during the growing season at which samples were taken. These results suggest that marked changes in environment (e.g., different host crops) influenced spatial distributions of cereal aphid populations and, hence, the value of power-law parameters. However, for populations inhabiting either host crop, power-law parameters seemed to be independent of temporal and spatial variation.

Damage to Wheat by Macrosiphum avenae (F.) (Homoptera: Aphididae) in Northwest China

Wheat yield loss from English grain aphid, Macrosiphum avenae (F.), feeding was investigated in central Shaanxi Province, the People’s Republic of China, in 1982, 1984, and 1985. Aphids were caged on individual wheat heads at emergence, flowering, milk, and soft dough stages of wheat head development. Maintaining a constant number of aphids (0, 2, 5, 10, 20, or 30) (1982 and 1984) on wheat heads resulted in significant regressions of seeds per head and grams per 1,000 seeds on cumulative aphid days. Longer exposure to aphid feeding or larger numbers of aphids caused higher wheat yield reductions, but no differences in regression slopes were obtained when inoculation was made at head emergence, flowering, or milk stages. Inoculating heads with 0, 1, 3, 6, 9, or 12 aphids at head emergence, flowering, or milk, and allowing them to reproduce in cages (1985), resulted in a significant regression of grams per 1,000 seeds on cumulative aphid days, but the slope of the regression line was significantly lesssteep than in 1982 and 1984. Based on acceptable yield losses (5%) in this area of the People’s Republic of China and percent yield losscaused by various levels of aphids caged on wheat heads, an economic threshold level of four to five aphids per head up to and during flowering stage of wheat head development was established.

Cereal Aphid Populations in Winter Wheat: Spatial Distributions and Sampling with Fixed Levels of Precision

Taylor's power law and Iwao's patchiness regression were used to analyze spatial distributions of four aphid species, Schizaphis graminum (Rondani), Macrosiphum avenae (F.), Rhopalosiphum padi (L.), and R. maidis (Fitch), in 0.3-m samples taken from winter wheat fields. Taylor's power law generally provided a better description of variance/mean relationships for the species than did Iwao's patchiness regression. All species exhibited aggregated patterns of spatial distribution, but patterns of distribution differed among some species. Sample size requirements for fixed levels of precision and sequential sampling plans of fixed levels of precision were determined by utilizing estimated variance/mean relationships obtained from Taylor's power law regressions. Sample size requirements for estimation of population means with fixed levels of precision were greatest for R. padi , and decreased in the order M. avenae , S. graminum , and R. maidis .

Yield Losses in Spring Barley Caused by Cereal Aphids (Homoptera: Aphididae) in South Dakota

Yield losses in ‘Larker’ spring barley, Hordeum vulgare L., due to feeding of Schizaphis graminum (Rondani), Macrosiphum avenae (F.), Rhopalosiphum padi (L.), and R. maidis (Fitch) were measured in 1979, 1980, and 1984 in South Dakota fields. Caged plots were artificially colonized with aphids for 10 days when plants were in three different growth stages; losses in components of yield were measured at harvest. Greatest losses in yield were caused by aphids feeding during the seedling (2–3 leaf) stage; mean densities of 25–30 aphids per stem resulted in losses of 50% in some components of yield at this stage. Lower yield losses were recorded for similar aphid population densities when aphids fed during the boot stage (immature inflorescence invested in leaf sheath) and no losses were observed when plants were mature (dough stage). S. graminum and R. padi were more damaging than M. avenae or R. maidis at similar population densities. Populations of R. maidis developed only in the furled leaves of the growing tip.

Cereal Aphid (Homoptera: Aphididae) Preferences for and Reproduction on Some Warm-Season Grasses

Preferences and reproduction of Schizaphis graminum (Rondani), Macrosiphum (Sitobton) avenae (F.), Rhopalosiphum padi (L.), and R. maidis (Fitch) were tested on 13 species (9 genera) of native North American warm-season grasses under controlled conditions in environmental chambers. In six of the eight tests (involving S. graminum, M. avenae, R. padi ), none of the grasses was as attractive to alighting aphids as the control, Hordeum vulgare L. Seedling Panicum virgatum and mature Eragrostis trichodes were as attractive to R. maidis as the control. Schizaphis graminum reproduced successfully on seven seedling grasses, M. avenae on four, R. padi on two, and R. maidis on one. Only R. maidis reproduced successfully on the mature grasses (six species). The Andropogon spp. were virtually immune to aphid colonization. Aphid preferences for particular grasses were often a good index to their reproductive success on them. Warm-season grasses are probably not as important as alternative hosts of cereal aphids in the Northern Plains as Agropyron spp. or certain weed grasses.