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Twelve perennial small grain cultivars were examined for eight characteristics favorable to management of greenbug, Schizaphis graminum (Rondani). A greenbug-susceptible variety of hard red winter wheat, Triticum aestivum L., and a greenbug-resistant hard red winter wheat variety were used as checks. Eight of the 12 perennial small grain cultivars (including X Triticosecale spp. / Thinopyrum intermedium // X Triticosecale spp., X Triticosecale spp. / Thinopyrum ponticum // X Triticosecale spp., Thinopyrum ponticum / Triticum aestivum var. Eltan, X Agrotriticum spp. (PI550715) / Tripsacum dactyloides var. Spitzer, and Hordeum vulgare var. MT2 / Tripsacum dactyloides var. Spitzer) had at least one favorable greenbug management characteristic. Cultivars that included X Triticosecale spp. and either Thinopyrum intermedium (Host) Barkworth & D.R. Dewey or T. ponticum wheatgrass in their genetic background had the most favorable characteristics. [ABSTRACT FROM AUTHOR]

Cooperative projects by various national and state agencies in the last 10 years have resulted in the establishment of an effective saltcedar (Tamarisk sp.) biological control agent, the tamarisk beetle (Diorhabda spp.). Three species of tamarisk beetles have been established in different regions of Texas, typically based on their climatic adaptation. The beetles defoliate saltcedar over multiple seasons, weakening and, during 3 to 5 years, eliminating large stands of this invasive plant. Another saltcedar biological control agent, the splendid tamarisk weevil, Coniatus splendidulus F., is also established in the United States from undocumented introductions. Surveys of saltcedar for evidence of biological control in the eastern Texas Panhandle and western Oklahoma during the summer of 2012 following landowner reports of beetle infestations, and previous release efforts along the Canadian River in Texas resulted in new state and county records for Diorhabda carinata (Faldermann), D. elongata (Brullé), and C. splendidulus F. D. carinata x D. elongata hybrids were recorded for the first time in Oklahoma, from five western counties. In Texas, hybrids of D. carinata x D. elongata, D. carinata, D. elongata, and C. splendidulus were recorded from five, 16, one, and three eastern Panhandle counties, respectively. A history of the release efforts for establishment of Diorhabda spp. from 2004-2010 in the Texas Panhandle is included. [ABSTRACT FROM AUTHOR]

Seasonal adaptations to daylength often limit the effective range of insects used in biological control of weeds. The leaf beetle Diorhabda carinulata (Desbrochers) was introduced into North America from Fukang, China (latitude 44° N) to control saltcedars (Tamarix spp.), but failed to establish south of 38° N latitude because of a mismatched critical daylength response for diapause induction. The daylength response caused beetles to enter diapause too early in the season to survive the duration of winter at southern latitudes. Using climate chambers, we characterized the critical daylength response for diapause induction (CDL) in three ecotypes of Diorhabda beetles originating from 36, 38, and 43° N latitudes in Eurasia. In a field experiment, the timing of reproductive diapause and voltinism were compared among ecotypes by rearing the insects on plants in the field. CDL declined with latitude of origin among Diorhabda ecotypes. Moreover, CDL in southern (<39° N latitude) ecotypes was shortened by more than an hour when the insects were reared under a fluctuating 35-15°C thermoperiod than at a constant 25°C. In the northern ( >42° N latitude ) ecotypes, however, CDL was relatively insensitive to temperature. The southern ecotypes produced up to four generations when reared on plants in the field at sites south of 38° N, whereas northern ecotypes produced only one or two generations. The study reveals latitudinal variation in how Diorhabda ecotypes respond to daylength for diapause induction and how these responses affect insect voltinism across the introduced range. [ABSTRACT FROM AUTHOR]

The greenbug, Schizaphis graminum (Rondani) (Hemiptera: Aphiidae), is a major aphid pest of small grains and sorghum, Sorghum bicolor (L.) Moench. Greenbugs extract juice and inject toxin, killing seedlings or limiting the yield of older plants. Understanding greenbug biology and how biotypes develop is important for evaluating and developing sorghum with durable resistance. Prereproductive period, fecundity, and longevity of greenbug biotypes E and I were assessed on susceptible 'RTx430' sorghum at four cycling temperatures of 10-23, 14-27, 18-31, and 22-35°C in an incubator. A photoperiod of 14:10 (L:D) h corresponded with daily warm and cool temperatures. Greenbug fitness was more affected by temperature than biotype. Greenbug prereproductive period, total fecundity, and longevity did not differ among temperature regimes except at the warmest regime (22-35°C), at which all parameters were greater for biotype E than biotype I. The prereproductive period of greenbug biotypes E and I combined was more than twice as long at the coolest temperature of 10-23°C as at 22-35°C. Greenbugs produced a maximum average of 3.3 more nymphs per day at warmer than cooler temperature regimes. Average total fecundity was greatest at 10-23°C, with fewest nymphs being produced at 22-35°C. Longevity of greenbug biotypes E and I combined was 6 times longer at 10-23°C than at 22-35°C. This study provides information on optimal temperatures under which to evaluate damage to sorghum being developed for resistance to different biotypes of greenbug. [ABSTRACT FROM AUTHOR]

False brome grass, Brachypodium distachyon (L.) Beauv, has been proposed as a new model species to bridge rice and temperate cereal crops for genomics research. However, much basic information for this species is still lacking. In this study, six diploid B. distachyon (2n = 2x = 10) accessions (Bd1-1, Bd2-3, Bd3-1, Bd18-1, Bd21 and BD29) were evaluated for their response to infestation by two cereal aphid pests of common wheat (Triticum aestivum L.): the greenbug, Schizaphis graminum Rondani, and the Russian wheat aphid (RWA), Diuraphis noxia Mordvilko. Through database mining of B. distachyon expressed sequence tag (EST) and genomic DNA sequences, 160 EST- and 21 genomic microsatellite markers were developed and used to evaluate genetic diversity among the B. distachyon accessions. All six accessions were resistant to RWA biotype RWA1 but showed distinct responses to feeding by greenbug biotypes C and E, as well as RWA2 RWAs. Although microsatellite-based genetic diversity among different accessions was generally low, Bd1-1 and BD29 were the most diverged from the other four lines. The genetic divergence was correlated with geographical distances between the Brachypodium accessions. Comparison of simple sequence repeat polymorphisms in three inbred lines (Bd2-3, Bd3-1 and Bd18-1) with their respective original parental lines revealed no effect of inbreeding on genetic diversity. Phylogenetic analysis suggested that Aegilops tauschii (Coss.) Schmal., the D genome donor of common wheat, was closer to B. distachyon than to rice. The greenbug - B. distachyon system seems to be a model of choice for plant-aphid interaction studies in the grass genome. [ABSTRACT FROM AUTHOR]

The abundance and distribution of microsatellites, or simple sequence repeats (SSRs) were explored in the expressed sequence tag (EST) and genomic sequences of the pea aphid, Acyrthosiphon pisum (Harris), and the green peach aphid, Myzus persicae (Sulzer). A total of 108 newly developed, together with 40 published, SSR markers were investigated for their cross-species transferability among six aphid species. Genetic diversity among six greenbug, Schizaphis graminum (Rondani) and two Russian wheat aphid, Diuraphis noxia (Kurdjumov) biotypes was further examined with 67 transferable SSRs. It was found that the pea aphid genome is abundant in SSRs with a unique frequency and distribution of SSR motifs. Cross-species transferability of EST-derived SSRs is dependent on phylogenetic closeness between SSR donor and target species, but is higher than that of genomic SSRs. Neighbor-joining analysis of SSR data revealed host-adapted genetic divergence as well as regional differentiation of greenbug biotypes. The two Russian wheat aphid biotypes are genetically as diverse as the greenbug ones although it was introduced into the USA only 20 years ago. This is the first report of large-scale development of SSR markers in aphids, which are expected to have wide applications in aphid genetic, ecological and evolutionary studies. [ABSTRACT FROM AUTHOR]

Coccinellids are important natural enemies of aphid pests in wheat, Triticum aestivun em Thell, in the Great Plains of the United States.Coccinellid community development in wheat fields is unpredictable; therefore, precise, efficient sampling methods for coccinellids are needed for use in integrated pest management research and decision making. Our objectives were to compare removal sampling with quadrat sampling for estimating population density of adult and larval coccinellids in winter wheat, and to determine if timed count sampling and sweepnet sampling were useful for estimating adult and larval coccinellid densities. Removal sampling accurately estimated population densityfor adults of most species but consistently underestimated larval density. Timed count samples and sweepnet samples were significantly correlated with absolute density of both larval and adult coccinellids.Regression models were developed to convert estimates of relative toestimates of absolute population density. Depending on sampling method and life stage, models included the number of tillers per 0.3 m, wheat plant growth stage, plant height, and the number of aphids per tiller as variables; R{sup}2{end} values ranged from 0.89 to 0.93. Sweepnet sampling was more precise per unit of effort than timed count, quadrat, or removal sampling for estimating adult coccinellid density. Removal sampling (removing all coccinellids seen during 2 successive 15-min searches from each of 9 plots (25 m{sup}2{end}) was the least efficient method. [ABSTRACT FROM AUTHOR]

Understanding tritrophic effects of resistant crops on natural enemies feeding on pests is important for developing resistant plants while conserving natural enemies. The effect on convergent lady beetles, Hippodamia convergens Guerin-Meneville, fed greenbugs, Schizaphis graminum (Rondani), reared on resistant sorghum, Sorghum bicolor (L.) Moench, was assessed. Convergent lady beetles from sorghum fields were paired and allowed to mate. F1 progeny were reared at a photoperiod of 14:10 light:dark hours at 23 or 30°C and fed daily with a known number of biotype I greenbugs from resistant PI550607 or susceptible RTx430 sorghum. Lady beetle eggs hatched 1 day later at 23°C (3.0 days) than at 30°C. Larvae completed development in 0.75 more day and pupae developed in 6.0 versus 3.0 days at 23 than at 30°C. Lady beetles consumed similar numbers of greenbugs from either genotype of sorghum, but larvae and adults consumed 1.7 and 2.5 times more greenbugs at 23 than at 30°C, respectively. Each lady beetle adult at 23°C consumedan average of 17,124 greenbugs. Adult lady beetles were paired in four combinations depending on the sorghum source of greenbugs from which they had been fed. Most eggs were produced (2,893 eggs) and hatched (2,657 or 91.0%) per lady beetle fed greenbugs from susceptible sorghum at 23°C. [ABSTRACT FROM AUTHOR]