Assessment of methods for estimating the numbers of aphids (Hemiptera: Aphididae) in Cereals

1982 ◽  
Vol 72 (4) ◽  
pp. 675-685 ◽  
Author(s):  
Alan M. Dewar ◽  
Godfrey J. Dean ◽  
Ray Cannon
Keyword(s):  
Field Studies ◽  
Accurate Method ◽  
Sitobion Avenae ◽  
Cereal Aphid ◽  
Metopolophium Dirhodum ◽  
Aphid Density ◽  
Very High ◽  
Vacuum Sampling

AbstractVisual counting was found to be the most accurate method of estimating cereal aphid numbers in field studies in England. Vacuum sampling decreased in efficiency as aphid density increased, but could be a useful alternative to visual counts at very low aphid densities when the latter became too time-consuming. Cutting tillers for later washing in the laboratory was less efficient than visual counting as aphids, especially Metopolophium dirhodum (Wlk.), fell off the plants during sampling, but this method was useful in determining the proportion of different morphs of Sitobion avenae (F.) present at very high densities.

scholarly journals Comparison of Field Population Growths of Three Cereal Aphid Species on Winter Wheat

2011 ◽  
Vol 39 (No. 2) ◽  
pp. 61-64 ◽  
Author(s):  
V. Jarošík ◽  
A. Honěk ◽  
A. Tichopád
Keyword(s):  
Winter Wheat ◽  
Rhopalosiphum Padi ◽  
Intrinsic Rate ◽  
Aphid Species ◽  
Population Increase ◽  
Intrinsic Rate Of Increase ◽  
Cereal Aphid ◽  
Metopolophium Dirhodum ◽  
Aphid Density ◽  
Rate Of Increase

Population growths of three aphid species colonising winter wheat stands, Metopolophium dirhodum, Rhopalosiphum padi and Sitobion avenae, were analysed by regression method. The calculations were based on counts in 268 winter wheat plots at 3 or 7 day intervals over 10 (leaves) or 6 (ears) years. The population dynamics of a particular species differed widely between years. Density independent exponential growth of the population was most common, but its rate differed significantly between species, and for S. avenae also between populations on leaves and ears, on which the populations grew fastest. Field estimates of the intrinsic rate of increase derived from the exponential growths ranged between 0.010–0.026 in M. dirhodum, 0.0071–0.011 in R. padi, and between 0.00078–0.0061 and 0.0015–0.13 in S. avenae on leaves and ears, respectively. In the populations with the most vigorous population growth, S. avenae on ears and M. dirhodum on leaves, the rate of population increase significantly decreased with increasing aphid density.  

scholarly journals Influence of Plant Diversity on the Numerical Response ofEriopis connexa(Coleoptera: Coccinellidae) to Changes in Cereal Aphid Density in Wheat Crops

2013 ◽  
Vol 2013 ◽  
pp. 1-8 ◽  
Author(s):  
María C. Tulli ◽  
Dora M. Carmona ◽  
Ana M. Vincini
Keyword(s):  
Plant Diversity ◽  
Aphid Species ◽  
Linear Increase ◽  
Numerical Response ◽  
Cereal Aphids ◽  
Cereal Aphid ◽  
Higher Plant ◽  
Metopolophium Dirhodum ◽  
Aphid Density ◽  
Eriopis Connexa

Cereal aphids cause economic injury to wheat crops. In Argentina,Eriopis connexais an indigenous ladybird. In the present study, the numerical response ofE. connexato changes in aphid density on wheat crops with high and low plant diversity was investigated. The study was carried out in Balcarce, Buenos Aires, Argentina, from September to December 2007 and 2008, on two wheat crops with either a higher plant diversity (HPD) with refuge strips or a lower plant diversity (LPD) without refuge strips. Crops were sampled every week and the abundance of aphids andE. connexawas recorded. The dominant aphid species wereSchizaphis graminum, Metopolophium dirhodum,andSitobion avenae.Eriopis connexashowed a linear increase in the numerical response to an increase in aphid density, which varied in space and time. The abundance ofE. connexaincreased in relation to the crop development and aphid population and was higher in the HPD than in the LPD system. This predator increased its reproductive numerical response only in 2008, with a significant liner response in the HPD system. This suggests that the potential ofE. connexaas a predator of cereal aphids also increases directly in proportion to landscape vegetal diversity.

Comparing growth patterns among field populations of cereal aphids reveals factors limiting their maximum abundance

2006 ◽  
Vol 96 (3) ◽  
pp. 269-277 ◽  
Author(s):  
A. Honek ◽  
V. Jarosik ◽  
A.F.G. Dixon
Keyword(s):  
Exponential Growth ◽  
Rhopalosiphum Padi ◽  
Growth Patterns ◽  
Aphid Population ◽  
Cereal Aphids ◽  
Cereal Aphid ◽  
Metopolophium Dirhodum ◽  
Density Dependent ◽  
Maximum Abundance ◽  
Aphid Density

AbstractCereal stands in central Europe are commonly infested with three species of aphids that may become serious pests. With increasing abundance, the proportion of a particular species in the total aphid population may remain constant, suggesting a density-independent exponential growth, or the proportion can change, suggesting density-dependent constraints on growth. The constraints that affect particular species, and thus their relative abundance, were studied. The proportionality between maximum abundances of the cereal aphids was studied using a 10-year census of the numbers of aphids infesting 268 winter wheat plots. For two species their abundance on leaves and ears was compared. With increasing aphid density the maximum abundance of Rhopalosiphum padi (Linnaeus) remained proportional, but not that of Sitobion avenae (Fabricius), which was constrained by the smaller surface area of ears compared to leaves. There was no evidence of inter-specific competition. Maximum abundance of R. padi and Metopolophium dirhodum (Walker) on leaves did not change proportionally as the proportion of M. dirhodum decreased with increasing overall aphid density. This decrease was probably caused by the restricted distribution of M. dirhodum, which is confined to leaves, where space is limiting. No change in proportion between populations was detected when the average densities were below 0.54 aphids per leaf or ear. Non-proportional relationships between aphid populations appeared to be due to spatial constraints, acting upon the more abundant population. Detecting the limitation of population growth can help with the assessment of when density-independent exponential growth is limited by density-dependent factors. This information may help in the development of models of cereal aphid population dynamics.

Anomalies: The Winner's Curse

1988 ◽  
Vol 2 (1) ◽  
pp. 191-202 ◽  
Author(s):  
Richard H Thaler
Keyword(s):  
Field Studies ◽  
Risk Averse ◽  
Common Phenomenon ◽  
Winner's Curse ◽  
Winner’S Curse ◽  
Empirical Question ◽  
Common Value ◽  
Winning Bidder ◽  
Common Value Auction ◽  
Very High

Next time that you find yourself a little short of cash for lunch, try the following experiment in your class. Take a jar and fill it with coins, noting the total value of the coins. Now auction off the jar to your class (offering to pay the winning bidder in bills to control for penny aversion). Chances are very high that the following results will be obtained: (1) the average bid will be significantly less than the value of the coins (bidders are risk averse); (2) the winning bid will exceed the value of the jar. Therefore, you will have money for lunch, and your students will have learned first-hand about the “winner's curse.” The winner's curse cannot occur if all the bidders are rational, so evidence of a winner's curse in market settings would constitute an anomaly. However, acting rationally in a common value auction can be difficult. Solving for the optimal bid is not trivial. Thus, it is an empirical question whether bidders in various contexts get it right or are cursed. I will present some evidence, both from experimental and field studies, suggesting that the winner's curse may be a common phenomenon.

scholarly journals Genetic structure and clonal diversity of an introduced pest in Chile, the cereal aphid Sitobion avenae

Heredity ◽  
2005 ◽  
Vol 95 (1) ◽  
pp. 24-33 ◽  
Author(s):  
C C Figueroa ◽  
J-C Simon ◽  
J-F Le Gallic ◽  
N Prunier-Leterme ◽  
L M Briones ◽  
...  
Keyword(s):  
Genetic Structure ◽  
Clonal Diversity ◽  
Sitobion Avenae ◽  
Cereal Aphid ◽  
Introduced Pest

Infidélité paléomagnétique observée dans une formation lacustre varvée quaternaire dite: "argiles d'Eybens" (Grenoble, France)

1982 ◽  
Vol 19 (6) ◽  
pp. 1196-1217 ◽  
Author(s):  
Daniel Biquand
Keyword(s):  
Remanent Magnetization ◽  
Axial Direction ◽  
Field Studies ◽  
Particle Orientation ◽  
Easy Magnetization ◽  
Magnetization Direction ◽  
Continuous Field ◽  
Very High ◽  
Different Levels ◽  
Thermal Remanent Magnetization

We have investigated the properties of natural magnetization of a lacustrine interglacial Riss–Würm deposit near Grenoble (France). Made up of accumulated argillite 250 m thick, this deposit comprises annual varves with an average thickness of 0.5 cm.The magnetic viscosity of this sediment is not very high, and we have demonstrated that the characteristic magnetization, measured after a moderate thermal treatment (between 160 and 220 °C) followed by alternating field demagnetization with maximum intensity at 200 Oe (15.9 × 103 A/m), is possibly a detrital magnetization carried by the magnetite (thermomagnetic and strong continuous field studies).On a local scale (area of about 100 m2), the direction of this magnetization remains very homogeneous within each horizon; sampling restricted to about 10 sites 1 m apart indicates for each level a mean direction of magnetization with a high accuracy: α95 = 1–2°, k = 500–2500. The aveage direction calculated by this method for different levels indicates significant stratigraphic variations (attaining an inclination of 20° and a declination of 50°), which are reached rapidly (from 1 to few degrees per year). Such variations cannot be reasonably attributed to changes in the directions of the Earth's magnetic field.A study of the acquired anisotropy of the thermal remanent magnetization indicates a magnetic anisotropy that is related to the lithological structure of the sediment and shows a strong intensity: the maximum divergence between the field direction and the acquired thermal remanent magnetization direction in this field varies, with individual samples, between 9 and 50°. The study of the properties of this anistotropy demonstrates the "infidelity" of the detrital magnetization: for one of the small vertical sequences studied for anisotropy the characteristic magnetization of a specified level has a direction nearer the axial direction of easy magnetization when the anisotropic intensity is large. This infidelity may be caused by different factors influencing the deposition of the sediment, particularly the variable directions of water flows determining the particle orientation. [Journal Translation]

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