geoscience.net logo
+ Resolve Article
+ Follow Us
Follow on FacebookFollow on Facebook
Follow on TwitterFollow on Twitter

+ Translate
+ Subscribe to Site Feed
GeoScience Most Shared ContentMost Shared Content

Regulation mechanisms in the population dynamics of phytophagous pests


, : Regulation mechanisms in the population dynamics of phytophagous pests. Berichte ueber Landwirtschaft Sonderheft 0(209): 54-67

The processes by which the populations of plant pests in arable land are regulated are demonstrated by the population dynamics or two groups of animals which differ extremely with respect to their ecology: the cyst nematodes as representatives of stationary pests, and cereal aphids as representatives of migratory species which each year recolonize the field. - A well-functioning mechanism of self-limitation presents the populations of cyst nematodes from destroying their own resources by overpopulation. The population level which cannot be surpassed depends essentially on the potential of increase which in turn is determined by the degree of susceptibility of the field crops: under resistent varieties the equilibrium density will be at a rat the potential of increase can be lowered likewise by the administration of large quantities of organic matter. If high nematode densities are permanently present for a long time a community of natural enemies, consisting for a considerable part of nematode-parasitic fungi, will build up in the long run and produce a kind of decline-effect. This effect comes, however, with a consider-able delay and is largely influenced by the external conditions. It is until now not possible, therefore, to exploit it purposefully. - Cereal aphids have an enormous potential of increase and can reach high population densities within very short rime if they are not checked by natural enemies. Among these are the syrphids key factors. It depends on the speed of their aggregation response whether or not an aphid outbreak will occur. In the experimental areas around Stuttgart they stop the aphids population increase usually so early that the crop remains undamaged. In the outbreak areas of northern Germany they arrive in the majority of years so (ate in the cereal crops that they cannot prevent an outbreak any longer. The possible causes are discussed. In spite of the fact that beneficial influences of hibernation and feeding habitates on the efficiency of syrphids cannot be proven in the adjacent fields on account of the great mobility of the hover flies, there is enough circumstantial evidence that the structure of the agroecosystem is of major significance.

US$29.90


Other references

Terada Torahiko, 1934: On a regularity in topographical features of northeast Japan. Proceedings of the Imperial Academy (Tokyo) 10(2): 65-68

Buehler, J.W.; Caum, J.; Alles, S.J., 2017: Public Health and the Pope's Visit to Philadelphia, 2015. Pope Francis visited Philadelphia for 2 days during September 2015. Preparedness functions managed by the Philadelphia Department of Public Health (PDPH) were similar to those of other mass gatherings but also required accommodation of special sec...

Furnham, A., 2008: Relationship among four Big Five measures of different length. This study examined the relationship between three short measures of the Big Five. 100 participants completed the 60-item NEO-FFI, the 10-item Personality Inventory, the 5-item Single-Item Measure of Personality, as well as estimating their own NE...

Gandevia, B., 1973: The Australian contribution to the history of the pneumoconioses. Medical History 17(4): 368-379

Doerschner, K.; Maloney, L.T.; Boyaci, H., 2011: Perceived glossiness in high dynamic range scenes. We investigated how spatial pattern, background, and dynamic range affect perceived gloss in brightly lit real scenes. Observers viewed spherical objects against uniform backgrounds. There were three possible objects. Two were black matte spheres...

Morita M.; Takahasi Yutaka, 1989: Groundwater management in Tokyo. Pages 155-166 1989

Bui, V.Nghia.; Mizutani, T.; Nguyen, T.Hoang.; Trinh, D.Quang.; Awad, S.S.A.; Minoungou, G.L.; Yamamoto, Y.; Nakamura, K.; Saito, K.; Watanabe, Y.; Runstadler, J.; Huettmann, F.; Ogawa, H.; Imai, K., 2014: Characterization of a genetic and antigenic variant of avian paramyxovirus 6 isolated from a migratory wild bird, the red-necked stint (Calidris ruficollis). A hemagglutinating virus (8KS0813) was isolated from a red-necked stint. Hemagglutination inhibition and neutralization tests indicated that 8KS0813 was antigenically related to a prototype strain, APMV-6/duck/Hong Kong/18/199/77, but with an 8- a...

Villemin, P.; Quemener, J., 1987: Comparison of three methods of measuring cation exchange capacity by potassium diffusion in soil columns. This paper presents a method of measuring potassium diffusion in small soil columns. Excess of potassium is located at one end of a closed column filled with soil and wetted to 2/3 field capacity. Diffusion was measured on 59 different soils. This...

Meder, J.F.; Dacher, J.N.; Krausé, D., 2007: Is an evaluation required at the third cycle?. Journal de Radiologie 88(7-8 Pt 1): 927-928

Neirinckx, L., 1965: Cationic interactions in the absorption of calcium by red beet root slices. Ca45 was used to follow the absorption of Ca by red beet slices. The interaction of the cations K+, Na+, Mg++ and Ba++ was observed. The interpretation of the results according to the kinetic theories of Epstein and Hagen reveals the existence of...