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At least 271 records · Page 15Linked to original sources
PubMed2001

Mating disruption of Plodia interpunctella in small-scale plots: effects of pheromone blend, emission rates, and population density.

An indoor mating disruption experiment was performed on the stored-product pest Plodia interpunctella. The female of this species emits a four-component pheromone blend consisting of Z9,E12-14 : OAc, Z9,E12-14 : OH, Z9,E12-14 : Ald, and Z9-14 : OAc. Mating of Plodia interpunctella was disrupted up to 93% by using synthetic pheromone in small-scale plot experiments. The study was performed in 2.5 m x 2.5 m x 2.5 m polythene cubicles housed in a greenhouse, and pheromones were released by MSTRS spraying every 15 min. The disruption effect was tested at different doses 0.075, 0.75, and 3.75 mg/spray (corresponding to 5, 50, and 250 microg/min), different pheromone formulas (one-component (Z9,E12-14 : OAc) and four-component), and at different population densities (10, 20, and 30 individuals, equivalent to 0.32, 0.64, and 0.96 individuals/m2). The moths were released into the cubicles and recaptured 24 hr later. The females were checked for spermatophore presence indicating successful mating. The mating was significantly suppressed in all treatments compared to the control. There was, however, no difference in mating activity between the one-component and four-component disruptants. In addition, EAG measurements were conducted with a portable device to keep track of aerial concentrations of pheromone. The results show that the one-component formula disrupts mating as efficiently as the more complete four-component blend at doses applied in this study. This fact improves the prospects for mating disruption of indoor pyralids, since many pyralid species share the major component in their pheromones, and, thus, can probably be controlled simultaneously by using this compound only.

Animals↗
PubMed1987

Influence of stagnation of water pathways on mosquito population density in connection with malaria transmission in the Solomon Islands.

Malaria is the major health problem in the Solomon Islands. The area of Guadalcanal plains has been known as the most malarious area of the Solomons. In spite of well executed DDT indoor spraying, malaria transmission was not interrupted. The causative factors responsible for this persisting transmission appeared to rest on three factors: refractoriness of Anopheles farauti to DDT spraying; the habit of people to stay outside late in the evening and a marked outdoor biting tendency of A. farauti. It was found that DDT indoor spraying alone had little impact on interruption of malaria transmission. This study conducted in early 1974 was planned to observe the change of mosquito population density in relation to the constriction of the river-mouth in north Guadalcanal in order to consider alternative means for malaria control. With the result of this study, one can assume, with a reasonable degree of certainty, that the improvement of the malaria situation in north Guadalcanal would be associated with steady flow of the river water by maintaining the river/stream-mouth in an open condition.

Anopheles↗
PubMed1989

[The effect of cage type and population density on the body weight development of laboratory mice].

The effect of different keeping conditions on body weight gain was studied in 200 male Fzt:DU mice between days 21 and 70 of life. The animals were divided in four different housing groups: DU-B (housing in stress cages), DU-B+HI (housing in stress cages and afterwards in standard cages type HI), DU-HI (housing in standard cages type HI) and DU-S+AP (housing in standard group cages). Housing in stress cages resulted in lower body weight gain at every age; subsequent housing in standard cages type HI for one week failed to compensate this effects. Likewise, keeping of four mice in standard cages type I (DU-HI) between days 42 and 70 of life also resulted in delayed body weight gain. It is possible that the chosen population density was not an optimum for normal weight gain during the adult life. Animals kept in standard stocking cages (DU-S+AP) had the highest body weight gain.

Animals↗
PubMed2004

[Krigle estimation and its simulated sampling of Chilo suppressalis population density].

In order to draw up a rational sampling plan for the larvae population of Chilo suppressalis, an original population and its two derivative populations, random population and sequence population, were sampled and compared with random sampling, gap-range-random sampling, and a new systematic sampling integrated Krigle interpolation and random original position. As for the original population whose distribution was up to aggregative and dependence range in line direction was 115 cm (6.9 units), gap-range-random sampling in line direction was more precise than random sampling. Distinguishing the population pattern correctly is the key to get a better precision. Gap-range-random sampling and random sampling are fit for aggregated population and random population, respectively, but both of them are difficult to apply in practice. Therefore, a new systematic sampling named as Krigle sample (n = 441) was developed to estimate the density of partial sample (partial estimation, n = 441) and population (overall estimation, N = 1500). As for original population, the estimated precision of Krigle sample to partial sample and population was better than that of investigation sample. With the increase of the aggregation intensity of population, Krigel sample was more effective than investigation sample in both partial estimation and overall estimation in the appropriate sampling gap according to the dependence range.

Algorithms↗
PubMed1978

[Relationship between the ganglioside composition of Ehrlich ascitic carcinoma and cell population density].

The ganglioside composition of Ehrlich ascite carcinoma cells changes drastically with changes in density of the cell population. Upon 30-fold dilution of the native cell suspension and subsequent incubation for 2 h the amount of total gangliosides per cell doubles the quantities of a monosialoganglioside and of a disialoganglioside increase ten- and five-fold, respectively, whereas the other cell gangliosides do not change. The decrease of cell density is supposed to be accompanied by induction on the cell surface of a sialytransferase activity, which appears to be depressed in the dense suspension.

Animals↗
PubMed1996

[Phenotypic and genotypic structure of a natural Drosophila population with respect to the reaction of individuals to an increase in population density and its seasonal change].

In spring and summer, the natural population of Drosophila studied exhibited a high level of phenotypic and genotypic heterogeneity with regard to change of individual fertility with an increase of density of adult flies. From spring to autumn, the level of genotypic variation decreased. In autumn, all phenotypic variation resulted from environmental factors. In spring, individuals sensitive to overcrowding, adapted to low density, and highly fertile in low-density conditions prevailed in the population. In summer and autumn, the population was mostly composed of individuals with opposite characteristics. On the basis of the obtained results, a conclusion on operation of cyclic density-dependent selection in the population examined was made. Selection's functional role in control of seasonal population size dynamics is discussed.

Adaptation, Physiological↗