The Hertz Corporation

About: The Hertz Corporation is a based out in . It is known for research contribution in the topics: Population & Soil water. The organization has 9562 authors who have published 11044 publications receiving 447929 citations. The organization is also known as: Hertz Rental Car & Hertz Rent-a-Car.

Modelling the dynamic spatio-temporal response of predators to transient prey patches in the field

Abstract: The spatio-temporal dynamics of two aphid species (Metopolophium dirhodum and Sitobion arenae) and a generalist predator (Pterostichus melanarius) were observed in a field-scale study using a grid of 256 sampling locations with a 12-m spacing. Using Spatial Analysis by Distance Indices we demonstrate that populations show ephemeral spatial pattern at the field scale. We observed a positive, lagged beetle response to this aphid pattern; Conversely, the aphids displayed a negative, lagged response to beetle spatial pattern. Examination of the local structure of the spatio-temporal dynamics revealed a strong response by the beetle population to aphid patches. The temporal structure of spatial associations between the species shows a strong correspondence with those from a conceptual model of predator-prey spatial interaction. The spatially coupled dynamics were sufficiently strong for the predator to have a negative effect on the intrinsic rate of increase of their prey.

Challenges with managing insecticide resistance in agricultural pests, exemplisfied by the whitefly Bemisia tabaci

Abstract: For many key agricultural pests, successful management of insecticide resistance depends not only on modifying the way that insecticides are deployed, but also on reducing the total number of treatments applied. Both approaches benefit from a knowledge of the biological characteristics of pests that promote or may retard the development of resistance. For the whitefly Bemisia tabaci (Gennadius), these factors include a haplodiploid breeding system that encourages the rapid selection and fixation of resistance genes, its breeding cycle on a succession of treated or untreated hosts, and its occurrence on and dispersal from high–value crops in greenhouses and glasshouses. These factors, in conjunction with often intensive insecticide use, have led to severe and widespread resistance that now affects several novel as well as conventional control agents. Resistance–management strategies implemented on cotton in Israel, and subsequently in south–western USA, have nonetheless so far succeeded in arresting the resistance treadmill in B. tabaci through a combination of increased chemical diversity, voluntary or mandatory restrictions on the use of key insecticides, and careful integration of chemical control with other pest–management options. In both countries, the most significant achievement has been a dramatic reduction in the number of insecticide treatments applied against whiteflies on cotton, increasing the prospect of sustained use of existing and future insecticides.

The manifold effect of selection.

Abstract: WHEN dissecting females for mating tests it was observed in S—79 that some of them were abnormal in their numbers of spermathec. In Drosophila melanogaster, as indeed in all species of the genus and in most genera of the group Drosophilinee, the normal number of spermathecle in a female is 2 (plate I (a)). Occasional cases of 3 spermathec, or very rarely 4, have been reported in wild-type females of various species. In our own examination of various wild-type strains, obtained from elsewhere or begun from wild flies and maintained in this laboratory for several years, one strain has been found to show as many as 7 per cent, of females with other than 2 spermathec, and another strain has 3 per cent. (table 15). In the remainder of the wild strains abnormalities were either absent or so rare as to be found only when large numbers of flies are dissected. Single examples with 3 spermathec have been found in the Or and Sk stocks, out of 852 and 1382 females respectively. In our strains, as in others reported earlier by Sturtevant (1926), Wexelsen (1928), and Nonidez (1920), the abnormalities lay in the possession of i or 2 spermathec in excess of the normal 2, while occasionally one of the usual 2 spermathec was abnormally large, this being described as 2+ in our notation. Sturtevant and Wexelsen were able to establish lines with a greater frequency of these abnormally high spermatheca numbers, Wexelsen's being indeed a line breeding almost true for 3 spermathec, a condition which Hadorn and Graber (i4) state to be normal in many Diptera. In Wexelsen's flies the extra spermathec were due to the action of genes in at least three of the four chromosomes, but Hadorn and Graber describe a case of extra spermathec, the precise kind and frequency of which depended on the temperature at which the flies

Rapid method for the determination of cation-exchange capacity of calcareous and non-calcareous soils

Abstract: “Compulsive” exchange takes place between a barium-soil and magnesium sulphate solution because Ba2+ ions are removed from solution by precipitation of barium sulphate. This phenomenon provides a basis for the very convenient routine method for cation-exchange capacity determination in soils described here. An EDTA titration is used to measure the amount of magnesium exchanged from a standard solution by a Ba-soil, which enables the cation-exchange capacity to be calculated. Advantages of the method are its speed and that the sample does not have to be washed exhaustively, so avoiding possible hydrolysis. It compares favourably with standard A.O.A.C. procedure and is much more widely applicable. Soils rich in organic matter, e.g., peats, or with much calcium carbonate, can be handled without difficulty.