THE HORIZONTAL AND VERTICAL DISTRIBUTION OF EMPOASCA KRAEMERI (ROSS AND MOORE) IN BEAN FIELDS (PHASEOLUS VULGARIS L), THE POPULATION DYNAMICS AND RECOMMENDATIONS FOR THE MONITORING IN THE FIELD UNDER TROPICAL CONDITIONS [German]

摘要

Considering three cultivation periods and three cultivars, studies of spatial distribution of Empoasca kraemeri (Ross and Moore) within bean fields were carried out. The sampling scheme includes 10 bean plants in each plot, finding our the abundance of the individuals on each of the existing leaf. Sampling was done every 2 or 4 days until a plant age of 60 days. To evaluate the horizontal and vertical distribution of E. kraemeri, the indices of ''Mean Crowding'' and ''Patchiness'' were calculated. The influence of population density on the ,,Mean Crowding''-index was estimated by ''patchiness regression The presence of the cicada within the field shows a random horizontal distribution pattern, whereas the individuals were aggregated on single leaves of the plant (vertical distribution). In most of the cases, the individuals were unimodal distributed on the plant. Changes in the numerical order of the leaf on which the cicada were most abundant within the vegetation period, could be described using a ,,linear regression model with unknown breakpoint''. Until approximately 33 days, there were only negligible changes. After this time, the most colonized leaf 3 (y) can be determined using the function (y) over cap = -12,64 + 0,47x (x: days after seed). The sample unit should include five leaves per plant, grouped near the most populated leaf. On the other hand, the sampling locations within the field should be selected randomly.