engleski

Pherocon AM Trapping and the "Whole Plant Count" Method : A Comparison of Two Sampling Techniques to Estimate the WCR Adult Densities in Central Europe

Pherocon AM (PhAM) trapping and visual counting are two commonly used methods for identifying corn fields in the USA that contain a sufficient number of adult western corn rootworms (WCR) to have a detrimental economic impact. The goals of this study were (1) to compare, in Croatia and Serbia, the adult WCR data obtained by both PhAM trapping and the “whole plant count” method, (2) to establish the extent to which the “whole plant count” method could be used as a substitution for PhAM trapping, and (3) to establish the time period in which the data obtained by both methods show the highest correlation. The sampling was conducted in 2006 in 38 fields in Croatia and 22 fields in Serbia. Three to six PhAM traps were placed in each 0.5 to 4 ha corn field. In Croatia, traps were placed in the fields on July 15, when maize in the majority of the fields was between the R61 and R65 developmental stage (according to the BBCH). The traps were inspected every two weeks for a total of three inspections. In Serbia, traps were placed in the fields on July 27, when maize in the majority of the maize fields was between the R65 and R69 developmental stage (according to the BBCH). The traps were inspected once, on August 4, when the maize reached the R69-71 developmental stage. Visual counts were conducted on the same days as the trap inspections. Adult densities in the PhAM traps were correlated to adult densities on the whole plant. Statistical analyses comparing the results of PhAM trapping with the visual “whole plant count” method showed that there is a significant medium to strong correlation between them Correlation coefficients varied depending on the data used in the analysis. According to these results, 1 visually determined adult/plant corresponds to 40 adults/trap/week in Croatia and 50 adults/trap/week in Serbia. This means that both methods are equally useful for estimating the population densities of WCR in the Central European region. When sampling was conducted in the first half of August (corresponding to maize developmental stages R 69-77) the coefficients of determination were the highest [r2(Serbia)=0.753 ; r2(Croatia)=0.4984]. Therefore, the most appropriate period for sampling is during the first half of August. At that time, the majority of the maize plants were between the R69 and R77 developmental stages according to the BBCH scale.

correlation; Central Europe; sampling techniques; Pherocon AM traps; the whole plant count; western corn rootworm

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