Abstract
A tobacco field in Greece was sampled during the 2001 and 2002 growing seasons to assess the seasonal trends in densi- ties and spatial distributions of the aphid Myzus persicae (Sulzer) and its predatory mirid Macrolophus costalis (Fieber). On repeated occasions between June (just after the transplantation) and September (just before harvest), 20 tobacco leaves (10 from the upper and 10 from the lower plant part) were taken from randomly chosen plants. These leaves were sampled for aphids and mirids. In both years, the highest aphid densities were recorded during July and August, while aphid numbers were low in September. In contrast, the majority of M. costalis individuals were found during September when aphid numbers were low. Significantly more M. persicae individuals were found in the upper part of the plants, whereas significantly more M. costalis individuals were found in the lower part of the plants. As indicated by Taylor's Power Law estimates, both species were aggregated in their spatial distributions among sampling units (leaves). Wilson and Room's model, based on the Taylor's estimates, was used to calculate the mean number of aphids and mirids, from the proportion of sampling units (leaves) that had > 0 individuals of each species. This model provided a sat- isfactory fit of the data for both the aphid and the mirid. In addition, Wilson and Room's model was successfully used to predict the mean number of aphids and mirids in a series of samples that were carried out in the same area between June and September 2003 for model validation. Finally, equations are given for the calculation of precision in estimating the mean number of aphids or mirids per sampling unit, and the required sample size for a given level of precision.
Highlights
Myzus persicae (Sulzer) is the main aphid pest infesting tobacco in Greece (Kavallieratos et al, 2004)
According to the results of our study, under the conditions prevailing in the study area, high aphid densities are established in tobacco fields during July, approximately 20–30 days after the transplantation of the plants
The abundance of M. costalis was continuously low during the summer months, and its densities increased only during September, when M. persicae densities were low
Summary
Myzus persicae (Sulzer) is the main aphid pest infesting tobacco in Greece (Kavallieratos et al, 2004). A mirid, Macrolophus costalis (Fieber), is a predator of M. persicae on tobacco (Dimitrov, 1977; Athanassiou et al, 2003) that can develop high population densities (Athanassiou et al, 2003). This predator is considered one of the most abundant predatory species in tobacco fields (Dimitrov, 1977; Athanassiou et al, 2003). We test the value of M. costalis as a biocontrol agent in the field against M. persicae
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