Spatial distribution and sample size to estimate Euschistus heros population density in wild plants during off-season

Abstract

The neotropical brown stink bug Euschistus heros (F.) is an important pest for many crops in several countries and its ability to survive on associated plants during winter is one of the main factors contributing to the permanence of this insect in crop areas. The objective of this study was to identify the spatial distribution of E. heros, and the minimum number of samples (tussocks of each plant species) required to estimate their population density in wild plants during winter. Field experiments were conducted in 2014, 2015, and 2016. Tussocks of Eustachys retusa, Andropogon bicornis, and Saccharum angustifolium were assessed in the area surrounding the cropped land. Data on the number of E. heros were categorized in plant species and tussock diameter range. The spatial distribution patterns of E. heros were evaluated using different dispersion indexes. To validate these patterns, the data were fitted to probabilistic distribution models. The minimum number of tussock samples required was determined using a statistical model. The results suggest that E. heros has an aggregate distribution in the three plant species evaluated; however, the distribution varies as a function of the tussock size. The numbers of tussock samples to achieve an accuracy within 30% were 146, 87, and 109 for E. retusa, A. bicornis, and S. angustifolium, respectively.