Sequential sampling for evaluation of caterpillars, small and large in soybean

Abstract

Among the main limitations of grain yield in soybean are the insect pests, especially the defoliating caterpillars. It is necessary to reveal and quantify these insects for proper decision-making according to pre-established control levels. So, for the implementation of appropriate management of these soybean insect pests, there is a necessity to establish a sampling plan that will allow an effective, reliable and less time consuming estimation of the population density of pests. This work aims to establish a sequential sampling plan for small and large caterpillars in soybean in accordance with the sequential test of probability rates. Data was collected for two growing seasons (2010/2011 and 2012/2013). The number of small caterpillars ( 1.5 cm) of the species Anticarsia gemmatalis (Hubner, 1818), Chrysodeixis includens (Walker, 1857) and Spodoptera eridania (Cramer, 1872) was estimated using the vertical cloth-to-beat in a grid of 154 sample points marked with a 20 × 20 m spacing in an area of 6.16 ha of soybean. The distribution of small and large caterpillars in soybean is aggregated. According to the sequential sampling plan, the number of maximum samples, for the decision making of the control or not of caterpillars in soybean is 30 samples units. Key words: Pest management, sampling plan, vertical cloth-to-beat, spatial distribution.