Spatial distribution and sequential sampling plan for Diceraeus melacanthus (Hemiptera: Pentatomidae) in maize at the vegetative stage

Abstract

Diceraeus melacanthus has become a key pest of maize in Brazil, primarily during the early vegetative growth stages. This study examined the spatial distribution of D. melacanthus in maize and developed a sequential sampling plan for monitoring the pest in maize at the vegetative stage. The samples were collected from six fields of 1250 m2 each in the second crop seasons of 2012 and 2013. The sampling unit consisted of five randomly chosen plants per plot, which were visually examined for D. melacanthus on a weekly basis, totaling 250 plants evaluated per field on each sampling date. To construct the sampling plan, an economic threshold of 0.8 stink bugs per sample unit (five plants) was adopted. According to the indices of dispersion and by fitting the frequency data to mathematical distributions, the spatial distribution of D. melacanthus in maize is aggregated. From the obtained data, two decision lines were generated, one of which, S1 = 3.5683 + 0.5702 N, recommends taking control action, whereas the other, S0 = −3.5683 + 0.5702 N, suggests that no control action is needed. The sequential sampling plan indicated an expected maximum number of 26 sampling units (∼130 plants) to determine whether to control the pest with prefixed precision level of 95%. This sampling plan may help the decision-making for the control of D. melacanthus in maize, contributing for a sustainable management of this herbivore to increase farmers’ profit.