Decision-making for thrips control in soybean fields using precision agriculture principles

In precision agriculture, sub-areas of fields with similar features are called management zones and the inputs applied similarly in these zones. Such notion of management zones is applicable to high-output soybean fields where thrips are an emerging problem leading to losses up to 15%. Management zones are an agricultural management strategy that can be used for decision-making for controlling thrips on soybean fields. Thus, a 2-year study was carried out on commercial soybean fields aimed at developing a decision-making system for controlling soybean thrips using management zones. Three control programmes were established and assessed: Cl-conventional control with insecticide use in the entire field; IPM-CS-conventional sampling plan + spray upon reaching the economic injury level (EIL; 3.43 thrips/sample); and IPM-MZ-spraying only specific areas of the field where thrips density reached the EIL. The decision to control reached using the IPM-CS and IPM-MZ programmes was 3x lower than those of the CI, which incurred in 75% mode decision mistakes. Furthermore, the decision to spray insecticides based on analysis of data for Cl was also incorrect. In 8.5% (3.6% of treated and 4.9% of non-treated) of the field, the decisions of the IPM-CS programme were incorrect. The total cost of the Cl programme (US$ 11.4/ha) was higher than that of the IPM-CS and IPM-MZ programmes (US$ 3.2 ha(-1)). Therefore, owing to its technical, economic, and environmental advantages, the establishment of management zones seems worthy of incorporation in integrated thrips management decision-making systems for soybean fields.