Conventional sampling plan for thrips in tropical soybean fields

Abstract

Soybean (Glycine max) is the world's most cultivated legume. In recent years, the thrips Caliothrips phaseoli and Frankliniella schultzei (Thysanoptera: Thripidae) have caused >15% yield reduction in soybean crops. Conventional sampling plans serve as the starting point for the establishment of decision-making systems for integrated pest management (IPM) programs. These plans establish the sampling methodology, the number of samples, and the time and cost required. They must be simple, representative, accurate, fast, inexpensive, and suitable for different field sizes and plant growth stages. The objective of this research was to determine a conventional sampling plan to facilitate IPM of thrips in soybean crops. For this purpose, a 2-year study in 29 commercial soybean fields was performed to determined the best sampling technique, the optimal number of samples, and the time and cost requirements for fields of different sizes. Our sampling plan can be used for fields of different sizes, plants of different growth stages, and thrips infestations of different densities. It involves beating the apical part of 40 soybean plants per field on a white plastic tray. The time and cost of sampling ranged from 21 min and US $0.78 (1-ha fields) to 129 min and US $4.78 (100-ha fields). This sampling plan is feasible for incorporation into IPM programs because it is representative, accurate, fast, and inexpensive.