Standardized sampling plan for common blossom thrips management in melon fields from north Brazil

Abstract

Common blossom thrips, Frankliniella schultzei (Thysanoptera: Thripidae), is one of the major pests of melon (Cucumis melo L.), causing yield losses of up to 40%. Frankliniella schultzei is widely distributed in the world, especially in tropical and subtropical regions. Sampling plans are one of the pillars of integrated pest management (IPM) programs. Despite the economic importance of F. schultzei, to our best knowledge, this is the first study to establish a standardized sampling plan for this pest in melon fields. Studies were conducted in 23 commercial melon fields during two years to determine the appropriate sampling system (sample unit, method and sampling size). For all plant growth stages (vegetative, flowering and fruiting), the apex (first) leaf of melon branches was the ideal sampling unit, and direct counting of thrips was the most suitable method for F. schultzei monitoring. The sampling size was calculated using the formula described for the negative binomial distribution (the prevailing frequency distribution) and applying error levels of up to 25%. With one sample consisting of counting the number of F. schultzei on the apex leaf of one branch (randomly selected) on one plant at the 20% error, 70 samples were required, providing the best cost-precision relationship. For varying field sizes (1- to 20-ha melon fields), total sampling time ranged from 25 to 59 min, costing USD 0.83 and USD 1.90, respectively. The developed sampling plan is reliable and should be easy to implement in IPM programs in melon fields under varying crop systems (different field sizes and plant stages) in north Brazil.