Aggregation pattern, economic injury level, and sampling protocol for Chaetanaphothrips orchidii (Thysanoptera: Thripidae) in citrus orchards

Abstract

Chaetanaphothrips orchidii (Moulton) is an invasive citrus pest in the Mediterranean, which has damaged up to 70% of fruit production. In this study, we aim to calculate its aggregation pattern, develop a sampling plan, and determine its economic injury levels (EIL). For these aims, 10 citrus orchards from Eastern Spain were sampled twice per month between 2018 and 2020, with sampling years varying among orchards. Both larvae and adults of C. orchidii tended to aggregate in fruits in contact with other fruits or leaves, in most orchards and years sampled. Fruit damage percentage increased with thrips occupation during the year. To monitor C. orchidii in citrus, we recommend sampling fruits in contact twice per month from June to October with either enumerative or binomial sampling. The manuscript provides an EIL calculator that considers management cost and revenue specific to each orchard. This tool estimated an EIL of 4.45% of fruit occupied by C. orchidii, for a standard Navel orange orchard sprayed with the maximum allowed concentration of acetamiprid. This sampling protocol and the EIL calculator will allow technicians and growers to decide when and whether an insecticide treatment is required. We expect these efforts to enhance the current integrated pest management program for C. orchidii in citrus orchards.