The western flower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), is an invasive species and currently occurs in only a few areas in China. An easy, accurate and developmental‐stage independent method to identify F. occidentalis would be a valuable tool to facilitate pest management decision making and, more importantly, to provide an early warning so actions can be taken to prevent its introduction into non‐infested areas. Morphological identification of thrips adults and, to a lesser extent, of second‐stage larvae is the main method currently available to identify F. occidentalis. Molecular identification, however, can be easily carried out by a non‐thrips‐specialist with a little training. In this study, DNA sequence data [within the mitochondrial cytochrome oxidase I gene (COI)] and polymerase chain reaction (PCR) were utilized to develop a molecular diagnostic marker for F. occidentalis. A primer set and PCR cycling parameters were designed for the amplification of a single marker fragment (340 bp) of F. occidentalis COI mtDNA. Specificity tests performed on 28 thrips species, efficacy tests performed on five immature developmental stages as well as on male and female adults and tests on primer sensitivity all demonstrated the diagnostic utility of this marker. Furthermore, the primer set was tested on seventeen F. occidentalis populations from different countries and invaded areas in China and proved to be applicable for all geographic populations. It was used successfully to clarify the distribution of F. occidentalis in the Beijing metro area. These results suggested that this diagnostic PCR assay provides a quick, simple and reliable molecular technique for the identification of F. occidentalis.

Bemisia tabaci (Gennadius) MEAM1 (Hemiptera: Aleyrodidae) and Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), two important invasive species, are serious agricultural pests. In this study, a one‐step, single tube, duplex polymerase chain reaction (PCR) procedure was developed to allow rapid, specific, and sensitive identification of B. tabaci MEAM1 and F. occidentalis in predator guts. The system and conditions used for the duplex PCR were optimized. The species specificity of the duplex PCR determined by comparison against non‐targets that might interact with B. tabaci MEAM1 and F. occidentalis showed that oligonucleotide primers amplified nuclear gene target sequences present only in B. tabaci MEAM1 or F. occidentalis. The limits of detection were 9.53 ng μl−1 for B. tabaci MEAM1 and 8.94 ng μl−1 for F. occidentalis. Within a field cage study, in which predators Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae) and Orius sauteri (Poppius) (Hemiptera: Anthocoridae) were allowed to feed on B. tabaci MEAM1 and F. occidentalis for 10 h, the B. tabaci MEAM1 DNA was detectable in 100% of H. axyridis and O. sauteri, and F. occidentalis DNA was detectable in 80% of H. axyridis and 90% of O. sauteri; this implicated that B. tabaci MEAM1 and F. occidentalis remains could be detected in native predator guts simultaneously. The accuracy and reliability of the assay suggested strongly that the duplex PCR optimized for B. tabaci MEAM1 and F. occidentalis is sensitive and specific for both invasive insects and is therefore useful in early diagnosis and monitoring of B. tabaci MEAM1 and F. occidentalis infections, and can be used to identify domestic predator species and food web relationships.