1 Since the late 1970s, the western flower thrips has spread from its original distribution in western North America to become a major worldwide crop pest. 2 A wide range of data sources have been used to map the original distribution in the U.S.A. and Canada, and the progress of the spread in the U.S.A., Canada, Europe, northern Africa and Australia. 3 The possible reasons for the start of the spread are discussed. The most likely reason is that intensive insecticide use in horticulture in the 1970s and 1980s selected an insecticide resistant strain or strains. These then established in glasshouses across North America and spread from there to Europe, Asia, Africa and Australia. 4 The international spread of the western flower thrips occurred predominantly by the movement of horticultural material, such as cuttings, seedlings and potted plants. Within Europe, an outward spread from the original outbreak in the Netherlands is discernible. The speed of spread was 229 AE 20 km/year. 5 The spread has not been restricted to glasshouses. The western flower thrips has established outdoors in areas with milder winters; for example, across the southern U.S.A., southern Europe and Australia. It also overwinters in some regions with colder winters. 6 Polyphagous phytophagous thrips have many factors predisposing them to become worldwide crop pests, particularly in glasshouses. Some other species that might spread in a similar way to the western flower thrips are listed.

Western flower thrips, Frankliniella occidentalis, first arose as an important invasive pest of many crops during the 1970s–1980s. The tremendous growth in international agricultural trade that developed then fostered the invasiveness of western flower thrips. We examine current knowledge regarding the biology of western flower thrips, with an emphasis on characteristics that contribute to its invasiveness and pest status. Efforts to control this pest and the tospoviruses that it vectors with intensive insecticide applications have been unsuccessful and have created significant problems because of the development of resistance to numerous insecticides and associated outbreaks of secondary pests. We synthesize information on effective integrated management approaches for western flower thrips that have developed through research on its biology, behavior, and ecology. We further highlight emerging topics regarding the species status of western flower thrips, as well as its genetics, biology, and ecology that facilitate its use as a model study organism and will guide development of appropriate management practices.

Two major components have been detected in the headspace volatiles of adult male Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae) that are not present in the headspace volatiles of adult females. The compounds were identified as (R)-lavandulyl acetate and neryl (S)-2-methylbutanoate by comparison with synthetic standards using gas chromatography (GC), GC mass spectrometry (MS), and chiral GC. Field trials were conducted with synthetic compounds in naturally infested crops of sweet pepper grown in large plastic greenhouses in Spain. The catch of adult females and males on blue sticky traps was increased by neryl (S)-2-methylbutanoate alone or by a 1:1 blend of (R)-lavandulyl acetate and neryl (S)-2-methylbutanoate, but (R)-lavandulyl acetate was not active alone. This is the first identification of an aggregation pheromone in the order Thysanoptera. The possible role of (R)-lavandulyl acetate is discussed.

Abstract. 1. This paper analyses catches of flower thrips, grass thrips and predatory flies in water‐traps of seven colours. 2. A correlation is demonstrated between type of host‐plant of thrips and the relative numbers caught by traps of different colours. 3. The literature is reviewed and some general relationships with the effectiveness of different trap colours are hypothesized for: non‐grass foliage insects and their predators and parasites; grass foliage insects; flower‐dwelling insects; predators and parasites not associated with foliage; biting insects; and wood‐borers. 4. This may permit trap colours to be chosen, in particular circumstances, that are ecologically selective for different types of insect.

The western flower thrips Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae) is a cosmopolitan, polyphagous insect pest that causes bronzing to fruit of strawberry (Fragaria x ananassa). The main aim of this study was to test whether mass trapping could reduce damage and to predict whether this approach would be economically viable. In semi-protected strawberry crops, mass trapping of F. occidentalis using blue sticky roller traps reduced adult thrips numbers per flower by 61% and fruit bronzing by 55%. The addition of the F. occidentalis aggregation pheromone, neryl (S)-2-methylbutanoate, to the traps doubled the trap catch, reduced adult thrips numbers per flower by 73% and fruit bronzing by 68%. The factors affecting trapping efficiency through the season are discussed. Damage that would result in downgrading of fruit to a cheaper price occurred when bronzing affected about 10% of the red fruit surface. Cost-benefit analysis using this threshold showed that mass trapping of thrips using blue sticky roller traps can be cost-effective in high-value crops. The addition of blue sticky roller traps to an integrated pest management programme maintained thrips numbers below the damage threshold and increased grower returns by a conservative estimate of £2.2k per hectare. Further work is required to develop the F. occidentalis aggregation pheromone for mass trapping and to determine the best timing for trap deployment. Mass trapping of thrips is likely to be cost-effective in other countries and other high-value crops affected by F. occidentalis damage, such as cucumber and cut flowers.