Management of western flower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), in hydroponic strawberry crops: using yellow sticky traps to determine action thresholds

Abstract  The relationship between western flower thrips (WFT) populations in flowers and catches on yellow sticky traps was investigated in a hydroponic strawberry crop in the Sydney area in 1999–2000. The thrips population was initially dominated by males, but by mid-summer it was composed primarily of females. At a point when approximately 60–65% of WFT on traps were female (approximately 20–30 females per trap), the overall density of thrips on traps and in the crop increased rapidly, resulting in severe damage to immature fruit. The sex ratio of 0.60–0.65 females corresponded very closely to a mean of five adult WFT per flower at the start of the trapping week, which was an infestation level previously calculated as the action threshold to prevent damage to young green fruit.