Controlling Frankliniella bispinosa (Thysanoptera : Thripidae) on Florida citrus during bloom and increased fruit set on navel and 'Valencia' oranges

Four field experiments were conducted during 1995 and 1996 to evaluate incr eased fruit set of navel and 'Valencia' oranges or 'Marsh' grapefruit varie ties by controlling Franhliniella bispinosa (Morgan) (Thysanoptera: Thripid ae) on citrus flowers during bloom. In three experiments, Chlorpyrifos 4EC at 4.68 liters/ha provided 5, 5, and 4 days of effective residual control o f F. bispinosa adults on citrus flowers and 3 or more days at 3.16 liters/h a in the remaining experiment. Corresponding lengths of larval thrips contr ol were 12, 12, and 8 days, respectively. The Chlorpyrifos 4EC treatments a t 3.16 liters/ha applied on 25 March in the fourth experiment provided 11 o r more days of larval thrips control. Use of a single, properly timed insec ticide application between maximum bud swell and full bloom, when F. bispin osa or F. kelliae adults are increasing, will increase fruit set. Preventin g establishment of larval thrips populations appears to be important.