The application of supplemental blue light in greenhouse chrysanthemum production is part of a biological control strategy to enhance reproduction of Orius insidiosus Say, a natural predator of the western flower thrips, Frankliniella occidentalis Pergande. Two greenhouse experiments were conducted to determine the influence of a blue light—supplemented long day on flowering and vegetative growth in three cultivars of the short-day plant Dendranthema ×grandiflora (Ramat.) Kitamura. In Expt. 1, two cut chrysanthemum cultivars (`Manatee Iceberg' and `Naples') were exposed to: a) 9-hour ambient light and 15-hour artificial blue-biased (400-500 nm) light at two blue light intensities (3.6 or 7.0 μmol·m-2·s-1); b) 9-hour ambient light and 15-hour artificial broad spectrum light at a broad spectrum intensity of 3.6 μmol·m-2·s-1; c) 9-hour ambient light maintained with black cloth; or d) an ambient short day. Under a continuous photoperiod, flower initiation in both cultivars in the lower intensity blue light was not significantly different from that in short-day regimes. However, in both blue light intensities, flower size and dry mass were significantly less than in the short-day regimes. Increasing the dose of blue light decreased flower dry mass in `Naples' by 60% and in `Manatee Iceberg' by 72%. Plants were shorter with less vegetative mass in the short-day regimes. In Expt. 2, `Naples' and the pot chrysanthemum `Boaldi' were exposed to a) 9-hour ambient light and 6-hour artificial blue-biased (400-500 nm) light at four blue light intensities (0.4, 0.7, 1.6, or 3.5 μmol·m-2·s-1); b) 9-h ambient light maintained with black cloth; or c) an ambient long day. For both cultivars, in all blue light regimes, neither flower dry mass nor vegetative dry mass differed significantly from those in the short-day regime. The results indicate that exposing D. grandiflora to a blue light—supplemented long day at blue light intensities <3.5 μmol·m-2·s-1 does not adversely affect flower initiation and development.

A mail survey of greenhouse growers was conducted in 1994 and 1995 to determine the presence and importance of western flower thrips (WFT), Frankliniella occidentalis Pergande, in Maine greenhouses in growing years 1993 and 1994. Respondents were licensed growers with at least 1000 ft 2 (93 m 2 ) of greenhouse growing area. The survey objectives were to develop a grower demographic profile; determine the incidence of WFT and two WFT-vectored plant viruses, tomato spotted wilt (TSWV) and impatiens necrotic spot (INSV); and identify current WFT management strategies. The survey shows that Maine greenhouse growers are seasonal, experienced and retail oriented. Their growing area averages less than 10,000 ft 2 (929 m 2 ) and they produce a diverse crop mix and choose to import production stock as much as propagate it themselves. Both WFT and TSWV/INSV have increased in severity in Maine greenhouses over the past 10 years. Larger, year-round greenhouses are more likely to experience infestations of WFT and higher virus incidence. An integrated pest management (IPM) strategy is employed by the majority of growers surveyed. Insecticide application is the primary tactic used to control WFT. Fewer than 4% of the growers use natural enemies to control thrips. However, 63% responded that future research in pest management should focus on biological control.

An important limitation in using the insidious flower bug,Orius insidiosus(Say) (Hemiptera: Anthocoridae), as a biological control agent in north temperate winter greenhouse crop production is its tendency to enter reproductive diapause during short photoperiods. Laboratory experiments assessed the effect of a blue light-supplemented short photoperiod over a range of temperature regimes on female reproductive diapause induction, nymph development and survival, ovarian maturation period, and oviposition ofO. insidiosus.In experiment one, allO. insidiosuslife stages were exposed to a broad-spectrum photoperiod of 15:9 (L:D) h, a blue light-supplemented photoperiod of 9:15 (L:D) h, consisting of 9 h broad-spectrum light followed by 6 h blue light, or a broad-spectrum photoperiod of 9:15 (L:D) h, all at 24 ± 1°C. Approximately 75% of mated females reproduced in the broad-spectrum long photoperiod and the blue light-supplemented short photoperiod regimes, whereas over 50% of the bugs diapaused in the broad-spectrum short photoperiod regime. There was no difference among the light treatments for all other measured responses. In experiment two, allO. insidiosuslife stages were exposed to the blue light supplemented short photoperiod over a range of temperature regimes (19–28°C). At least 90% of mated females reproduced at each temperature. A linear rela tionship occurred for temperature and nymph development and for temperature and ovarian maturation period. The oviposition rate was similar at 22°, 25°, and 28°C. This study indicates the potential for using supplemental blue light to enhanceO. insidiosusreproduction in a short photoperiod and may be important as a biological control strategy in winter greenhouse production systems.