Modelling population dynamics of Orius laevigatus and O. albidipennis (Hemiptera: Anthocoridae) to optimize their use as biological control agents of Frankliniella occidentalis (Thysanoptera: Thripidae).

ORIUS LAEVIGATUS: (Fieber) and O. albidipennis (Reuter) play an important role in the control of Frankliniella occidentalis (Pergande) in crops and natural vegetation in the Mediterranean area. The biological parameters of the two anthocorids were studied and modelled in relation to temperature to optimize their use in thrips control programmes. Development times and reproductive parameters of O. laevigatus and O. albidipennis were determined at 20, 25, 30 and 35 degrees C. Pre-imaginal development times ranged from 34.6 and 37.2 days at 20 degrees C to 12.3 and 10.2 days at 35 degrees C in O. laevigatus and O. albidipennis, respectively. The lower thermal development threshold was significantly higher for O. albidipennis (14.2 +/- 0.9 degrees C) than for O. laevigatus (11.3 +/- 0.7 degrees C). No significant differences in fecundities between the two anthocorids were observed at 20, 25 and 30 degrees C. At 35 degrees C, O. albidipennis had a significantly higher fecundity than O. laevigatus. Non-linear models were used to explain reproduction and female survivorship in relation to temperature. The upper reproductive thresholds were estimated at 40.9 +/- 0.3 and 35.5 +/- 0.1 degrees C for O. albidipennis and O. laevigatus, respectively. The different optimum temperatures may explain, at least in part, the different distributions of the two species in the Palaeartic region and their population dynamics in greenhouses and natural vegetation in the south of Spain. The estimation of rm as a function of temperature showed high variability between years. Three release rates of 0.75-0.25 Orius per plant are recommended from early March to mid May to deal with thrips outbreaks in pepper crops.