Optimization of Orius majusculus release: photoperiodic sensitivity at different temperatures and storage of diapausing adults

Authors: ŞERİFE ÜNAL BAHŞİ, İRFAN TUNÇ

Abstract: The photoperiodic sensitivity and storage of Orius majusculus (Reuter) from Antalya was investigated to obtain data for the optimization of its release. In the current study, it was not possible to induce a high (up to 100%) incidence of diapause unless all the nymphal instars and adults were successively exposed (i.e. full exposure) to a short day length (11.5 h) at constant temperatures of 18 and 26 °C, and fluctuating temperatures of 10/26 °C. Hence an intermittent exposure to long day lengths, even for short periods of time (only during instars IV–V or adult stage), would avoid a high incidence of diapause at 10/26 °C and 26 °C. The response of O. majusculus nymphal instars and adults to a short day length with a low incidence of diapause under fluctuating temperatures suggests that greenhouses, where such temperatures prevail, provide an environment that is conducive to diapause prevention. The release of adults is a better approach than the release of nymphs, since the adults and their nymphs, until the eclosion of new adults, are expected to respond to short day lengths with a low incidence of diapause in greenhouses. When nymphs are released, on the other hand, a high incidence of diapause would be inevitable. Increasing the constant temperature to 30 °C at full exposure did not prevent diapause and consequently did not change the incidence of diapause. Storage of diapausing O. majusculus adults was possible for 1 month with a higher survival rate and fecundity than in a study based on the storage of nondiapausing adults at a lower temperature.

Keywords: Biological control, diapause, Frankliniella occidentalis, Orius majusculus, photoperiodic sensitivity, storage

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