Population Dynamics of Frankliniella occidentalis Pergande (1895) (Thysanoptera: Thripidae) and Evaluation of its Different Ecotypes and their Evolution in a Rose (Rosa hybrida) Greenhouse in the Sahline Region, Tunisia

摘要

Monitoring population dynamics of Frankliniella occidentalis Pergand (1895) (Thysanoptera; Thripidae) employing blue sticky traps and the weekly collection of flowers allowed the determination of the critical periods of insect population increase in Tunisia, namely spring and early summer. Indeed, the maximum F. occidentalis population was recorded during June, while the lowest number of thrips was observed during winter. On the other hand, the observations revealed that the number of males decreasedgradually compared to females mainly in summer with a proportional decrease in the sex ratio. On the other hand, a study of the occurrence of natural enemies associated with Californian thrips led to the identification of a predatory bug Orius insidiosus Say (1832) (Heteroptera: Anthocorridae) which was frequently observed in the sampled flowers. This predator declined F occidentalis population 5 weeks after its natural introduction and installation into the rose crop greenhouse. Moreover, regular prospecting realized on 2007 in rose crop greenhouses in the Sahline region in Tunisia permitted to distinguish different ecotypes of western flower thrips Frankliniella occidentalis Pergand (1895) (Thysanoptera, Thripidae). Indeed, based on their color, three ecotypes were found: dark, pale yellow and intermediate color. The temporal evolution of these three ecotypes was studied depending on environmental conditions. In fact, the dark ecotype was shown to be mostly abundant during winter and spring and todecrease in summer but did not disappear. However, the pale yellow ecotype was completely absent during the cold season, appeared in spring and summer and dominated the western flower thrips population. The ecotype of intermediate color was present throughout the year without showing too much variation.