Tunisian Journal of Plant Protection Vol. 8, No. 1, 2013 - Iresa

Regarding contact toxicity, theinsecticide chlorpyriphos-methyl caused100% parasitoid mortality 24 h aftertreatment, but parasitoid mortality fromthe insecticides Prev-Am® orspirotetramat was almost absent. Neitherthe total parasitoid offspring/female northe sex ratio of the progeny wasnegatively affected by Prev-Am® orspirotetramat relative to the untreatedcontrol. According to the IOBCclassification for laboratory trials, bothPrev-Am® and spirotetramat were ratedharmless (IOBC category 1), whereaschlorpyriphos-methyl was categorized asharmful (IOBC category 4) to A. sp. nearpseudococci. None of the insecticidesadversely affected the development of theparasitoid pupal stage inside vinemealybug mummies or the survival of theemerged parasitoids.In laboratory conditions,parasitism of P. ficus and P. citri by theirrespective encyrtid parasitoids A. sp. nearpseudococci and Leptomastix dactylopiiwas negatively affected by the ant T.nigerrimum. Similarly, T. nigerrimumwas shown to significantly disrupt thepredatory activity of Cryptolaemusmontrouzieri larvae when foraging onhost citrus mealybugs. By contrast, thepresence of T. nigerrimum did notnegatively influence the predatorypotential of C. montrouzieri adults whenfeeding on citrus mealybugs.Consequently, the encyrtid parasitoids A.sp. near pseudococci and L. dactylopiiand the larval stage of the predator C.montrouzieri may be considered as T.nigerrimum-sensitive, whereas adults ofC. montrouzieri may be regarded as T.nigerrimum-resistant predators.-----------------Sahraoui, Hajer. 2012. Influence of agro-ecological practices and plantprotection on phytoseiid mites communities in Tunisian citrus orchards.Doctorate Thesis in Plant Protection, joint supervision INAT, University ofCarthage, Tunisia and Montpellier SupAgro, France, 196 pp. (Public Defense:11 December 2012)Mites of the family Phytoseiidae(Mesostigmata) have been extensivelystudied because of the potential of severalspecies as biological control agents ofphytophagous mites and small insect croppests. Phytoseiidae diversity andabundance are known to be mainlyaffected by climate, stability of habitats,food resources and agricultural practices.This study conducted in Tunisian citrusorchards aimed to (i) characterize thediversity of Phytoseiidae in theseagrosystems, (ii) study the effect ofagricultural practices on the diversity andabundance of these species and (ii) studythe effect of weed management strategieson these predatory mites. The resultsobtained allow giving some responses.First, more data are now available onspecies of Phytoseiidae present on citrustrees and associated weeds. Eleven newspecies for the Tunisian fauna have beenfound species of Phytoseiidae, weredifferent according to the species of citrusconsidered and their abundance seemed tobe affected by herbicide sprayings. Onweeds, Phytoseiidae diversity wasdirectly affected by weed diversity.Furthermore, their density was influencedby pesticide sprayings and the weedTunisian Journal of Plant Protection Vol. 8, No. 1, 2013