Acaricidal activities of Santolina Africana and Hertia Cheirifolia, two endemic plants of north Africa, on the two spotted spider mite (Tetranychus urticae)

Poster (2011, May)

The two-spotted spider mite, Tetranychus urticae Koch, is a worldwide pest which feeds on a large variety of plant families. Because its resistance to acaricides is spreading rapidly, the development of ... [more ▼]

The two-spotted spider mite, Tetranychus urticae Koch, is a worldwide pest which feeds on a large variety of plant families. Because its resistance to acaricides is spreading rapidly, the development of new biological control tactics for population management is crucial. Plant extracts, such as Santolina africana and Hertia cheirifolia (Asteraceae), may represent viable alternatives, since they are currently considered to be minimumrisk pesticides. Although these two plants are known for their biocidal properties, the extract concentration that provides the most efficient control has not yet been precisely determined. In this study, we conducted a series of laboratory experiments to determine the susceptibility of adult females to different concentrations of S. africana and H. cheirifolia extract. These plants were steam-distilled and sprayed using a Potter spray tower. Mortality and fecundity were measured upon treatment with extract concentrations ranging from 0.07 to 6.75 mg/L. Female mortality increased with concentration, with LD50 values of 2.35 mg/L for S. africana and 3.43 mg/L for H. cheirifolia, respectively Reduced fecundity was previously observed at concentrations of 0.07, 0.09 and 0.29 mg/L .The chemical composition of the two oils were characterised by GC-MS. The most abundant components of the S. africana oil were terpinen-4-ol (44%), α- terpineol (11.31%) and borneol (6.73%). Camphor (15.11%), terpinen-4-ol (14.2%), α- terpineol (9.3%) were characteristic of the Hertia oil. [less ▲]

Contrôle de Tetranychus urticae par les extraits de plantes en vergers d'agrumes

in Entomologie Faunistique = Faunistic Entomology (2011), 63(4), 229-235

Tetranychus urticae est un acarien extrêmement polyphage, reconnu comme un ravageur majeur pour une grande quantité de plantes cultivées. Cet acarien cause d’importants dégâts sur agrumes et ... [more ▼]

Tetranychus urticae est un acarien extrêmement polyphage, reconnu comme un ravageur majeur pour une grande quantité de plantes cultivées. Cet acarien cause d’importants dégâts sur agrumes et principalement sur citronnier, se traduisant par de lourdes pertes économiques. L’objectif de ce travail est de mettre en évidence les propriétés acaricides d'extraits de plantes sur T. urticae. Douze extraits (macérats) issus de 12 plantes et deux acaricides de synthèse (Spirodiclofen et Fenbutatin oxyde) ont été choisis pour les essais en verger de citronniers. Ces résultats montrent que trois macérats extraits d’Allium sativum, A. cepa et Deverra scoparia présentent des propriétés acaricides comparables aux deux acaricides de synthèse qui sont les produits de référence. Cette efficacité perdure jusqu’à plus de 15 jours. Le macérat de D. scoparia a présenté l’activité acaricide la plus toxique et la plus rapide sur la population de T. urticae, 21 jours après traitement par rapport aux autres extraits et par rapport aux produits de référence. Ce travail permettra de mettre en place un programme de lutte intégrée visant le contrôle efficace des tétranyques s’attaquant aux citronniers. Les expériences en verger ont démontré que les extraits végétaux ont un effet acaricide pour T.urticae. [less ▲]

Comparative toxicity of Deverra scoparia essential oil and blends of its major constituents against Tetranychus urticae Koch

Poster (2010, October 14)

The phytophagous two-spotted spider mite Tetranychus urticae Koch is a ubiquitous species, present worlwide on a large variety of plant families. Since T. urticae resistance spread rapidly, biological ... [more ▼]

The phytophagous two-spotted spider mite Tetranychus urticae Koch is a ubiquitous species, present worlwide on a large variety of plant families. Since T. urticae resistance spread rapidly, biological control tactics are crucial to manage spider mite populations. In this respect, plant-derived essential oil products are a good alternative as they are, in general, considered as minimum-risk pesticides. In that context, laboratory experiments were conducted to assess the toxicity of essential oil of Deverra scoparia endemic plant to North Africa on females of the two spotted spider mite T. urticae (Koch). Essential oil was distillated from fresh leaves from D. scoparia and was sprayed on groups of adults females. The susceptibility of these females to D. scoparia essential oil was tested. A series of dilutions were used to bracket the dose-response range. Tests proved that female mortality increased with essential oil concentration with DL50 and DL90 values of 1.79 mg/l and 3.16 mg/l, respectively. The analysis of D. scoparia essential oil using GC-MS revealed presence of 10 major constituents: alpha-thujene, alpha-pinene, sabinene, myrcene, 3-carene, ocimene, terpinene-4-ol, pulegone, eugenol and beta-eudesmol. For a comprehensive evaluation of the potential of D. scoparia essential oil as acaricidal, individual blends activity of these constituents were tested against T. urticae female. Toxicity of blends of different components indicated significant differences among the active and inactive components, with the presence of all constituents necessary to have toxicity near to that of whole D. scoparia oil. The results showed that natural oil of D. scoparia and some of its constituents have potential for development as botanical acaricide, at least against T. urticae. [less ▲]