Organophosphate resistance in olive fruit fly, Bactrocera oleae, populations in Greece and Cyprus

The olive fruit fly Bactrocera oleae (Gmelin) (Diptera: Tephritidae) is the most important pest of olives in countries around the Mediterranean basin. Its control has been based mostly on bait sprays with organophosphate insecticides (usually dimethoate or fenthion) for about 40 years. In the present study, the resistance status of olive fruit fly populations to dimethoate was examined in Greece and Cyprus over 2 years. Thirty-one populations from various regions of Greece, nine from Cyprus and one laboratory susceptible strain, which served as a control, were assayed by topical application of dimethoate. Considerable variation in the resistance levels to dimethoate was recorded in the populations of B. oleae, with resistance ratios ranging from 6.3 to 64.4 (ED50 values 12.5-128.7 ng dimethoate per insect). The highest resistance ratios were found in populations from Crete, and the lowest in those from Cyprus. This variation could be attributed to different selection pressures from insecticidal applications among populations from the various regions. Migration of resistant genotypes, either autonomous or via commerce, may also be involved. © 2006 Society of Chemical Industry

Effect of temperature on development, growth and feeding of Coccinella septempunctata and Hippodamia convergens reared on the tobacco aphid, Myzus persicae nicotianae

Preimaginal development, mortality, aphid consumption rate, and size and weight upon reaching the adult stage of the aphidophagous coccinellids Hippodamia convergens Guerin-Meneville and Coccinella septempunctata L. collected from Karditsa, central Greece, were examined at four constant temperatures ( 14, 17, 20 and 23 degrees C) and L16: D8. The coccinellids fed on the tobacco aphid, Myzus persicae nicotianae Blackman. Egg, larval and pupal mortality was highest at 14 degrees C reaching 85.0, 73.8 and 29.4% in H. convergens and 49.3, 75.4 and 58.8% in C. septempunctata, respectively. Total preimaginal development ranged from 57.2 to 70.4 days at 14 degrees C, and to 16.9 and 22.1 days at 23 degrees C in H. convergens and C. septempunctata, respectively. Heavier and larger adults of H. convergens were obtained at 17 and 20 degrees C. In C. septempunctata temperature did not affect adult weight while the lowest size was observed at 14 and 17 degrees C. Day-degrees requirements for preimaginal development in H. corvengens were 212.9 above a developmental threshold of 11.0 degrees C. The corresponding values for C. septempunctata were 281.5 and 10.7 degrees C. In H. convergens total and daily aphid consumption ranged from 46.8 aphids at 14 degrees C to 85.0 aphids at 23 degrees C and from 1.5 aphids at 14 degrees C to 9.2 aphids at 23 degrees C, respectively. The corresponding values for C. septempunctata were 112.0 and 2.7 at 14 degrees C and 157.7 and 12.4 at 23 degrees C. The results show the high potential of both predators as biological control agents against the tobacco aphid. The knowledge obtained could be essential for their appropriate use and for the improvement of mass rearing systems

Contact and code-switching

Book synopsis: Language contact is a dynamic area of contemporary linguistic research that studies how language changes when speakers of different languages interact. Accessibly structured into three sections, The Handbook of Language Contact explores the role of contact studies within the field of linguistics, the value of contact studies for language change research, and the relevance of language contact for sociolinguistics. This authoritative volume presents original findings and fresh research directions from an international team of prominent experts. Thirty-seven specially-commissioned chapters cover a broad range of topics and case studies of contact from around the world