Martínez Hervás, M.A., Soto, A., & García-Marí, F. 2006 Survey of resistance of the citrus red scale Aonidiella aurantii (Homoptera: Diaspididae) to chlorpyrifos in Spanish citrus orchards.. Bulletin OILB/SROP (Sect. Reg. Ouest Palearctique) 29(3): 255-257.

Notes: [International Conference on Integrated Control in Citrus Fruit Crops. Proceedings of the meeting of the International Organization for Biological and Integrated Control of Noxious Animals and Plants, West Palearctic Regional Section (IOBC/WPRS) Working Group, Lisbon, Portugal, 26-27 September 2005.] California red scale Aonidiella aurantii (Maskell) is an important pest of citrus orchards in Spain. It causes cosmetic damage to the fruit resulting in downgrading in the packinghouses. Several populations of A. aurantii in citrus orchards from Valencia were tested for resistance to the insecticide chlorpyrifos during 2003-2004. All tests were made by bioassays. Fruits infested with first immature stages were dipped for 10 seconds in different concentrations of the chemical between 50 and 20,000 ppm of active ingredient. Mortalities were assessed after 15 days, considering dead those insects that had not developed to the second stage. The estimated CL SUB 50 was used in order to compare the values of susceptibility. The results showed important differences between orchards. Susceptibility was usually correlated with the history of previous treatments made in the plot, with greater degree of resistance in orchards with more previous applications. Some plots showed a high degree of chlorpyrifos resistance, with CL SUB 50 values 250 times higher than those found in the most susceptible plots.