Susceptibility of Ceratitis capitata Field and Laboratory Strains to Malathion and Spinosad in Tunisia
Susceptibility of Ceratitis capitata Field and Laboratory Strains to Malathion and Spinosad in Tunisia
Meriem Msaad Guerfali1,*, Heitham Hamden1, Salma Fadhl1, Wafa Djobbi1, Lotfi Sillini1, Wafa Marzouki1 and Mohammed Ammar2
ABSTRACT
The Mediterranean fruit fly (medfly), Ceratitis capitata, is a major problem for fruit production in Tunisia. Ceratitis was for long time treated with malathion as main conventional control method. Malathion upon repeated and prolonged use may cause resistance. In an attempt to reduce the insecticide residues in fruit, the government is trying to introduce the application of spinosad that was also reported to cause resistance under extensive use. The aim of this work was to monitor the susceptibility to malathion after prolonged use in wild caught tunisian Ceratitis as well as to spinosad after a survey carried out with farmers and to give precise informations about treatment management state. Surveys and sampling of the wild strain of Ceratitis capitata were conducted in several regions to learn about the nature and number of treatments. The samples were subjected to ingestion toxicity bioassays of malathion and spinosad at different concentrations. Histopathological effects of spinosad were also studied and showed that for doses up to LC50, annoying effects begin to appear in glial and neurosecretory cells. The LC50 for malathion was 75.61 ppm for the populations treated more than 6 times. Low levels of resistance are suspected and should be confirmed by molecular analyses for malathion. On the other hand, spinosad LC50 were 127.95 ppm and 22 ppm for field and laboratory population, respectively. Resistance phenomenon is suspected, a rotation of insecticides with different modes of action is desirable in insect resistance management programs.
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