TOXICITY OF INSECTICIDE-TREATED SPHERES TO CARIBBEAN FRUIT FLY , ANASTREPHA SUSPENSA AND MEDITERRANEAN FRUIT FLY , CERATITIS CAPITATA ( DIPTERA : TEPHRITIDAE )

The Caribbean fruit fly (CFF), Anastrepha suspensa (Loew) , and the Mediterranean fruit fly (MFF), Ceratitis capitata (Wiedemann), are major tephritid pests that attack a wide range of tropical and subtropical plants. The potential for establishment of these fruit fly species in major U.S. fruitproducing areas (i.e., California, Florida and Texas) has demanded the need for the development of effective reducedrisk pest management tactics to control these flies without the use of broad-spectrum toxic insecticide sprays. In laboratory studies, we evaluated the use of toxic bait stations for control of A. suspensa and C. capitata. Flies were exposed to five treatments in no-choice tests and evaluated at 2, 4, 24, 48 and 72 hours. Treatments included: 1) a new sphere design treated with 1% Spinosad, 2) an old sphere design treated with 1% Spinosad, 3) old sphere design treated with 2% imidacloprid, 4) an untreated new sphere design (control), 5) an untreated old sphere design (control). Experimental design was completely randomized block with 6 and 5 replicates for CFF and MFF, respectively. During the first 24 hours, the only treatment that significantly reduced the survival A. suspensa below the control was the old sphere design with 2% imidacloprid. However, at 48 and 72 hours, respectively, significantly more A. suspensa survived in both controls compared with other treatments. There were no significant differences at 48 and 72 hours between any of the insecticide-treated spheres. Similar results were recorded for C. capitata . The results indicate the potential for using our new sphere design treated with 1% Spinosad for controlling A. suspensa and C. capitata. In Florida, the ever present Caribbean fruit fly (CFF), Anastrepha suspensa (Loew), and the occasional invasive Mediterranean fruit fly (MFF), Ceratitis capitata (Wiedemann), have become serious pests of many tropical and subtropical fruits (Weems, 1967). To protect fruit producing areas in the U.S. and abroad, rigid agricultural quarantines have been established (Anonymous, 1992). Various post-harvest treatments must be adopted as sanitary control measures prior to the export of fruits and vegetables. This might include baitsprays, vapor heat, hot air or hot water immersion, followed by cold storage or methyl bromide fumigation of a limited range of citrus varieties (Sharp, 1993). Pre-harvest strategies are also approved and are included in the “Fly Free Zone” concept (Simpson, 1993). In addition to infesting commercial plantings, fruit flies are typically present in wild and residential plants (Norrbom and Kim, 1988), and commercial control in these environments has generated extreme concern (Headrick and Goeden, 1996). The typical means of eradicating invasive fruit fly populations involve repeated aerial applications of broad-spectrum bait-sprays followed by the release of sterile males (Sterile Insect Technique = SIT). These strategies have garnished criticism from urban populations and conservationists concerned with the effects of broad-spectrum insecticides on non-target organisms (Clark et al., 1996). A potential alternative to the application of broad-spectrum insecticides in residential areas would be the deployment of an attractand-kill device where fruit flies would either come into contact with or be attracted to a sucrose/bait/toxin combination (bait station) (Liburd et al., 1999, 2004). The concept of bait stations for tephritid fruit fly control including, Bactrocera spp. , Rhagoletis pomonella (Walsh) and Toxotrypana curvicauda Gerstaecker is not new (Aluja, 1996; Landolt et al., 1988; Prokopy, 1975; Sivinski and Calkins, 1986). More recently, Liburd et al. (2004) demonstrated the potential use of imidacloprid-treated spheres for control of A. suspensa in areas where it may be difficult to apply broadspectrum insecticides. However, prior to field testing imidacloprid-treated spheres, the pesticide manufacturer elected not to pursue licensing for use in citrus. Consequently, we selected a bio-pesticide, Spinosad (SpinTor 2SC) (Dow Agro Sciences, Indianapolis, Ind.) formulated from a naturally occurring soil bacterium, Saccharopolyspora spinosad , as the toxicant for our bait station study against A. suspensa and C. capitata . The authors chose this bio-pesticide based on its environmental/safety attributes (Thompson et al., 1999). Also, Spinosad efficacy against A. suspensa and C. capitata has been previously demonstrated in laboratory and field tests with little or no effects on the parasitoids of either species (Burns et al., 2001; King and Hennessey, 1996). Spinosad is presently registered for use in aerial application over commercial citrus but not approved to be applied aerially over residential areas. Materials and Methods Experiments to evaluate the toxicity of insecticide-treated spheres to control A. suspensa and C . capitata were conducted in the Small Fruits and Vegetable Integrated Pest Management Laboratory, University of Florida, Gainesville, Fla. A total of five sphere treatments were evaluated. Treatments *Corresponding author; e-mail: oeliburd@ifas.ufl. edu