Evaluation of the efficiency of various medfly female trapping combinations in Costa Rica in support of the sterile insect technique

This report contains information from a four-year research programme co-ordinated by the International Atomic Energy Agency. The objective of the programme was to develop a trapping system for females of the Mediterranean fruit fly (medfly), Ceratitis capitata (Diptera: Tephritidae), for practical use in Sterile Insect Technique (SIT) programs and to design and evaluate a trap to obtain eggs from wild female medflies in order to estimate sterility induction in the field population. The study was carried out at two different Agricultural Research Stations of the University of Costa Rica, the Fabio Baudrit Agricultural Research Station (FBS) and Laguna de Fraijanes Agricultural Research Station (LFS), and in a privately-owned coffee and orange plantation in Grecia canton (Coope-Victoria Farm). Female medfly attractants tested were three food based 'female' attractants (FA-3), namely ammonium acetate (AA), 1,4 diaminobutane (putrescine) and trimethylamine, all formulated to last at least one month. These attractants were evaluated either in combinations of two (AA + putrescine, termed FA-2) or all three (termed FA-3). The attractants were tested in various traps including the plastic International Pheromone's McPhail traps (IPMT) and Tephri traps, a Spanish trap similar to the IPMT. Traps were used either as a dry trap (provided with DDVP) or a wet trap (provided with water and 0.01% surfactant). Jackson traps with Trimedlure (JT,TML), a routinely used male medfly trapping system, was also used. Trapping experiments conducted in the citrus plantation of the FBS resulted in the following fly/trap/day indices (F/T/D): 7.18 with JT,TML; 4.62 with open bottom dry traps (OBDT) baited with FA-3; 4.18 with OBDT (PVC) baited with FA-3; 7.73 with IPMT baited with FA-3, wet; 8.245 with IPMT baited with FA-3, dry; 5.27 with IPMT baited with NuLure; 4.79 with Tephri baited with FA-3, wet; and 5.42 with Tephri, FA-3, dry. The F/T/D indices at the Coope-Victoria Farm, in coffee, were: 14.35 with JT,TML; 8.65 with OBDT, FA-3; 8.15 with OBDT (PVC), FA-3; 10.52 with IPMT, FA-3, wet; 14.95 with IPMT, FA-3, dry; 9.28 with IPMT, NU+B; 13.99 with Tephri,FA-3, wet; and 14.24 with Tephri, FA-3, dry traps. The final results of these experiments showed that the types of traps and female attractants developed and used in these experiences are good tools to capture female medflies and to evaluate changes and dynamics in the wild female medfly populations when releasing males only strains in SIT programmes. These studies showed that dry IPMTs and Tephri traps, with the FA-3 attractants and DDVP, were the most efficient and practical for capturing wild females in sterile males release programmes. (author)