Tephritid Fruit Fly Pests in Croatia: an Overview of Damage and Current Control Strategies
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Proceedings of 6th International Fruit Fly Symposium 6–10 May 2002, Stellenbosch, South Africa pp. 325–329 Tephritid fruit fly pests in Croatia: an overview of damage and current control strategies M. Bjelis*4 & V. Pelicaric' Institute for Plant Protection in Agriculture and Foresty, Zvonimirova 14 A, 21210 Solin, Republic of Croatia Trap monitoring and fruit sampling were carried out to determine the pest status and distribution of Mediterranean fruit fly (Medfly), Ceratitis capitata, and olive fly, Bactrocera oleae, from June to November 2001 in Croatia. Results showed an increase in the distribution and economic impor- tance of C. capitata, particularly in citrus-production areas. This species was found in all fruit- production areas, with the exception of the county of Zadar. B. oleae was present in all olive- production areas and was more abundant on the mainland. Management recommendations for both species based on the survey results are discussed. INTRODUCTION fruit pest. This pest is managed by cover spraying Three economically significant tephritid fruit fly the entire tree with organophosphate insecticides, species occur in the littoral and insular regions of by bait spraying with a mixture of protein and Croatia: the olive fly, Bactrocera oleae Gmelin, the organophosphate insecticide, or is not managed Mediterranean fruit fly, Ceratitis capitata (Wiede- at all. Research has been carried out during the mann), and the cherry fruit fly, Rhagoletis cerasi last few decades on new control methods such as Loew. The most numerous and commonly culti- mass-trapping, and testing of natural insecticides, vated fruit species are hosts and include olive,Olea repellants and ready-made baits (Brnetic1989;' europea; grape, Vitis vinifera; mandarin, Citrus Pelicaric' & Bjelis 2002; Bjelis4 & Pelicaric' 2002b). reticulata; fig, Ficus carica, peach, Prunus persica; Ceratitis capitata has been present in the sweet cherry, Prunus avium; sour cherry, Prunus Croatian littoral regions for over 50 years (Kova- cerasus, and apricot, Prunus armeniaca. Less com- cevic4 ' 1960) (Fig. 1). It is becoming an increas- mon hosts include loquat, Eriobotrya japonica; ingly important pest in the region of Dalmatia persimmon, Diospyros kaki; pear, Pyrus comunis; (Bjelis4 & Pelicaric' 2002a), particularly in citrus and apple, Malus domestica. production. This pest was not managed in the Bactrocera oleae is the most significant olive past. Education of fruit growers on plant quaran- *To whom correspondence should be addressed. tine measures has been carried out to minimize E-mail: [email protected] crop losses and reduce Medfly expansion into Fig. 1. Historical distribution of Ceratitis capitata in Croatia. 326 Proceedings of the 6th International Fruit Fly Symposium Fig. 2. Abundance of Ceratitis capitata in infested areas of Croatia. uninfested areas. Research on its bioecology and MATERIALS AND METHODS control (bait spraying) has also been carried out. Rhagoletis cerasi is present in all areas where Surveys for Medfly sweet cherry and sour cherry are grown, infesting Traps of the Chromotrap type (Isagro, Italy) were them on a regular basis. Owing to severe crop used in all detection and monitoring activities. losses during the last few decades, tree numbers Traps were baited with trimedlure, ammonium have greatly declined. However, sweet cherry salts (diammonium hydrogen phosphate; Pliva cultivation has increased recently with the intro- d.d.) and ammonium sulphate (Isagro, Italy). The duction of new rootstocks, including a self-fertiliz- Chromotrap traps were set up in early June 2001 ing variety. For this reason, this pest is likely to in plantations of fig, apricot, peach, mandarin, increase in economic importance . persimmon and kiwi fruit. Five traps per hectare From June to November 2001 we conducted were set in all cases. Traps were serviced weekly surveys to determine the current distribution and and lures were replaced every four weeks. From abundance of B. oleae and C. capitata. Fruit hosts June to December 2001, fruits were collected were also sampled to determine fruit infestation from the beginning of ripening for each crop levels. From these data, area-specific manage- until the end of the picking period to determine ment strategies were developed. larval infestation. Samples were usually collected Bjelis4 & Pelicaric:' Tephritid fruit fly pests in Croatia: an overview 327 Fig. 3. Bactrocera oleae monitoring sites in Croatia, each site indicated by a black dot. every two weeks. Fruits were counted, weighed, pelago) and central (Brac,4 Hvar, Vis and Solta4 and placed in fruit-holding boxes collect any islands) Dalmacija. Figure 1 shows that the emerging flies. The sand in the holding boxes was distribution of Medfly has increased since sieved weekly for pupae. Pupae were held until the last survey in 1980. Medfly was detected for emergenceandthenumberandspeciesrecorded. the first time in the Neretva River valley, where the pest has been absent to date, and was pres- Surveys for olive fly ent at 19 of the 60 trap sites in the Neretva valley. Chromotrap traps (Isagro, Italy) baited with the The trapping data indicate differences in adult female sex pheromone (1,7, dioxaspiro (5,5) numbers and seasonal occurrence in the differ- undecan), ammonium salts (diammonium hydro- ent survey areas (Fig. 2). This is most likely due to gen phosphate and ammonium sulphate), and differences in host availability and abundance hydrolysed protein, were used to monitor for and climatic conditions. B. oleae. Traps were checked weekly and lures The Dubrovnik and Stone areas are the southern- were replaced as specified by the manufacturer. most sections of the Dalmatia region (Fig. 2). Observations of larval stages in olive fruits were Both areas have a mild climate. Temperatures made by collecting fruit every two weeks. Fruits rarely fall below 0°C in the winter and early were stripped and number of larval stages were spring. A large number of cultivated plant species recorded and placed on sand in holding boxes to (including loquat, apricot, fig, peach, persimmon, collect any emerging flies. tomato, mandarin, orange, bitter orange, pome- granate) probably resulted in the occurrence of RESULTS adults from early June to late November. A combi- nation of small-scale commercial orchards and Medfly uncontrolled populations of Medfly in backyards The current distribution of Medfly in Dalmatia is with numerous hosts makes it possible for the presented in Fig. 1. Trapping confirmed the pest to have four to five generations per year. presence of this species in all areas surveyed, with The Neretva valley is geographically isolated, the exception of the county of Zadar. Although with a small number of hosts (Fig. 2). Mandarin is the area was not sampled, we consider it likely the species most intensively cultivated, with that Medfly is also present in the insular area a small number of fig and peach orchards. The in southern (Korcula4 & Mljet islands; Elaphyt archi- Neretva valley is subject to cold winters (frosts in 328 Proceedings of the 6th International Fruit Fly Symposium Fig. 4. Abundance and level of infestation of olive fruits by Bactrocera oleae pre-imaginal stages in some olive- growing areas. December and January) and hot summers (approx- fig and peach and mandarin orchards). imately 35°C). Medfly occurred in the area in Sep- The Split area, from Omis4 to Kastela4 (Fig. 2), has a tember, after the temperature had dropped, and number of Medfly hosts with various ripen- after the late summer period. Medfly infestation ing times. The climate is mild and it is also a tour- in the Neretva valley was low (<2%), and oc- ist area, with a number of backyard gardens, indi- curred only in mixed orchards (individual trees in vidual trees, gardens and small fig, peach, sweet Bjelis4 & Pelicaric:' Tephritid fruit fly pests in Croatia: an overview 329 cherry and mandarine orchards. The first Medfly of SIT should be considered for suppression of adults were caught in August. Fruit damage in Medfly in these areas. the area was significant since neither individual nor coordinated control of Medfly was imple- Olive fly mented. An olive fly monitoring programme and the Sibenik4 is not a significant fruit-production development of new control methods represents area. Olive is the most commonly cultivated crop. the basis for an overall management strategy for Tourist facilities along the coast, numerous host olive fly. Owing to an increase in the planting of plants in backyards and the absence of control new olive groves that has been encouraged by the measures make it possible for Medfly to spread in Ministry of Agriculture and Forestry, there has this area, which had not previously been infested. been an increase in the importance of olive fly. Since Croatia is competing on an international Olive fly market which is based on organic olive produc- Distribution, adult abundance and fruit infesta- tion, control of olive fly must be compatible with tion of olive fly are shown in Figs3&4.Olive organic or environmentally-compatible produc- fly was present in all areas surveyed. Assess- tion. It is expected that the mass-trapping method, ments of olive fruit infestation (third larval instars, which is easy to implement, will fully replace con- pupae, exit holes) showed that yield losses caused ventional control methods for this pest. by this pest were significant, with infestations of More than a half of all olive-growing areas in over 80% being recorded in October 2001 in Croatia are located on the islands, which have Brsecine4 and Ravnice (Fig. 4). Olive infestation remained well-preserved and unpolluted. On levels were much lower on islands off the coast some of the islands (e.g. Hvar, Dugi Otok), olive fly (data not presented). Trapping and fruit sampling infestations are frequently low, so that insecticide data indicate that the most intensive infestation usage is minimal. Spatial isolation of these areas was caused by the second and third generations. is an advantage in the possible application of SIT Populations appeared to increase in the second as a control method over large areas.