Tephritid fruit fly pests in Croatia: an overview of damage and currentcontrol strategies

M. Bjelis* & V. PelicaricInstitute 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 ofMediterranean fruit fly (Medfly), Ceratitis capitata, and olive fly, Bactrocera oleae, from June toNovember 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 forboth species based on the survey results are discussed.

INTRODUCTIONThree economically significant tephritid fruit fly

species occur in the littoral and insular regions ofCroatia: the olive fly, Bactrocera oleae Gmelin, theMediterranean fruit fly, Ceratitis capitata (Wiede-mann), and the cherry fruit fly, Rhagoletis cerasiLoew. The most numerous and commonly culti-vated fruit species are hosts and include olive, Oleaeuropea; grape, Vitis vinifera; mandarin, Citrusreticulata; fig, Ficus carica, peach, Prunus persica;sweet cherry, Prunus avium; sour cherry, Prunuscerasus, and apricot, Prunus armeniaca. Less com-mon hosts include loquat, Eriobotrya japonica;persimmon, Diospyros kaki; pear, Pyrus comunis;and apple, Malus domestica.

Bactrocera oleae is the most significant olive

fruit pest. This pest is managed by cover sprayingthe entire tree with organophosphate insecticides,by bait spraying with a mixture of protein andorganophosphate insecticide, or is not managedat all. Research has been carried out during thelast few decades on new control methods such asmass-trapping, and testing of natural insecticides,repellants and ready-made baits (Brnetic1989;Pelicaric & Bjelis 2002; Bjelis & Pelicaric 2002b).

Ceratitis capitata has been present in theCroatian littoral regions for over 50 years (Kova-cevic 1960) (Fig. 1). It is becoming an increas-ingly important pest in the region of Dalmatia(Bjelis & Pelicaric 2002a), particularly in citrusproduction. This pest was not managed in thepast. Education of fruit growers on plant quaran-tine measures has been carried out to minimizecrop losses and reduce Medfly expansion into

*To whom correspondence should be addressed.E-mail: mario.bjelis@zzb.hr

Fig. 1. Historical distribution of Ceratitis capitata in Croatia.

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Proceedings of 6th International Fruit Fly Symposium6–10 May 2002, Stellenbosch, South Africa

pp. 325–329

uninfested areas. Research on its bioecology andcontrol (bait spraying) has also been carried out.

Rhagoletis cerasi is present in all areas wheresweet cherry and sour cherry are grown, infestingthem on a regular basis. Owing to severe croplosses during the last few decades, tree numbershave greatly declined. However, sweet cherrycultivation has increased recently with the intro-duction of new rootstocks, including a self-fertiliz-ing variety. For this reason, this pest is likely toincrease in economic importance .

From June to November 2001 we conductedsurveys to determine the current distribution andabundance of B. oleae and C. capitata. Fruit hostswere also sampled to determine fruit infestationlevels. From these data, area-specific manage-ment strategies were developed.

MATERIALS AND METHODS

Surveys for MedflyTraps of the Chromotrap type (Isagro, Italy) were

used in all detection and monitoring activities.Traps were baited with trimedlure, ammoniumsalts (diammonium hydrogen phosphate; Plivad.d.) and ammonium sulphate (Isagro, Italy). TheChromotrap traps were set up in early June 2001in plantations of fig, apricot, peach, mandarin,persimmon and kiwi fruit. Five traps per hectarewere set in all cases. Traps were serviced weeklyand lures were replaced every four weeks. FromJune to December 2001, fruits were collectedfrom the beginning of ripening for each cropuntil the end of the picking period to determinelarval infestation. Samples were usually collected

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Fig. 2. Abundance of Ceratitis capitata in infested areas of Croatia.

every two weeks. Fruits were counted, weighed,and placed in fruit-holding boxes collect anyemerging flies. The sand in the holding boxes wassieved weekly for pupae. Pupae were held untilemergence and the number and species recorded.

Surveys for olive flyChromotrap traps (Isagro, Italy) baited with the

female sex pheromone (1,7, dioxaspiro (5,5)undecan), ammonium salts (diammonium hydro-gen phosphate and ammonium sulphate), andhydrolysed protein, were used to monitor forB. oleae. Traps were checked weekly and lureswere replaced as specified by the manufacturer.Observations of larval stages in olive fruits weremade by collecting fruit every two weeks. Fruitswere stripped and number of larval stages wererecorded and placed on sand in holding boxes tocollect any emerging flies.

RESULTS

MedflyThe current distribution of Medfly in Dalmatia is

presented in Fig. 1. Trapping confirmed thepresence of this species in all areas surveyed, withthe exception of the county of Zadar. Althoughthe area was not sampled, we consider it likelythat Medfly is also present in the insular areain southern (Korcula & Mljet islands; Elaphyt archi-

pelago) and central (Brac, Hvar, Vis and Soltaislands) Dalmacija. Figure 1 shows that thedistribution of Medfly has increased sincethe last survey in 1980. Medfly was detected forthe first time in the Neretva River valley, wherethe pest has been absent to date, and was pres-ent at 19 of the 60 trap sites in the Neretva valley.

The trapping data indicate differences in adultnumbers and seasonal occurrence in the differ-ent survey areas (Fig. 2). This is most likely due todifferences in host availability and abundanceand climatic conditions.

The Dubrovnik and Stone areas are the southern-most sections of the Dalmatia region (Fig. 2).Both areas have a mild climate. Temperaturesrarely fall below 0°C in the winter and earlyspring. A large number of cultivated plant species(including loquat, apricot, fig, peach, persimmon,tomato, mandarin, orange, bitter orange, pome-granate) probably resulted in the occurrence ofadults from early June to late November. A combi-nation of small-scale commercial orchards anduncontrolled populations of Medfly in backyardswith numerous hosts makes it possible for thepest to have four to five generations per year.

The Neretva valley is geographically isolated,with a small number of hosts (Fig. 2). Mandarin isthe species most intensively cultivated, witha small number of fig and peach orchards. TheNeretva valley is subject to cold winters (frosts in

Bjelis & 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.

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December and January) and hot summers (approx-imately 35°C). Medfly occurred in the area in Sep-tember, after the temperature had dropped, andafter the late summer period. Medfly infestationin the Neretva valley was low (<2%), and oc-curred only in mixed orchards (individual trees in

fig and peach and mandarin orchards).The Split area, from Omis to Kastela (Fig. 2), has a

number of Medfly hosts with various ripen-ing times. The climate is mild and it is also a tour-ist area, with a number of backyard gardens, indi-vidual trees, gardens and small fig, peach, sweet

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.

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cherry and mandarine orchards. The first Medflyadults were caught in August. Fruit damage inthe area was significant since neither individualnor coordinated control of Medfly was imple-mented.

Sibenik is not a significant fruit-productionarea. Olive is the most commonly cultivated crop.Tourist facilities along the coast, numerous hostplants in backyards and the absence of controlmeasures make it possible for Medfly to spread inthis area, which had not previously been infested.

Olive flyDistribution, adult abundance and fruit infesta-

tion of olive fly are shown in Figs 3 & 4. Olivefly was present in all areas surveyed. Assess-ments of olive fruit infestation (third larval instars,pupae, exit holes) showed that yield losses causedby this pest were significant, with infestations ofover 80% being recorded in October 2001 inBrsecine and Ravnice (Fig. 4). Olive infestationlevels were much lower on islands off the coast(data not presented). Trapping and fruit samplingdata indicate that the most intensive infestationwas caused by the second and third generations.Populations appeared to increase in the secondhalf of August, after the hot and dry summerperiod. The first olive fly generation can alsocause significant crop losses, but only in smallerproduction areas that are mainly located in thesouth (Brsecine,Omis,Split,Kastela,Marina,Zadar).

DISCUSSION

MedflyThis study showed that Medfly is of increasing

economic importance in Croatia. It is particularlyimportant in areas with intensive horticulturalproduction, of mainly mandarin and stone fruit.At present, Medfly can be controlled with conven-tional control methods such as bait spraying.However, particular attention should be paid toproduction areas where Medfly has recentlyspread or is present at low levels, in particular theNeretva valley (5000 hectares) where Medflycauses very little damage. Since the Neretva valleyis an important mandarin-production area, sup-pression or eradication of Medfly should be consid-ered.

The Neretva valley is ideal for the application ofthe sterile insect technique (SIT) as it is geographi-cally isolated. Small settlements on the coastline,and backyards with numerous fruit fly hosts,narrow the feasible control options. Application

of SIT should be considered for suppression ofMedfly in these areas.

Olive flyAn olive fly monitoring programme and the

development of new control methods representsthe basis for an overall management strategy forolive fly. Owing to an increase in the planting ofnew olive groves that has been encouraged by theMinistry of Agriculture and Forestry, there hasbeen an increase in the importance of olive fly.

Since Croatia is competing on an internationalmarket which is based on organic olive produc-tion, control of olive fly must be compatible withorganic or environmentally-compatible produc-tion. It is expected that the mass-trapping method,which is easy to implement, will fully replace con-ventional control methods for this pest.

More than a half of all olive-growing areas inCroatia are located on the islands, which haveremained well-preserved and unpolluted. Onsome of the islands (e.g. Hvar, Dugi Otok), olive flyinfestations are frequently low, so that insecticideusage is minimal. Spatial isolation of these areasis an advantage in the possible application of SITas a control method over large areas.

ACKNOWLEDGEMENTSThe authors would like to thank the Ministry of

Agriculture and Foresty of the Republic of Croatia,the Counties of Dubrovnik and Neretva, for fund-ing this project, and Sonya Broughton for review-ing the original manuscript.

REFERENCESBJELIS, M. & PELICARIC, V. 2002a. Results of Ceratitis capi-

tata Wied. (Diptera, Tephritidae) detection andmonitoring in Republic of Croatia during year 2001.Croatian Plant Protection Society Meeting. In:Maceljski, Glasilo Biljne Zastite No. 1.

BJELIS, M. & PELICARIC, V. 2002b. Olive fruit fly – Bactro-cera oleae Gmel. (Diptera, Tephritidae) control byusing of copper products. Croatian Plant ProtectionSociety Meeting. In: Maceljski, Glasilo Biljne ZastiteNo. 1

BRNETIC, D. 1968. Contribution to knowledge of dryattractants efficacy on mediterranean fruit fly. Agro-hemija No. 5–6. (In Croatian. )

BRNETIC, D. 1989. Visual and olfactory stimuli regard-ing the olive fly (Dacus oleae Gmel.) on the KornatiArchipelago. International Symposium of OliveGrowing, Cordoba, Spain, 26–27 September 1989.Olea No. 20: 97.

KOVACEVIC, Z. 1960. Mediterranean fruit fly – Cera-titis capitata W. (Diptera, Tephritidae) as new prob-lem. Proceedings of ‘Agronomski Glasnik’ .

PELICARIC, V. & BJELIS, M. 2002. IPM and new strategiesfor olive fruit fly control. In: ‘Nocnjak’ Proceedings,Biograd na moru, 22–23 March 2002. 25–31.

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