Introduction

Dasineura oleae Angelini (1831) has been reported as a native gall inducer on olive, Olea europaea L., in the whole Mediterranean area from the most western part in Portugal up to the eastern part (Syria, Lebanon, Jordan, Israel and the Palestinian Territories). The galls induced by D. oleae affect the distribution of nutrient elements in the infested leaf tissues and other vegetative organs of olive trees, especially in the stalks of flowers (inflorescence). Infestation of the stalks by D. oleae may additionally lead to yield loss. Galls induced in these tissues interrupt the nutrient flow to the growing fruits, and small-sized fruits are produced (Batta 2019).

Al-Tamimi (1997) showed that the olive leaf gall midge is widely distributed in Jordan in all economically olive planted orchards. At some sites, it causes serious damage by infesting up to 55–62% of leaves. Darvas et al. (2000) evaluated D. oleae as a serious pest in Syria and a causer of damages in other countries of the Mediterranean area. D. oleae has been generally accepted as a secondary pest of olive in Turkey and in the countries of Mediterranean region (Skuhravá and Skuhravý 1997). Al-Tamimi (1997), Hrncic (1998), Simoglou et al. (2012) and Boselli and Bariselli (2015) stated that D. oleae has been considered as an important pest of some olive orchards in Jordan, Montenegro, Greece and Italy, respectively. In Turkey, the olive leaf gall midge has been reported from Bursa, Denizli, Antalya, Hatay and the Aegean region (Trotter 1903; Alkan 1952a, b; İyriboz 1968; İren and Ahmet 1973; Skuhravý et al. 1980; Skuhravá et al. 2005). Doğanlar et al. (2011) mentioned that D. oleae and its parasitoids develop high population densities in the Hatay province (Turkey) by their works in the period from 2007 to 2010. In the Palestinian Territories, Batta (2019) reported the presence of D. oleae as a serious pest on olive trees grown at different sites and governorates of the country.

Larvae of D. oleae cause slight, indefinite, elongate swellings (galls) on olive leaves (Fig. 1a–c). Per gall, only one larva develops. The whole development from egg to adult takes place inside the gall. Galls of D. oleae may also occur on terminal parts of young shoots of olive trees if the density of gall midge population in the area is high (Coutin and Katlabi 1986; Avidov and Harpaz 1969; Al-Tamimi 1997; Darvas et al. 2000; Batta 2019). Usually, only one generation per year develops in many areas of olive production in several countries of Mediterranean region (Al-Tamimi 1997; Darvas et al. 2000; Doğanlar et al. 2011), but at favorable conditions a second generation may develop at certain sites as in the subcoastal regions of olive production in the eastern Mediterranean countries such as Syria and the Palestinian Territories (Baidaq et al. 2015; Ramadhane et al. 2017; Batta 2019). The adult flies of D. oleae are usually present in the field from March to the beginning of May for the first generation and from October to the beginning of November for the second generation (Batta 2019).

Fig. 1
figure 1

Damage caused by Dasineura oleae on olive trees and mode of parasitism by indigenous parasitoids, a damage caused by D. oleae on leaves and shoots of olive trees, b infestation with D. oleae on olive leaves appeared as indefinite and elongate galls on the lower leaf surface, c: enlarged view of D. oleae gall on the lower surface, d–e circular exit holes for emergence of the adult parasitoids from D. oleae galls, f emergence of D. oleae adults after completing the life cycle in form of irregular exit hole with puparium left near the hole after emergence, g–h unparasitized pupae of D. oleae, i–k parasitized pupae of D. oleae with different developmental stages of the parasitoid living inside the pupae. Scale bars = 100 μm (in the above illustrations)

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Only little work has been conducted on mortality factors of D. oleae. Doğanlar (1992) mentioned D. oleae on leaves and flowers of O. europaea as new host for Quadrastichus sajoi (Szelenyi) from Syria. Al-Tamimi (1997) stated that climatic conditions such as temperature and relative humidity, in addition to the natural enemies, especially the parasitoids, were given as the main mortality factors of D. oleae in Amman district, Jordan. Doğanlar et al. (2009) reared and described Quadrastichus dasineurae Doğanlar, LaSalle, Sertkaya and O. Doğanlar (Hymenoptera, Eulophidae) as larval parasitoid of D. oleae in Hatay province, Turkey. Doğanlar (2011) reared some parasitoids from galls of D. oleae and Lasioptera oleicola Skuhravá on leaves and shoots of O. europaea as larval and pupal parasitoids of D. oleae in Hatay province, Turkey.

In the Palestinian Territories, olive trees are cultivated in areas with variable altitudes ranging from 82 m above sea level (a.s.l.) in the subcoastal areas to 635 m a.s.l. in the hilly areas. The infestation rates with D. oleae in relation to the altitudes of the areas planted with olive trees have not been studied in this country. Similarly, parasitism on D. oleae has not been examined in this country. Therefore, the objectives of the present study were: (1) to determine the infestation rate with D. oleae on the leaves of olive trees cultivated at variable altitudes, (2) to identify the species of indigenous parasitoids on the larvae of D. oleae, (3) to describe the species of indigenous parasitoids by providing with the necessary illustrations, (4) to determine the overall rates of parasitism on D. oleae by the identified indigenous parasitoids in the sampling sites with variable altitudes, (5) to partition the overall rates of parasitism on D. oleae between the identified species of parasitoids in the sampling sites and check the relationship between the rate of parasitism and the altitude of the sampling sites.

Materials and methods

Collection of samples from different sampling sites of olive production areas

Samples of leaves and branches of infested olive trees with D. oleae were collected from different sampling sites spreading in olive production areas of the Palestinian Territories. Sampling sites have the following altitudes and coordinates: Kadouri in Tulkarm governorate (82 m a.s.l., coordinates: 32°18′48.3″N 35°01′19.9″E); Aljarochia in Tulkarm governorate (102 m a.s.l., coordinates: 32°20′48.0″N 35°02′50.5″E); Wadi Kana in Sulfeet governorate (229 m a.s.l., coordinates: 32°09′28.7″N35°06′38.5″E); Seilet El-Dahr in Jenin governorate (492 m a.s.l., coordinates: 32°18′52.8″N 35°11′21.4″E) and Assira El-Shamalieh in Nablus governorate (635 m a.s.l., coordinates: 32°14′59.9″N 35°16′05.6″E). Four plots with five olive trees each were randomly chosen in each sampling site (1000 m2 area planted with olive trees). Then, randomly chosen samples of leaves and branches were collected from chosen plots within each site during the study that took place from November 15 (2018) to February 15 (2019) (the number of leaves collected per plot is indicated in Tables 1 and 2). The average annual temperature in the sampling sites was 14.8 °C (6–39 °C), and the average annual relative humidity was 58.9% (32–100%) (PMA 2018). The purpose of collecting the samples was to determine the infestation rates with D. oleae on olive trees and to determine the overall rates of parasitism caused by the indigenous parasitoids on D. oleae galls in the sampling sites.

Table 1 Rate of infestation with Dasineura oleae on olive trees and overall rate of parasitism on D. oleae at different sampling sites of olive production areas of the Palestinian Territories during the period from November 15, 2018, to February 15, 2019. Four plots were randomly taken in each sampling site (1000 m2 area planted with olive trees), and each plot contained five neighboring olive trees within the site
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Table 2 Partitioning of the overall rates of parasitism (indicated in Table 1) between two identified species of parasitoids on Dasineura oleae on olive trees at different sampling sites in the Palestinian Territories during the period from November 15, 2018, to February 15, 2019. Four plots were randomly taken in each sampling site (1000 m2 area planted with olive trees), and each plot contained five neighboring olive trees within the site
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Determination of infestation rates of olive trees with D. oleae in the different sampling sites

To determine the infestation rates with D. oleae, randomly chosen samples of olive leaves were collected from chosen plots in the sampling sites of olive production areas (four plots with five olive trees each per sampling site of 1000 m2 area planted with olive trees as indicated in the previous section: collection of samples from different sampling sites). The following method was used to determine the rate of infestation: (1) counting the total number of leaves examined in each plot per sampling site, (2) counting the number of infested leaves with D. oleae in each plot per sampling site. The infested leaves should have the characteristic galls of D. oleae that could be seen on the lower leaf surface (Fig. 1b–c), (3) calculating the percentage of infestation with D. oleae on the leaves of each plot in each sampling site, and (4) calculating the average percentage of infestation with D. oleae per sampling site in each governorate. All counts for determining the infestation rate were repeated twice at different times during the period of the study for confirmation.

Rearing of indigenous parasitoids from D. oleae galls in the collected samples

For promoting the emergence of adult parasitoids from galls of D. oleae, the collected samples of infested leaves were incubated in closed transparent plastic bags (dimensions: 35 × 25 cm). Incubation of samples was done in an incubator under the following conditions: temperature of 20 ± 2 °C and illumination of 16 h per day. For each plot in each sampling site, emerged adult parasitoids were collected using an aspirator then preserved in screw-caped vials with 70% ethanol as a mounting medium for being identified and then described. The incubation period was extended until the emergence of all adult parasitoids from infested galls in the samples (collection time was elapsed from November 15, 2018, to February 15, 2019).

Description and identification of indigenous parasitoids reared from D. oleae galls

Specimens of males and females of the parasitoids preserved in screw-caped vials with 70% ethanol as a mounting medium were used for identification and description of the parasitoid species reared from D. oleae galls on the infested leaves. Adults of each parasitoid species were morphologically examined under the dissecting and compound microscopes. Afterward, preparations of microscopic slides for the different body parts of these adults were made to be examined during the identification. Representative pictures for the male and female adults of parasitoids and their body parts were taken. Finally, microscopic examination for identifying and describing of each parasitoid species was performed. Illustrations were also provided for the following characteristics: body color, female and male genitalia, the mesosoma, the gaster, the antennae and legs, in addition to the venation of the fore wings. These characteristics were used in the description of each parasitoid species.

Determination of overall rates of parasitism on D. oleae galls in the different sampling sites

The randomly chosen samples of infested leaves with D. oleae were taken from the different plots (four plots with five olive trees each per sampling site of 1000 m2 area planted with olive trees as indicated in the previous section: collection of samples from different sampling sites). These samples were used to determine the overall rate of parasitism on D. oleae galls in the different sampling sites. The period of this study has extended from November 15, 2018, to February 15, 2019. The following method was used during the study: (1) counting the total number of D. oleae galls on the infested leaves in each plot and in each sampling site then, (2) counting the total number of parasitized galls of D. oleae on the sampled leaves in each plot and in each sampling site. The parasitized galls are characterized by having circular exit holes in their walls (Fig. 1d-e) that clearly indicate the emergence of the adult parasitoids, whereas the unparasitized galls of D. oleae have irregular holes (ruptures) in their walls. In addition, the pupal skins (puparia) are left behind when the adult flies emerge from pupae (Fig. 1f), (3) calculating the percentage of overall rate of parasitism on D. oleae galls on the infested leaves of each plot and each sampling site, and (4) calculating the average percentage of overall rate of parasitism per sampling site in each governorate for the different species of indigenous parasitoids on D. oleae galls. All counts to determine the overall rates of parasitism were repeated twice at different times during the period of the study for confirmation.

Partitioning of the overall rates of parasitism between the identified species of indigenous parasitoids of D. oleae in the different sampling sites

After identification of each parasitoid species reared from galls of D. oleae in the different sampling sites of olive production areas, samples of preserved specimens of parasitoid adults in screw-caped vials with 70% ethanol were used during the study. The preserved specimens represent the parasitoids in the sampling sites (four plots with five olive trees each per sampling site of 1000 m2 area planted with olive trees as indicated in the previous section: collection of samples from different sampling sites). The percentage of each parasitoid species in each plot and in each sampling site was determined according to the following method: (1) taking four samples of preserved specimens of parasitoid species representing four plots chosen per sampling site. Each sample contains the two species of parasitoids reared from D. oleae galls specific to the plots of sampling site, (2) counting the total number of preserved specimens of the two species of parasitoid adults in the plot, (3) counting the number of each species of parasitoid specimens in the plot according to the identified morphological characters of each species, (4) calculating the percentage of each parasitoid species in the sample in relation to the total number, (5) calculating the average percentage of each parasitoid species in the plots per sampling site and governorate. Collecting and preserving of parasitoid specimens elapsed from November 15, 2018, to February 15, 2019. All counts for determining the rate of parasitism by each parasitoid were repeated twice at different times during the period of the study for confirmation.

Data analyses

Statistical analysis was performed on the data obtained on the average % of infestation rates with D. oleae per plot in the sampling sites and governorate, and the average % of overall rate of parasitism by the two species of parasitoids on D. oleae galls per sampling site and governorate, in addition to the average % of each parasitoid species per plot in the sampling site and governorate. The analysis performed includes calculating of the standard error of the means (SE) in the different plots of the sampling sites and adding it to the means “Mean ± SE” as shown in Tables 1 and 2. Analysis of variance (ANOVA) and means’ separation by Tukey HSD were conducted to check the presence of significant differences between the means in the different plots of sampling sites. Significance level was set at P < 0.05. All analyses were performed with the statistical software SAS® (SAS Institute, Cary, NC, USA).

Results

Rate of infestation of olive tree leaves with D. oleae versus altitude of sampling sites

The average % of infestation with D. oleae on the sampled leaves of olive trees in the different sampling sites representing the governorates of the Palestinian Territories varied from 12.1% in Assira El-Shamalieh (635 m a.s.l.) to 52.7% in Wadi Kana (229 m a.s.l.) (Table 1). At higher altitude such as Seilet El-Dahr (492 m a.s.l.) and Assira El-Shamalieh (635 m a.s.l.), the average % of infestation rate was lower, 23.7% and 12.1%, whereas at lower altitudes such as Kadouri (82 m a.s.l.), Aljarochia (102 m a.s.l.) and Wadi Kana (229 m a.s.l.), the average % of infestation rate was higher, 50.5%, 43.1% and 52.7% (Table 1). Significant differences (at P ≤ 0.05) were obtained between the values of average % of infestation with D. oleae in the different sampling sites distributed over a range of altitudes from 82 to 635 m a.s.l. The overall average % of infestation with D. oleae in the different sampling sites of the Palestinian Territories was 36.4% (Table 1). These results indicate that the rate of infestation with D. oleae depends upon the altitude of the area in which olive trees are cultivated.

Description and identification of the parasitoids reared from D. oleae galls

Two species of indigenous hymenopterous parasitoids were reared from galls of D. oleae and then identified as Platygaster oleae Szelenyi (Platygastridae) and Zeytinus hatayensis Doganlar (Eulophidae) (new record for the Palestinian Territories). For this identification, morphological characters of males and females of each parasitoid species were described and then compared with the characters of the species described by the key given by Doğanlar (2011). The necessary illustrations for describing the above-mentioned characters are provided in Fig. 2.

Fig. 2
figure 2

Specific morphological characteristics of indigenous parasitoids of Dasineura oleae that distinguish them from other parasitoid species, a–b lateral views of female and male adults of Platygaster oleae, respectively, c dorsal view of the characteristic mesonotum and scutellum of P. oleae, d–e lateral views of ovipositor and aedeagus of female and male of P. oleae, f characteristic fore wing base of P. oleae adult, g: characteristic antenna of P. oleae adult, h: characteristic hind leg of P. oleae adult, i–j lateral views of female and male adults of Zeytinus hatayensis, respectively, k dorsal view of the characteristic mesonotum and scutellum of Z. hatayensis, l characteristic fore wing base of Z. hatayensis, m: ventral view of the gaster showing the ovipositor of Z. hatayensis female, n: lateral view of the gaster showing the aedeagus of Z. hatayensis male, o–p characteristic antennae of female and male of Z. hatayensis, respectively, q characteristic hind leg of Z. hatayensis adult. Scale bars = 100 μm (in the above illustrations)

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Platygaster oleae Szelenyi

is an endoparasitoid in the larvae of D. oleae and develops inside it until the emergence of adult parasitoid. Morphological characters of the male and female adults that distinguish them from other parasitoid species are given in Fig. 2. The mean body length for the females = 1.12 ± 0.13 mm (n = 50 specimens) and for males = 0.90 ± 0.15 mm (n = 50 specimens).

Zeytinus hatayensis Doğanlar

is an endoparasitoid in the larvae of D. oleae and develops inside it until the emergence of adult parasitoid. Morphological characters of the male and female adults that distinguish them from other parasitoid species are given in Fig. 2. The mean body length for the females = 1.33 ± 0.15 mm (n = 50 specimens) and for males = 1.03 ± 0.17 mm (n = 50 specimens).

Evaluation of parasitism by the indigenous parasitoids on D. oleae

Females of the parasitoids of P. oleae and Z. hatayensis own a long, appendicular ovipositor for thrusting the walls of D. oleae galls and then depositing eggs inside the galls near the host larvae that live inside the galls. The hatched larvae of the parasitoid penetrate the larvae of D. oleae and feed inside it possibly causing its death (Fig. 1i–k). Parasitized larvae of D. oleae are characterized by having partially or completely dark color (Fig. 1i–k) compared to the unparasitized larvae with yellow color (Fig. 1g–h). When the development of parasitoid larvae is completed, they pupate in the gall. Then, the adults emerge from hosting galls by chewing small circular exit holes in the wall of these galls (Fig. 1d–e). If the galls of D. oleae are not parasitized by either P. oleae or Z. hatayensis, the adult flies of D. oleae emerge from hosting gall. This is done by making, first, a rupture in the wall of these galls (irregular exit hole made by the mature pupae; Fig. 1f), and then, second, the adult flies emerge from exited mature pupae by leaving empty pupal skins (puparia) attaching to the leaves near the exit hole (Fig. 1f). This proves that P. oleae and Z. hatayensis are endoparasitoids of larvae and pupae of D. oleae on olive trees grown in the Palestinian Territories, and both species of parasitoids can be reared from galls of D. oleae on infested olive leaves.

Overall rate of parasitism by indigenous parasitoids reared from D. oleae on olive trees in the different sampling sites

The overall rate of parasitism caused by the different species of indigenous parasitoids on D. oleae galls was determined by calculating the average % of the overall rate of parasitism in randomly chosen samples of infested olive leaves with D. oleae in the different sampling sites of the Palestinian Territories (Table 1). The average % of the overall rate of parasitism varied from 12.6% in Assira El-Shamalieh (635 m a.s.l.) to 55.5% in Aljarochia (102 m a.s.l.) (Table 1). At higher altitudes such as Seilet El-Dahr (492 m a.s.l.) and Assira El-Shamalieh (635 m a.s.l.), the average % of overall rate parasitism was lower, 25.6% and 12.6%, respectively (Table 1). However, at lower altitudes such as Kadouri (82 m a.s.l.), Aljarochia (102 m a.s.l.) and Wadi Kana (229 m a.s.l.), the average % of overall rate parasitism was higher, 52.3%, 55.5% and 33.6%, respectively (Table 1). Significant differences (at P ≤ 0.05) were obtained between the values of average % of overall rate parasitism in the different sampling sites. Therefore, the overall rate of parasitism is dependent on the altitude of the area in which olive trees are cultivated. The average % of overall rate of parasitism in the different sampling sites of the Palestinian Territories was 35.9% (Table 1).

Partitioning of the overall rate of parasitism between the identified species of indigenous parasitoids of D. oleae in the different sampling sites

After the identification and description of two parasitoid species from D. oleae (P. oleae and Z. hatayensis), the overall rate of parasitism determined in the above section was partitioned between these species of parasitoids as follows: For P. oleae, it varied from 61.6% in Aljarochia (102 m a.s.l.) to 100% in Seilet El-Dahr (492 m a.s.l.) and in Assira El-Shamalieh (635 m a.s.l.) (Table 2). For Z. hatayensis, it varied from 0% in Seilet El-Dahr (492 m a.s.l.) and in Assira El-Shamalieh (635 m a.s.l.) to 38.4% in Aljarochia (102 m a.s.l.) (Table 2). This would indicate that the average rate of partitioning the overall rate of parasitism depends upon the altitude of the area in which olive trees are cultivated. Significant differences (at P ≤ 0.05) were obtained between the values of average % of partitioning the overall rate of parasitism in the different sampling sites. Also, P. oleae constituted the largest portion in the samples taken at all altitudes (ranged from 61.6% to 100% at 102 to 635 m a.s.l., respectively), whereas Z. hatayensis constituted the smallest portion in the samples taken at the same altitudes (ranged from 0 to 38.4% at 102 to 635 m a.s.l., respectively). Furthermore, P. oleae existed at all altitudes of sampling sites (82 to 635 m a.s.l.), whereas Z. hatayensis existed only at lower altitudes but not at higher ones exceeding 492 m a.s.l. The overall average rate of partitioning of parasitism on D. oleae by the two species of parasitoids in the different sampling sites was 82.7% for P. oleae and 17.3% for Z. hatayensis (Table 2).

Discussion

To our best knowledge, this is the first study demonstrating the relationship between the rate of infestation with D. oleae on olive trees and the altitude of the area cultivated with this crop. However, certain authors reported the infestation rate with D. oleae but without specifying the altitudes of the infested areas. For example, Doganlar et al. (2011) and Perdikis et al. (2015) reported infestation rates of 8.0–78.2% and up to 89% on olive trees grown in Hatay province (Turkey) and in Crete (Greece) without specifying the altitudes of the sampling sites.

In the present study, we were able to prove that the infestation rates with D. oleae are dependent on the altitude of the sampling sites since we found that the infestation rates were more severe in the lower altitudes (82 to 229 m a.s.l.) compared to the higher altitudes (492 to 635 m a.s.l.). A possible explanation for this relationship could be that the lower altitudes are not far from the coast of Mediterranean sea, where temperatures and relative humidity are more favorable for the development of D. oleae compared to the higher altitudes where lower temperatures and less relative humidity are prevailing. Moreover, at the Palestinian conditions, D. oleae produces two generations per year in the subcoastal areas of olive production (lower altitudes) compared to only one generation per year in the hilly areas (higher altitudes) (Batta, 2019).

During the present study, we were able to identify two species of indigenous parasitoids on larvae and pupae of D. oleae on olive trees in the Palestinian Territories: Platygaster oleae and Zeytinus hatayensis. They are considered as the main indigenous parasitoids on D. oleae in the sampling sites because P. oleae possessed the greatest overall average rate of parasitism reaching at 82.7% and spread in all Palestinian sampling sites and governorates, whereas Z. hatayensis possessed the smallest overall average rate of parasitism reaching at 17.3% and spread in few Palestinian sampling sites and governorates. These characteristics would qualify P. oleae to be an excellent candidate for biocontrol of D. oleae on olive trees in the Palestinian Territories. In other countries such as Croatia, Jordan, Greece and Turkey, P. oleae has been reported to be a potential parasitoid on D. oleae and plays an important role in biocontrol of D. oleae (Szelenyi 1940; Al-Tamimi 1997; Fauna europaea 2010; Doganlar 2011).

The overall rate of parasitism on D. oleae is inversely proportional to the altitude of the area planted with olive trees; it was higher at the lower altitudes (82 to 229 m a.s.l.) when compared with the higher altitudes (492 to 635 m a.s.l.). Also, the development of the parasitoids at the lower altitudes was faster in comparison with the higher altitudes (Batta 2019). This could be attributed to the availability of favorable conditions, especially temperature and relative humidity in the areas with lower altitudes compared to the higher altitudes. Doganlar et al. (2011) reported that certain parasitoids of D. oleae such as Z. hatayensis do not exist and develop at higher altitudes in Hatay province (Turkey) because it needs certain levels of temperature and relative humidity for their development. However, high temperature accompanied with low relative humidity (> 35 °C and < 50% r.h.) causes high mortality in the emerged adults of P. oleae at the higher altitudes of olive orchards of Amman district (Jordan) (Al-Tamimi 1997). This would restrict the use of this parasitoid as biocontrol agents of D. oleae at the higher altitudes.

For partitioning of the overall rate of parasitism on D. oleae between the identified species of parasitoids, we were able to allocate certain level of parasitism rate for each one of these parasitoids within the overall rate of parasitism. This allocation is acceptable for assessing the efficacy of each parasitoid species in suppressing D. oleae population when used separately. However, the available literature for assessing the efficacy of each parasitoid species within the parasitoid complex on D. oleae infestation is extremely rare. This could be attributed to the practical difficulty in defining the characteristics of the hole from which each parasitoid species can make to exit from hosting gall. This is because each parasitoid species has its own characteristic exit hole. Doganlar et al. (2011) assessed the overall efficacy of 16 species of parasitoids from five families on D. oleae infestation in Hatay province, Turkey. They reported an overall rate of parasitism reaching at 65% but, they did not allocate certain level of parasitism rate for each one of these parasitoids within the overall rate of parasitism.

In conclusion, in the present study, we were able to determine the rates of infestation with D. oleae on olive trees in the Palestinian Territories and relate these rates to the different altitudes of the sampling sites. We were also able to identify two species of indigenous parasitoids on D. oleae: Platygaster oleae and Zeytinus hatayensis in the studied sampling sites. Other species of indigenous parasitoids may be identified when the sampling process is extended to other sampling sites or in other periods of sampling during the year. The diagnostic characters of these species, in addition to the necessary illustrations, were provided in this study. Furthermore, we determined the overall rates of parasitism on D. oleae by the identified species of parasitoids in the sampling sites, in addition to partitioning of these rates between the identified species of the parasitoids according to the sampling sites. As a result of this partitioning, P. oleae was found to be the dominant species of parasitoids with the largest portion of the overall rates of parasitism, whereas Z. hatayensis possessed the smallest portion of these rates. Moreover, the overall rates of parasitism and its partitioning between the parasitoid species were found to be related to the different altitudes in the sampling sites giving that P. oleae existed in all ranges of altitudes (82 to 635 m a.s.l.), whereas Z. hatayensis existed at low altitudes (82 to 229 m a.s.l.) but not at the altitudes of > 492 m a.s.l. The overall results of this study indicate the significant role of native parasitoids in regulation of D. oleae outbreaks and in the potential use of these parasitoids as biocontrol agents of this insect in the Palestinian Territories.