Infection status and parasitization rate of Dacineura oleae
During the study, sampling was made in 530 olive groves randomly entered in 160 villages in total (Table 1). From the orchards within the borders of these villages, samples were taken from at least two and maximum 7 orchards only once each year. From the visited olive orchards, 10 shoots were collected and a total of 5310 shoots were examined. A total of 6425 D. oleae gall numbers were found on these shoots. The galls with a parasitoid exit hole were considered as parasitized individuals, and a total of 3016 galls on a district basis and 3459 galls without a parasitoid exit hole were determined (Table 1).
The lowest parasitization rate of olive leaf gall midge in the region was found in Edremit district with 43.6% in 2021, while the highest was found in Havran with 49.8% in 2020. It was revealed that the damage rates and parasitization status were close to each other in all three districts (Table 1).
When the infection rates of D. oleae in olive groves were examined, it was determined that the lowest was in Havran district with 50.2% in 2020, and the highest was in Edremit district in 2020 with 54.8%. Although the infection rates were over 50% in all three districts, they were slightly higher in Edremit district, which were decreasingly followed by Burhaniye and Havran districts (Table 1).
While the population of D. oleae was found to be higher in the orchards close to the sea and also in the sheltered gardens without too much wind flow, it was observed that the population was quite low in the inland orchards as you moved away from the beach, or even almost none in some orchards. The population density in the study was obtained due to samples taken from coastal and low altitude olive orchards in Edremit and Burhaniye districts. Although Havran district does not have a coastline, the results in Table 1 were found due to the population density in the orchards at low altitude and with the sea and humidity effect. As a matter of fact, similar to this study, in the studies conducted in Palestine, it was stated that the rates of D. oleae infection were higher in low altitude orchards compared to the ones in higher altitudes (Batta, 2018; Batta & Doğanlar, 2019).
Table 1
Data of olive orchards sampled between 2019–2021 in Edremit, Havran, and Burhaniye districts (Balıkesir/Turkey) and Dacineura oleae total number of galls (number), number of galls (Number), infected rate (%), parasitoid gall number (pieces) and parasitization rate (%).
District | Year | Number of villages sampled (Number) | Number of orchards sampled (Number) | Number of shoots collected (Number) | Tolat number of galls (Number) | Gall number of D. oleae (Number) | Infection Rate (%) | Number of Parazitoided D. oleae galls (Number) | Parasitization Rate (%) |
Edremit | 2019 | 24 | 85 | 850 | 826 | 450 | 54,5 | 376 | 45,5 |
2020 | 24 | 82 | 820 | 846 | 464 | 54,8 | 382 | 45,2 |
2021 | 25 | 84 | 850 | 874 | 493 | 56,4 | 381 | 43,6 |
| Average | | | | | | 55,3 | | 44,7 |
Havran | 2019 | 13 | 41 | 410 | 347 | 175 | 50,4 | 172 | 49,6 |
2020 | 16 | 48 | 480 | 402 | 202 | 50,2 | 200 | 49,8 |
2021 | 13 | 41 | 410 | 416 | 214 | 51,4 | 202 | 48,6 |
| Average | | | | | | 50,7 | | 49,3 |
Burhaniye | 2019 | 14 | 47 | 470 | 847 | 442 | 52,2 | 343 | 47,8 |
2020 | 16 | 52 | 520 | 823 | 425 | 51,6 | 398 | 48,4 |
2021 | 15 | 50 | 500 | 1044 | 544 | 52,1 | 500 | 47,9 |
Average | | | | | | 52,0 | | 48,0 |
Total | 160 | 530 | 5310 | 6425 | 3459 | | 3016 | |
There are studies on olive leaf warts in the Mediterranean Region countries. In a study conducted in olive groves in the central parts of Italy, it was reported that the average number of D. oleae gall was 23%, but this number was up to 71% in some orchards. In addition, some these were reported to have no parasites at all, while this rate reached at 43.7% in some others (Picchi et al., 2022). In Greece, it was reported that the infestation rate of D. oleae was between 70% and 90% in the study region, but the level of infestation varied between trees and the rate of contamination decreased inland (Simoglou et al., 2012). In Palestine, it was noted that P. oleae and Z. hatayensis were the two local parasitoids of D. oleae, but the parasitization rate of P. oleae reached up to 82.7%, while Z. hatayensis was lower (38.4%) (Batta and Doğanlar, 2019).
Parazitoids of Dacineura oleae
As a result of the study, it was found out that there were 10 species dependent on 4 families belonging to the order Hymenoptera parasiting D. oleae in Edremit, Havran and Burhaniye districts. From 7 species belonging to the Eulophidae family; 3 species belonging to the Zeytinus genus, Z. balikesirensis Doğanlar and Sakin, Z. edremitensis Doğanlar and Sakin, and Z. marmarae Doğanlar and Sakin were identified and named for the first time in this study (Doğanlar et al., 2020). Only one species was obtained from Platygasteridae, Pteromalidae and Torymidae families (Table 2).
Table 2
Parasitoid species of Dacineura oleae identified between 2019–2021 in Edremit, Havran and Burhaniye districts (Balıkesir/Turkey)
Order/Tribe | Family | Species |
Hymenoptera | Eulophidae | Aprostocetus arenarius (Erdös, 1954) |
| | A. flavifrons (Walker, 1849) |
| | A. humilis Graham, 1961 |
| | A. ligus (Walker, 1839) |
| | Zeytinus balikesirensis Doğanlar and Sakin |
| | Z. edremitensis Doğanlar and Sakin |
| | Z. marmarae Doğanlar and Sakin |
| Platygasteridae | Platygaster oleae Szelenyi, 1940 |
| Pteromalidae | Mesopolobus mediterraneus (Mayr, 1903) |
| Torymidae | Torymus phyllireae Ruschka, 1921 |
Studies on the natural enemies of D. oleae (2011) were carried out only in Hatay Province in our country, and in this study, 2 different gall flies, D. oleae and Lasioptera oleicola Skuhravá were determined in olive groves. In the region, 12 species of larvae or pupal parasitoids belonging to 5 families from the order Hymenoptera were detected from both gall flies (Doğanlar, 2011; Doğanlar et al., 2011). Of these species; P. oleae, T. phyllireae and M. mediterraneus were the same as the species found in this study, while the others were different (Table 2). In addition, a new parasitoid species, Quadrastichus dasineurae n. sp. (Hym.: Eulophidae) was identified for the first time (Doğanlar et al, 2009).
From the studies conducted in the Middle East on the parasitoids of D. oleae, the following existences were reported: in the olive groves of the Palestinian Region two native parasitoids of D. oleae, P. oleae and Z. hatayensis (Batta and Doğans, 2019); in the Coastal Region of Syria, Eupelmus urozonus Dalm (Hym.: Eupelmidae) and Z. hatayensis as ecto-parasitoids and Platygaster demades Walker, 1835 (Hym.: Platygasteridae) as endoparasitoids (Ramadhane et al, 2017). In Jordan, along with P. oleae and Aprostocetus sp., 2 other undiagnosed parasitoid species were found to parasitize D. oleae (Al-Tamimi, 1997). In the studies conducted in Italy, on the other hand, P. demades, P. oleae, M. mediterraneus, and M. aspilus (Walker 1835) were identified as parasitizing D. oleae (Tondini and Petacchi, 2019; Picchi et al, 2022).
As a result of the study, 629 parasitoid individuals were examined. Of these species; P. oleae was found to be the most commonly observed species from D. oleae galls with 190 units. This species accounted for 30.2% of the parasitoids from galls. A. ligus with 77 (12.2%) and M. mediterraneus with 75 (11.9%) were the second and third most commonly seen species. The least identified species was T. phyllireae, and only 8 (1.3%) of them were obtained. In addition, the species included in the Zeytinus genus were found slightly less than the Aprostocetus species (Table 3).
Although many parasitoid species were obtained from D. oleae galls in the olive groves of Hatay province; it was reported that among these species, E. urozonus, P. oleae and Q. dasineurae were the most frequently identified species, and they significantly reduce the gall population together with other parasitoids (Doğanlar et al, 2009). In the study conducted in Palestine, it was stated that P. oleae was the most effective parasitoid of D. oleae, it was found in all olive groves and in orchards at every height in the region, and the parasitism rate reached up to 82.7% (Batta and Doğanlar, 2019). Although there were 2 species of parasitoids belonging to the Pteromalidae and Platygasteridae families of D. oleae in Italy, it was reported that only P. oleae was the specific parasitoid of the Gall midge, while the others could parasitize all Cecidomyiidae family species (Picchi et al, 2022).
Table 3
Numbers (Number) and existence rates (%) of parasitoid species of Dacineura oleae identified between 2019–2021 in Edremit, Havran and Burhaniye districts (Balıkesir/Turkey)
Species | Number of Obtained Individuals (Number) | Rate (%) |
Aprostocetus arenarius | 39 | 6.2 |
A. flavifrons | 60 | 9.5 |
A. humilis | 63 | 10.0 |
A. ligus | 77 | 12.2 |
Zeytinus balikesirensis | 39 | 6.2 |
Z. edremitensis | 41 | 6.5 |
Z. marmarae | 37 | 5.9 |
Platygaster oleae | 190 | 30.2 |
Mesopolobus mediterraneus | 75 | 11.9 |
Torymus phyllireae | 8 | 1.3 |
Total | 629 | 100 |