3.1. Development timeThe development time of O.pityocampae did not significantly differ by gender (t=-1.
78; df=54; p=0.8),and mean egg-to-adult (total)development time of O. pityocampae was11.68±0.07 and 11.
84±0.06days for male and female parasitoids,respectively. Mean egg, larval, and pupal development time of O.
pityocampaewere 1.94±0.01, 3.42±0.03, and 7.
11±0.03, respectively. 3.2.
Longevity of O.pityocampaeThe effect of food on longevity offemale O. pityocampae (F=56.32, df=3, p < 0.001) and maleO. pityocampae (F=276.
46, df=3, p <0.001) was meaningful in termsof the longevity of wasps fed with honey and water diet, and only honey dietwas significantly higher than control for both males and females (p <0.001). There was no significant difference in the female waspslongevity fed with honey and water and just honey (T=0.
94, df=56, p >0.05 Table 1). When exposed to the honey and B. signatum egg, the meanlongevity of O. pityocampae females was estimated to be 19.81 days(Table 1). The longevity of both male and female O.
pityocampae wassignificantly affected by the feeding regime (F=4.41, df=1, p <0.053,Table 1). The longevity of water-fed wasps was significantly lower than that ofthe wasps fed with honey for both males and females (F=91.56, df=3, p <0.001,Table 1). The longevity of female O. pityocampae whose feeding regimewas based on host dependent resources such as host feeding was significantlyhigher than that of female wasps fed with water and significantly lower thanthat of wasps fed with honey (F=90.
87, df=2, p <0.001, Table 1). The adult parasitoids disappearedshortly after emerging in the non-food environment, which shows the importantrole of nutrition in increasing adult parasitoids longevity. Other than this diet, there is no difference between genders of O. pityocampae (T=-1.
60,df=40, p > 0.05, Table 1). 3.
3. Parasitism percentage of O. pityocampaeParasitism is very low in thefirst 24 hours of parasitoid life span and parasitizing B. signatum eggs (7.
27±2.54 eggs) at low levels. Understanding the efficient age of parasitoids is veryimportant to obtain effective and successful parasitism in field releaseprograms as well as for mass production. The maximum number of eggs deposited byone O. pityocampae female wasobserved on the 3rd (39.
27±0.01eggs) days of its adult life span. The egg laying periodof O. pityocampae lasted 14.45±0.68 days (Fig.
1). A female O. pityocampae lays 122.45±4.30 eggs in its whole life time.
The averageadult longevity was 9.09±0.74 and19.81±0.62 days for females and males, respectively. 3.
4. Sex ratio of O.pityocampaeSex ratio of O. pityocampae on B. signatum eggs in the laboratoryis shown in Fig. 2. The sex ratio (female: male) of O.
pityocampae is 4.2:1. 4. Discussion4.1. Development timeAccording to many researchers,there are different types of development timesin Ooencyrtus species at different temperatures and in different hosts.For example, Rahim et al. (20) studied the effect of temperature on the development time of O.
papilionis.Ashmead showed that in this parasitoid no development ofimmatures occurs if the temperature is over 32.5°C. According to the survey byMuesebeck and Dohanian (18) in both O.
kuvanae and O. anasae development from egg to adult takesabout 18-35 days, depending on temperature. Viggiani (27), duringinvestigations on O. gonoceri Viggiani which is the parasitoid of Gonocerusacuteangulatus Goeze, showed thta the preimmaginal development takes place in 8-12 days at 23-26°Cand at 50-70% of R.H. Maple (10) has also reviewed the biology of O.
johnsoniHoward on Murgantia histrionica Hahn eggs. Based on his results, the development of immatures is approximately 17days. Masutti (11) reported that in O. pityocampae on Thaumetopoeapityocampa Denis & Schiffermuller eggs the development from egg to adult takesabout 22-25 days. These apparent contrasting results could be due to usingdifferent hosts.
Our results showed that short developmentperiod of O. pityocampae on B. signatum eggs can be an importantfeature for mass rearing in the biological control of the pest. 4.2.
Longevity of O.pityocampaeThe longevity of wasps fed withhoney and water and just honey was significantly higher than water-fed waspsfor both males and females (p < 0.001), which shows that honey, dueto having having sugars such as Sucrose, Glucose, Fructose, and vitamins, playsa role in increasing longevity toward water (15). The longevity ofOoencyrtus was influenced by temperature and feeding regime. Rahim etal. (20) reported that in O. manii longevity of both sexes decreaseswith an increase in temperature; males live 4 to 1.
2 days at temperatures of15-36°C whilst females live from 10-1.7 days at the same temperatures. The lowerlongevity we observed in female wasps exposed to the honey and B. signatumegg in comparison with that observed for those fed with honey (Table 1) couldbe due to a less favorable feeding regime and/or the occurrence of ovipositionactivity. These results emphasize the importance of providing food sources tothe adult wasps through habitat management (e.
g. flowering plants) to enhanceconservation or augmentation of biological control. 4.3. Parasitism percentage of O.
pityocampaeEgg-laying period, number of eggs, and longevity of eggparasitoids of in vitro depend on many factors, including temperatureand relative humidity. According to many researchers, a change in temperatureand relative humidity can also change longevity, egg-laying period, and numberof eggs laid by wasps (28). In addition, in the different generations of theegg-laying period, number of eggs and longevity is changed. Also, the nature ofthe substrate at the oviposition site may affect rates of parasitism. For instance, in O.
kuvanae, the eggs of the host on red maple(smooth bark) have a higher rate of parasitism than those on oak (rough bark)(3). Aung et al. (1) stated that the reproductivepotential of 4–day–old females of O. nezarae is higher than 20–day–old and 1–day–old females.
Also,Rajapakse et al. (21) stated that the optimum age of Cotesia marginiventrisfor successful parasitism of Spodoptera frugiperda ranged from 48h to 96 h (21) and that C. marginiventris which wereyounger or older than the above age class were not able to parasitize a host.The results of the present study are consistent with the results of thisresearcher. 4.
4. Sex ratio of O.pityocampaeSexratio may be influenced by several factors including temperature, seasonal fluctuations, andmicroorganisms like Wolbachia. For example, in O.
fecundus,all progeny are female if the ovipositing female is subjected to temperaturesof 30°C, but all progeny are male if the ovipositing female is subjected to atemperature of 35°C (9). Battisti et al.(2) reported that males are very rare in natural populations (0.033%), whereas Tiberi et al (23) observed male emergence under laboratory conditions only whentemperature at oviposition exceeded 30°C. Sex ratio of O.
pityocampae parasitoid on the different eggs of host showed that femalesstart egg-laying sequences by laying male eggs early in an oviposition bout inaccordance with the males Ist strategy. These results suggest that changes inthe sex ratio in each batch depend on the number of host eggs. According to thepredictions of the local mate competition model, a decrease in the number ofhosts offered to the females should result in an increased proportion of maleeggs laid (22). When parasitoid wasps lay eggs in a patch,unfertilized eggs may be laid during the early duration of oviposition (5, 8). Such a ‘male-firststrategy’ facilitates the production of optimal sex ratios by femaleparasitoids. If multi foundresses oviposit in a patch, there may be a reductionin clutch size per foundress because of limited oviposition sites in the patch.Higher proportion of male offspring means higher fitness to foundresses, because male offspring have the potential to mate with thefemale offspring of the other foundresses, and the value of males increases (6,7, 30). Therefore, laying more unfertilized eggs at the beginning ofoviposition should also bring a potential benefit to foundresses.
When mating takes place in small patches and involves mostly relatives,theories predict that females are selected to maximize their fitness byproducing few males, just the number necessary to guarantee that all theirdaughters will be inseminated, and a female biased sex ratio will also bringless local mate competition (LMC) among the sibling male offspring (6, 7, 30).But reduction of males also increase the probability of virginity in offspring.Foundresses may reduce the risk by ensuring sufficient male offspring. In addition, in parasitic Hymenoptera, mated females storesperm in the spermatheca and can manipulate offspring sex ratio (males/total offspring) by controlling fertilization duringoviposition. The haplodiploid sex-determination system provides the motherswith a mechanism to control progeny sex ratio, because males develop fromunfertilized eggs (haploid) and females from fertilized eggs (diploid) (5, 29).Tracy and Nechols (25) also reported thatin O.anasae the proportion of females increases with the number of hostsparasitized.
5. ConclusionsAccording to the results of the present study, itseems that this parasitoid can be expressed as a good candidate for massrearing and releasing in nature, because the development time is rather short,and theproportion of high female hasappropriate rate parasitism, and longtime longevity such as singlecharacteristics in terms of considered characteristics have appropriate speciesfor rearing and releasing clump for probability doing besides easy rearing. Theobtained results in this paper reported ease in mass rearing on this parasitoidand effective control of pistachio green stink bug.