The peach fruit fly B. zonata is one of the most harmful fruit fly species that is found in many regions of the world ⁽¹⁾. It attacked more than 50 types of fruits and vegetables such as guava, mango, peaches, citrus, pumpkin, bitter gourd and apricots ^(2-3). The losses are estimated at approximately 25-100% on peach and apricot fruits, while it reaches 25 - 50% on guava and figs ⁽⁴⁾. Bactrocera zonata has been found in South and Southeast Asia areas, but it has invaded several countries in the Middle East, including Egypt, since 1998. The pest is considered a holometabolous insect that passes through four stages, namely the egg, the larva, the pupa and adults. 

The damage is mainly caused to the fruits from the larval stage because the larvae feed inside the fruits, which leads to its damage and the occurrence of severe damage to the fruits and a decrease in their marketing value ⁽⁵⁾, Another damage occurs during the process of laying eggs on the fruits, which causes obvious deformations on fruit skin, as well as they released some waxy secretions from the egg-laying areas, which leads to early ripening or rotting and its external appearance becomes undesirable .

In Iraq, the first record of the peach fruit fly B. zonata was in 1972 in the fruits that were imported from Bahrain (6).  It was found on peach, watermelon, jet and mango fruits, but it disappeared from Iraq ⁽⁷⁾. In 2016, it reappeared in all citrus and orchards and caused huge economic losses ⁽⁸⁾. Due to poor agricultural quarantine procedures, the distribution of peach fruit flies B. zonata in the orchard’s citrus and other fruits.  In addition, to the import operations of citrus fruits and vegetables from countries where this pest is found (Iran, Saudi Arabia, Egypt and Yemen). It is widespread and dangerous in most citrus and orchards fruits in Iraq, especially in Baghdad, 2016. It has caused a great economic loss on many types of fruits. Due to the speed of its distribution, its adaptation, the wide environmental range suitable for its growth and the number of plant families that are available.

Due to the few local biological studies of this pest as it is a new exotic pet, it needs to know the suitability of plant hosts in the Iraqi environment. The study was designed to determine the effect of a group of plant families and the industrial food media that used to raise Ceratitis capitata on the development period and percentages of immature survival (larval and pupal) of B. zonata.

Three types of citrus fruits were used in this study, mandranin (clementine cultivar), local orange and local bitter orange. The purpose of this experiment is to study the duration of development immature of the peach fruit fly when feeding on these plant hosts. The citrus fruits and the three healthy species were washed with distilled water and placed in cages of the peach fruit fly adults 8 days after their emergence as a natural medium for laying eggs. Eighteen fruits of each type of citrus were used and this quantity was divided into three meals (replicators) in terms of letting insects for a period of exposure of 24 hours. The fruits were collected and each two fruits were placed in a plastic jar with a capacity of 4 liters, which contains a layer of the mixture soil from the bottom and covered with organza fabric and tied with a rubber band from the top. The experiment was carried out in the laboratory at a temperature of 27 ± 2 °C and a relative humidity of 75 ± 5%.

The fruits were monitored daily by observing the change in the color of small spots in yellow and brownish color on the fruit and gradually turning into watery soft areas and then to holes surrounded by a soft area as a result of feeding the larvae. They make a tunnel into the fruit pulp. The monitoring was continued until the last larvae instar.

For the artificial media, the treatment was carried out by transferring newly hatched larvae at a rate of 50 larvae to a sterile plastic jar containing an appropriate amount of the artificial media. The larvae were transferred using a soft brush. The experiment was repeated 4 replications, and the development of larvae was followed up until they reached the pupae stage. The experiments measured the last larval stage (before the pupae stage) from the drop of the larvae into the soil until pupae stage. The period of larvae development was calculated from the date of collecting the fruit to the beginning of its transformation into pupae. The pupae stages were transferred to a plastic jar containing at the bottom a layer of soil and covered with a light layer of it.

Effect of the artificial media on numbers of pupae and adults

The pupae stage was transferred to 1 L jar and they placed them in the bottom.  The jar was covered with a layer of the mixture soil from the bottom and covered with organza fabric and tied with a rubber band from the top. Then the mouth of the jar was covered with a piece of organza that was fixed with a rubber band. The jars were checked daily until the time of adult stage. The experiment was carried out in the laboratory at a temperature of 27 ± 2 °C and a relative humidity of 75 ± 5%.

Statistical analysis

All laboratory experiments were designed according to the Completely Randomized Design (CRD). The data were analyzed using the analysis of variance tables and the means were compared using the least significant difference (LSD) at 0.05 ⁽⁹⁾. The program that used to analyze the data was (GenStat) program.

The results showed that there was a significant difference in the development period of the larval stage of the peach fruit fly B. zonata that was reared on different food media. The use of artificial media led to a reduction in the period of development of the larval stage to 6.67 days, Whereas, the duration ranged from 9.33 to 10.67 days for the treatments of mandarin, bitter orange and local orange, respectively. These treatments were significantly different among them. The results also showed that there were no significant differences in the period of development of the pre-pupa stage. It is a stage present in fully completed insects and occurs after the larva grows to become ready pupa stage. The highest period of development was 2 days when using local orange fruits as a rearing medium, while the minimum development period was 1 day when using local orange fruits.

For the pupae stage, the results showed that the highest period of the pupae stage of peach fruit fly was 12.67 days in the treatment in which the fruits of the clementine cultivar were used. The results differed significantly from the rest of the treatments. It reached 10.67 days, which also differed from the rest of the treatments. There were no significant differences between the treatments of local orange and local orange, which were 9.67 and 9.0 days, respectively. It is also clear that the development period required for adult emergence, represented by the period from egg to adult emergence. It is known as lifetime, recorded the highest life period in the fruit treatment. Mandarin cultivar was reached (23) days, which differed significantly from the other treatments, followed by the treatment of local orange fruits, which amounted to 20.00 days, which differed significantly from the treatments of mandarin fruits and the artificial media, while it did not differ significantly from the treatment of bitter orange fruits. The treatment that artificial media was used gave the shortest life time of 18.67 days, which differed significantly from the other treatments.

Table (1): Effect of the type of Artificial media on the development period of immature peach fruit fly B. zonata in the laboratory at a temperature of 25 ± 2 °C.

* LSD for the treatments = 0.5337

* LSD for the period of development = 0.5337

* LSD for the interaction between the treatments and the period of development = 1.0674

The above results indicate that the type of food media has an effect on the development period of the larval stage of the peach fruit fly. The reason for that was the development of the larvae in the shortest period in the treatment of the artificial media may be attributed to the suitability of that media for rearing the insect, as the content of artificial media was suitable as a good protein and carbohydrate source for feeding the larvae. Which led to the possibility of adopting it for the purposes of quantitative rearing of the insect. 

The results also showed the suitability of these fruits as additives for the growth and development of the immature stages of the insect. The success of these treatments in rearing the insect is probably due to the water content of the fruits, as water is an important source in the first three weeks. It also notes that the treatment of local orange fruits was the longest period of the larval stage than the rest of the fruits. This may be due to the large size of the fruit and its large water content, and this was indicated by ⁽¹⁰⁾ that the larger host had the largest number of eggs. 

⁽¹¹⁾ mentioned that the replacement of wheat bran with different inert substrates in the artificial media of fruit flies led to an increase in pupals by 10% or more and a decrease in the size of pupae, which indicates that wheat bran contains some important nutrients for the growth of the reared larvae.

⁽¹²⁾ indicate that during his study of B. zonata rearing on four modified food media; it was found that the solid artificial media (B) gave the shortest development period for the larval stage 4 and 5 days on Hawaiian liquid media, while it was 6 days on a Mauritian liquid media.

These results also agreed with ⁽¹²⁾ which used wheat as a instead of yeast used in feeding the larvae. It proved its success in stimulating biological, chemical and biological characteristics, which can be considered as a food supplement.  found that feeding fruit flies in the larval stage is very important quantitatively and qualitatively, not only as a source of energy and the preparation of nutrients necessary for growth, development and survival, but also necessary for food storage in the pupae stage.

It was clear from the results that there is a clear effect for the type of media that used in rearing on the duration of the pupae, as these results agreed with ⁽¹³⁾ that the host plants are a very important factor that affects the biological aspects of the peach fruit fly.

Effect the media on the numbers of pupae and adults, the percentage of emergence and sexual ratio

The results that recorded indicate the effect of the treatments represented by the type of media that used to rear larvae on the rate of pupae counting. The highest rate of pupae was recorded in the treatment in which the artificial media was used, which amounted to 170.00 pupae, which is significantly different from the other treatments. The treatment of local orange fruits occupied the second stage to record the highest rate of pupae, at 96.70 pupae, which was also significantly different from the rest of the treatments. The emerging adults reached 154.3 adults in the artificial media treatment, followed by the treatment of local orange fruits, which recorded 85.00 adults, while the local Citrus fruits recorded the lowest rate of adults reaching 9 adults in the treatment. Percentage of emergence of adults was 74.86% in the mandarin treatment and there were no significant differences with other treatments (Table 2).

It was clear from the results that the type of artificial media that was used in rearing B. zonata had a clear effect on the rate of the pupae. The treatment of the artificial media recorded 170.00 pupae, which was significantly different from all other treatments, followed by the treatment of local orange fruits, while the lowest rate of the pupae number was 12.00 pupae. The type of artificial media that used in rearing had an effect on the rate of numbers of emerging adults, the highest rate was 154.3 adults in the treatment in which the artificial media was used, followed by the treatment of local oranges, and the lowest rate of the numbers of emerging adults was 9 at treatment of the local bitter orange fruits. The results also showed that the percentage of adult emergence was affected by the type of artificial media. The highest percentage recorded in the treatment used for the artificial media was 90.76% (Table 2). 

Table (2): Effect the type of artificial media on some biological indicators of the peach fruit fly B. zonata in laboratory at a temperature of 25 ± 2 °C.

* LSD for the treatments =15.36

* LSD for the period of development = 13.30

* LSD for the interaction between the treatments and the period of development = 26.60

The study showed that there is a relationship between the type of host, the size of the pupae and the rate of numbers of emerging adults.  Above results indicated the life of the peach fruit fly B. zonata was affected by the quality of the rearing media. It was noted during the performance of the experiment that there were clear differences on the growth, shape and size of the pupae. It is dark brown from the edges and the middle is golden. As for the pupae resulting from rearing on the artificial media, they appeared to be lighter in weight and with a light brown color. These differences can be attributed to the high-water content in the fruits and the content of these media on the content of carbohydrates and proteins. It is necessary for the development and growth of the larvae with laboratory conditions. It is also represented by a temperature of 25 ± 2 ° C and a humidity of 50 ± 5%.

It can conclude that the rearing medium has a great role in the growth period. The development of the immature stage and all the life indicators of the peach fruit fly B. zonata affected in terms of the number of pupae, the size and the shape of the insect. The peach fruit fly has the ability to infect different types of citruses. These results were agreed with (¹⁴⁾, it was mentioned that fruit flies can infect different plant families and under conditions that directly affect them, including temperature, rain, and the availability of plant hosts, and these factors affect the presence and distribution of the population density of fruit flies.

⁽¹⁵⁾ mentioned that in his laboratory study to determine the preferred plant hosts for laying eggs, in which ten types of natural fruits were used (apples, bananas, grapes, guava, mango, orange, papaya and pear). Based on the highest productivity of the pupae, which ranged 110.3 pupae/fruit, the mango was recorded as the most sensitive host for B. zonata. ⁽¹⁶⁾ found that mango is the most preferred host for the peach fruit fly. It recorded 318 pupae/fruits under conditions of free selection, while it has been 434 pupae/fruits when there was no chance of selection. ⁽¹⁷⁾ used more than one type of fruit (guava, apple, mango, citrus) to study the impact of these types of plant hosts on the Mediterranean fruit fly (Medfly) and the peach fruit fly fly in all life stages and under laboratory conditions where the two species were equal in effect with slight differences.

⁽¹⁸⁾ used different types of fruits. They found that the highest rate of the number of pupae was on guava fruits, which amounted to 125.34 pupae/fruit, and the lowest number on apples, which ranged 34.27 pupae/fruits.

It was also mentioned that the highest percentage of adult emergence was found on guava fruits compared to citrus fruits. ⁽¹⁹⁾ mentioned that the highest percentage of adult emergence was recorded on apple fruits. ⁽²⁰⁾ also mentioned that the use of wheat with the artificial diet led to a high increase in the rates of egg hatching, larval and the emergence of adults in the first generation.     Food type that used to feed the larvae of the peach fruit fly has been affected on the average numbers of both males and females. The highest rate of the number of females was recorded in the artificial media treatment, which amounted to 84.67 females, and this treatment recorded the highest rate of males and adults, which ranged 69.67 male. The treatment of local orange recorded the highest rates compared to the rest of the natural treatments, where the average number of females was 47 females, and the average number of males was 34.67 males, while the treatment of the fruits of the mandarin recorded 8.67 females and 5.33 males, however, the treatment of citrus fruits recorded different rates of male numbers. It reached 6.33 males and 2.67 females. The treatment of the artificial media and the natural fruits were superior in the rate of numbers of females over males. This indicates the effect of the media on the numbers of females and males of the peach fruit fly insect (Figure 1).

Figure (1): Effect type of media on the average number of females and males of the peach fruit fly B. zonata.

This is because of the difference in the nutritional, protein and carbohydrates values, and the appropriateness of the artificial media in terms of the amount of PH. The large size of the fruit and its high-water content to complete the metabolic process and the necessary protein, which made it a suitable environment for hatching eggs and developing larvae. ⁽²¹⁾ have been studied to find out the preferred media for the insect among several fruits in the Lab. They used oranges, apples, bananas, and squash and bitter squash vegetables. The results found that squash is the preferred host of vegetables. As for the fruit, bananas were the preferred host, followed by oranges, then apples and pumpkin. 

They mentioned that it needs to evaluate the host plants for this type of flies in order to achieve effective control. The study also confirmed ⁽²²⁾ where it showed that the host plant or medium play important roles for the larvae development. The preferred host should be high quality in providing the appropriate, basic and appropriate elements for the development of fruit fly larvae. 

Figure (2) indicates the effect of the type of media on the sex ratio of the fly insect B. zonata. The results showed that the treatments in which the fruits of the mandarine (Clementine), the local orange and the artificial media were significantly different in the percentage of females. The sex ratio in these treatments was (females: males) (1.69:1), (1.33:1) and (1.23:1) respectively, while the treatment in which the fruits of the local bitter orange showed that the ratio of males to females was (1:2.37). 

Figure (3-2): Effect the type of media on the sexual ratio of the peach fruit fly B. zonata

The study concludes that the sexual ratio of the peach fruit fly was superior to the proportion of females than males in all treatments, except the treatment of local bitter orange fruits, which showed superiority to males. The reason for this may be due to the inappropriateness of this host to rearing PFF. These results can be used in integrated management programs (IPM) of B. zonata. The results agreed with ⁽¹⁶⁾ of their study to determine the preferred hosts for laying eggs of the peach fruit fly in the conditions of free and limited selection under laboratory conditions. The data related to the sexual ratio were significant differences. It was noted that the maximum percentage of males in the treatment of pear fruits, which amounted (48.55%), while the treatment of apple fruits recorded (54.59).

Conflict of Interest: No

Funding: No funding sources

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