Fund Project: Effect of Passion Fruit on the Growth and Development of Orange Fruit Fly

Fund Project: Effect of Passion Fruit on the Growth and Development of Orange Fruit Fly

Fund Projects: Guangdong Agricultural Development and Rural Work Special Fund Project (2017LM4172); 2018 Guangdong Provincial Rural Revitalization Strategy Special Fund Project (Passion Fruit Industry Risk Control and Countermeasure Research)

Liu Kaidi

Passion fruit is native to South America, also known as passionflower, Brazil fruit, egg fruit, is a perifloridae genus of evergreen climbing vines. China began to introduce the cultivation of passion fruit in 1913, and now Guangdong, Guangxi, Fujian, Taiwan and other places are widely cultivated, in 2017 Guangxi planted an area of more than 20,000 hm2, known as the hometown of passion fruit cultivation." With the expansion of passion fruit cultivation area, the problem of passion fruit diseases and insect pests has become increasingly prominent.

Bactrocera dorsalis Hendel belongs to the diptera fruit fly genus Tephritidae, is a world-important quarantine pest, can harm citrus, guava, star fruit, mango, banana, melon and other more than 40 families of more than 250 kinds of fruits and vegetables, seriously affecting the yield and quality of fruits and vegetables, the current orange fruit fly has been assessed as a high-risk pest. The female of the orange fly lays eggs in the fruit, and the hatched larvae eat the flesh of the fruit, causing the damaged fruit to rot and fall off. In addition, there are differences in the selection of fruits of different ripeness and different parts of the fruit, mainly affected by the volatile substances, quality traits, color and other factors of the fruit. Orange flies prefer to lay eggs on the peel of fruits such as bananas, starfruits, and mangoes when they are ripe. Orange fruit fly has differences in spawning options on the peel and pulp of ripe bananas, preferring to spawn on the pulp. Guava rotting fruit has a greater lumination effect on orange flies than ripe fruits, and ripe fruits have a greater lumination effect than green fruits and more ripe fruits

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Most of the research on the harm of orange fruit flies to passion fruit stayed in outdoor field surveys, and there were few studies on the effect of indoor passion fruit on the growth and development of orange fruit flies. In order to clarify the harm of orange fruit fly to passion fruit, this study explored the occurrence and growth and development of orange fruit fly on passion fruit through field investigation and indoor bioassay, in order to provide a theoretical basis for the pest control of passion fruit and the healthy development of passion fruit industry.

1 Materials and methods

1.1 Test materials

The larvae of the orange small fruit fly are reared in the artificial climate chamber of the Plant Health Innovation Research Institute of Zhongkai Agricultural Engineering College by artificial feed, the feeding temperature is (25±1) °C, the relative humidity is 50%~70%, and the photoperiod L (light) is D (dark) = 14 h:10 h. The passion fruit variety used for the experiment was purple incense, which was collected from the passion fruit planting base in Liangcun Town, Huaiji County, Zhaoqing City.

1.2 Test instruments

RQH-01Y artificial climate box was purchased from Huangshi Hengfeng Medical Instrument Co., Ltd.; electronic digital caliper-II. was purchased from Harbin Measuring Tools and Cutting Tool Group Co., Ltd.; PHB-1 portable pH meter was purchased from Shanghai Sanxin Instrument Factory; 0~50% sugar meter was purchased from Shanghai Lichen Instrument Technology Co., Ltd.

1.3 Methods

1.3.1 Field Hazard Investigation of Passion Fruit by Orange Fruit Fly From May 2018 to December 2019, whether passion fruit in Guangxi (Guilin), Guangdong (Guangzhou, Zhaoqing, Meizhou, Huizhou, Shaoguan, Jiangmen, Heyuan) and other places was investigated whether passion fruit was harmed by orange fruit flies. In the passion fruit planting base of Liangcun Town, Huaiji County, Zhaoqing City, Guangdong Province, 40 mesh mesh mesh was used to cover the passion fruit plant, and 40 orange small fruit flies (hermaphrodite ratio was 1:1) were released in the net, and the harmful phenotype of orange small fruit fly to passion fruit was observed, and it was clear whether orange small fruit fly layed eggs on passion fruit. At the same time, the trap bottle containing methyl eugenol is hung in the orchard to trap the fruit flies (1 ligant bottle is suspended every 20 m2 for a total of 10 hanging; the attractant is changed every 2 weeks, and the orange fruit fly is collected at the same time as the trap is changed), and the number of orange fruit flies trapped is recorded.

1.3.2 Observe the spawning, pupaeing and feathering of orange flies on passion fruit 10 purple green fruits (immature fruit after 20 days of flowering, green skin, white flesh) into a cage containing 60 orange fruit fly (1:1 male-to-female ratio) (length 45 cm, width 45 cm, height 65 cm), every 8 h remove passion fruit to see if there are any egg laying marks. The test is set up for 3 replicates. After 48 h, passion fruit with egg laying traces of orange flies in the cage is transferred into the sandbox sand of the artificial climate box (the thickness of the sand table is about 30 cm), and the sand table is covered with insect nets to prevent other insects from flying in, and the sand soil is kept moist during the period. After 10 d, turn the sand table sand soil daily to observe and record the number of orange small fruit fly pupae. When adults appear, observe and record the number of adult orange flylets daily.

1.3.3 Passion fruit in different ripening states for the growth of orange small fruit fly larvae

The influence of development according to the number of flowering days and the color of the peel divides passion fruit into 3 mature states: young fruit (small fruit within 10 days after flowering, the skin is green, the pulp is not yet developed or has just begun to develop), green fruit, mature fruit (the skin is purple, the flesh is orange-red). The above three mature passion fruit are tested according to the peel, pulp, peel + pulp. At the same time, to prevent the juice in the pulp from drowning the larvae, paper towels are added to the pulp. Measure the pH and sugar degree of the ripe fruit with a pH meter and a glycycometer, respectively, and repeat the test 10 times.

The experimental settings are as follows: the mature fruit and green fruit treatment groups are equipped with peel group, pulp group and peel + pulp group, respectively, and the young fruit pulp is not developed and therefore only set to the peel group 1 group, and the control group is banana. Each treatment is set to repeat 3 times. 30 orange fruit fly eggs are evenly distributed over each treated fruit. Put the above treated passion fruit into (25±

1) °C artificial climate box, observe and record the hatching of orange small fruit fly eggs every day, after the eggs hatch into larvae and the larva pupates, the pupal length is measured by eyepiece micrometer under the binocular asana microscope, and the pupal pupal rate is calculated daily, until all pupae feathers become adults, and the pupa feathering rate is counted.

1.4 Data Analysis

Use Microsoft Excel 2016 and SPSS 17.0 software for data statistics and analysis. Duncan's new compound deviation method was used for difference significance analysis.

2 Results and analysis

2.1 Harm of orange fruit fly to passion fruit

Field surveys found that live adult orange flies were found in passion fruit plantations everywhere (Figure 1), most of which rested on the back of the leaves. Field shroud observation found that orange small fruit fly mainly in the wound or gap of the victim passion fruit lay eggs, the victim of the young fruit developed into a deformed fruit, the skin is commonly filled with small holes, the mature fruit victim site is crater-like convex, the victim part can not be normally colored, the peel is cut open, the lesion traces can be seen, but the flesh is intact (Figure 2), indicating that the fruit fly larvae have not yet decayed into the flesh site, and 51.7% of the victim fruit victim sites have found fruit eggs (Figure 3).

Fig. 1 Adult orange fly resting on the back of passion fruit leaves

Fig. 2 Ripe passion fruit is affected by the symptoms of orange fruit fly

Fig. 3 The harm of orange small fruit fly to passion fruit

A. Symptoms of harm caused by orange fruit fly on passion fruit; B. Eggs laid by orange fruit fly on passion fruit

The number of male adult orange fruit fly traps in passion fruit orchards from July 6 to October 28, 2019 is shown in Figure 4, of which the smallest number of male adult orange fruit fly was trapped on July 20, 2019 (4.0 heads/bottle), and the highest number was on September 16, 2019 (19.3 heads/bottle).

Figure 4 The number of orange flies in the passion fruit orchard from July 6 to October 28, 2019

2.2 Growth and development of orange fruit fly on passion fruit

Adult orange fruit fly has spawning phenomenon and egg laying marks on passion fruit (Figure 5), and a total of 13 passion fruit have egg laying marks after 48 h, accounting for 43.3%. The average number of spawning marks is 1.73 per fruit. After 10 days, the sand table was turned over daily to count the number of orange small fruit fly pupae, and a total of 52 orange small fruit fly pupae were examined. After full observation, a total of 49 pupae feathers turned into adult insects, of which 28 were females (57.1%) and 21 males (42.9%), with a pupal pupal rate of 94.2%.

Fig. 5 Female adult orange fruit fly lays eggs on the young fruit of passion fruit

2.3 Effects of passion fruit of different ripeness on the development of orange fruit flies

Based on the evaluation indexes of the length, pupal rate and feathering rate of the orange fruit pupae, the development of the orange fruit in different mature states on the fruit of the purple passion fruit was studied, and the results were shown in Table 1.

From Table 1, it can be seen that the orange fruit fly cannot complete pupal development on the peel of the ripe fruit of passion fruit, and the remaining groups of treatments can complete the entire life history. In addition to the mature fruit peel group, there was no significant difference in pupa length between the pupae length of the mature fruit pulp group, the ripe fruit peel + pulp group, the green fruit peel group, the green fruit peel group, the green fruit peel + pulp group, and the young fruit peel group.

Compared with the control banana group, the pupal pupalization rate and pupal feathering rate of orange small fruit flies fed at different ripening stages and different fruit sites of passion fruit significantly decreased. The pupal rate and feathering rate of the young fruit peel were the lowest, among which the pupal rate of the young fruit peel t=26.5, df=4, P<0.001, feathering rate t=21.1, df=4, P<0.001, green fruit peel pupal rate t=31.5, df=4, P<0.001, feathering rate t=20.2, df=4, P<0.001, there was no significant difference between the two, all significantly lower than the banana group. In the green fruit treatment group, the pupal rate and feathering rate of orange small fruit fly in mixed rearing (peel + pulp) were significantly higher than those in the peel group, the pupae rate of pulp group t=27.3, df=4, P<0.001, feathering rate t=22.5, df=4, P<0.001, peel + pulp group pupal rate t=33.2, df=4, P<0.001, feathering rate t=24.1, df=4, P<0.001. In the mature fruit treatment group, there was no significant difference between the pupal rate and feathering rate of orange small fruit fly mixed with pulp and peel pulp. The above results show that although the orange fruit fly can complete the life history on passion fruit, there are differences in the growth and development of orange fruit fly raised in different parts of passion fruit.

In the pulp treatment group, the pupal rate of mature fruit and green fruit-reared orange flies was not significant, but the feathering rate of orange flies raised with green fruit pulp was significantly higher than that of orange flies raised on mature fruit pulp (t=23.8, df=4, P<0.001). In the mixed breeding group of pulp and peel, there were no significant differences in pupalization and feathering rates of orange flies raised with mature fruit and green fruit. For young fruits, because their pulp has not yet developed, the orange fruit fly raised with young fruit is equivalent to the orange small fruit fly raised with young fruit peel, and the results show that the orange fruit fly fed on the passion fruit peel in 3 developmental states has a significantly lower pupal rate and feathering rate than other treatment groups, and the orange fruit fly on the mature passion fruit peel cannot complete the entire life history.

In addition, the sugar content and pH of ripe passion fruit and control bananas were determined, and the results (Table 2) showed that the sugar content of passion fruit was 16.0% to 19.3%, the average sugar content was 17.72%, and the sugar content of the test banana was 19.1% to 23.7%, and the average pH was 20.77%. The pH of passion fruit is 1.50 to 1.95, the average pH is 1.78, and the pH of the test banana is 6.50 to 6.95, and the average pH is 6.80. The sugar content and pH of the control bananas were significantly higher than those of ripe passion fruit (sugar content: t=17.3, df=4, P<0.001; pH: t=20.6, df=4, P<0.001).

Table 1 Effects of passion fruit on the growth and development of orange flies

Note: Different lowercase letters after the same column of data indicate significant differences (P<0.05). The same applies below

Table 2 Sugar content and pH of passion fruit and control bananas

Note: Different capital letters after the same column of data indicate significant differences (P<0.01)

3 Discussion

Passion fruit is currently mainly distributed in tropical and subtropical regions such as south china and southwest China, which are suitable distribution areas of orange small fruit fly. Field investigation reports have shown that orange flies occur in passion fruit orchards. Similarly, the results of this study's field findings and field shroud tests show that passion fruit can be infested by orange small fruit flies. The insect olfactory system can recognize specific chemical odor molecules and has an important impact on processes such as insect feeding and spawning. The pest tendency of the orange fruit fly is related to the type, part and ripeness of the fruit. Siderhurst et al. have found that female orange fruit fly females have a tendency towards mixed volatile substances of olive trees. Shi Wei et al. tested the tendency of orange fruit flies with the volatile odors of 3 fruits and 3 ripe mangoes, and proved that orange flies have tendencies and selectivity for the volatile odors of fruits. Chen Sichang's study found that 8 volatiles in guava have different degrees of luring effect on orange small fruit flies, including n-hexanol, ethyl acetate, ethyl butyrate, hexyl acetate, and leaf alcohol. Chen Qing et al. detected that the volatiles of purple passion fruit juice contained 81 compounds such as n-hexanol, ethyl acetate, ethyl butyrate, hexyl acetate, and foliol. Therefore, it is speculated that the volatiles of passion fruit contain compounds that have an attractive effect on orange fruit flies, and it is further speculated that orange fruit flies have a large-scale risk of harm in passion fruit orchards. In addition, field investigations found that orange fruit flies mainly lay eggs at the wounds or places with gaps in the wounds of the victim passion fruit, which is consistent with the results of Xie Qi et al.,, who found that the female orange fruit fly prefers to lay eggs in the fruit wound area, depression site, and gap area.

The results of this study show that the orange fruit fly cannot complete the growth and development on the ripe fruit peel of the purple passion fruit, which may be related to the fact that the ripe passion fruit peel is extremely prone to water dryness and cannot meet the water and nutrients required for the growth and development of the orange fruit fly. Even for young fruits and immature green fruits, the feathering rate of orange fruit flies on different parts of these two types of fruits was significantly lower than that of banana control groups, indicating that passion fruit was not the most suitable host for orange fruit flies, and that different parts of passion fruit and passion fruit in different mature states had different effects on the growth and development of orange fruit flies, which was basically consistent with the research results of Hu Hanqing and others.

It has been found that the growth and development of orange fruit fly is affected by the sugar content and pH of the fruit, and the harm of orange fruit fly to the same fruit is more inclined to those with higher sugar content. Panya studies have shown that the concentration of sugar in artificial feed affects the hatching rate of orange small fruit fly eggs and larvae and the quality of old mature insects. When orange flies are continuously reared with artificial feed with 20% sugar concentration for 4 generations, the hatching rate is significantly higher than that of orange flies raised with artificial feed with sugar concentrations of 12%, 16%, 24% and 28%. The pH of the fruit can affect the feathering rate of the orange fruit fly. Fu Yousheng et al. have found that the pH of guava expansion is 5.0 to 5.5, which is conducive to the feathering of orange flies, but when the pH is greater than 5.5 or less than 4.0, it will lead to a decrease in the feathering rate of orange flies, especially when the pH is less than 4.0, the feathering rate drops to the lowest. In this study, the glycosity and pH of ripe passion fruit and control bananas were measured, and the results showed that the average sugar content of passion fruit was 17.72%, and the average sugar content of bananas for test was 20.77%. The average pH of passion fruit is 1.78, the average pH of the bananas tested is 6.80, and the sugar content and pH of passion fruit are not within the suitable range of normal growth and development of orange fruit fly, so it is speculated that the difference in sugar content and pH between passion fruit and banana may be one of the reasons for the decrease in the growth fitness of orange fruit fly.

In this study, the peel thickness of ripe passion fruit and the length of the egg laying needle of orange fruit fly were measured, and the average thickness of mature peel was (35.24±4.00) mm, and the length of the egg layer (basal node, shrinkage membrane, egg laying needle) was (36.10±0.17) mm. Studies have shown that the shrinkage membrane and egg-laying tubes of the orange fruit fly may enter the fruit, therefore, theoretically, the orange fruit fly can lay eggs inside the purple passion fruit, but the field survey results show that the orange small fruit fly likes to lay eggs on the young fruit as the pest, as the fruit grows, the egg laying hole gradually becomes larger, and the peel appears the symptoms of the orange small fruit fly larvae, but no insect body is found in the fruit. For the above results, it is speculated that the high hardness of the peel of passion fruit and the sugar content of the peel are not suitable for the development of orange fruit fly eggs, which is one of the reasons why the orange fruit fly larvae cannot reach the pulp part.

In summary, the results of field surveys and indoor measurement tests show that orange small fruit flies can harm passion fruit and can complete growth and development on passion fruit. Different parts of passion fruit and passion fruit in different mature states have different effects on the growth and development of orange fruit fly, and orange small fruit fly cannot complete growth and development on the peel of ripe passion fruit, but can complete life history on mature fruit flesh, green fruit and young fruit. The results of sugar content and pH determination test showed that although orange fruit fly can complete life history on passion fruit, passion fruit is not a suitable host for orange fruit fly. Since the orange fruit fly can complete the life history on the passion fruit, and in view of the long fruiting period of passion fruit, the passion fruit may become a transitional place for the orange fruit fly after the harvest of other fruits and vegetables is completed.