Studies On The Occurrence Regulation Of Bactrocera Dorsalis(Hendel)in The Citrus-and Mango-producing Areas

Bactrocera dorsalis(Hendel)is an important fruit and vegetable pest that has attracted worldwide attention.It has strong reproductive capacity,a wide host range,and is prone to outbreaks.It mainly causes fruit rot and fruit drop,which seriously affects fruit yield and quality.In this study,the occurrence regulation of B.dorsalis was used as the starting point,and the combination of field surveys and laboratory tests was used to determine the damage pattern of B.dorsalis in the citrus-and mango-producing areas and the factors affecting the emergence of B.dorsalis,the observation of the longevity and oviposition period of adult B.dorsalis and the oviposition options of the host B.dorsalis.The purpose was to reveal the occurrence regulation of B.dorsalis in these two producing areas in order to provide theoretical basis for comprehensive prevention and control of B.dorsalis in different producing areas.The main research contents and results were as follows:1.A systematic sampling investigation was carried out on the fruit of different orchards in the citrus-producing area(Guilin Lingchuan),there were 17 species hosts,they were:Shatangju,Chuntian orange,Nanfeng orange,Satsuma,Ponkan,Shatian pomelo,Sweet orange,Waxberry,Persimmon,Pear,Peach,Loquat,Raisins,Cucumber,Towel gourd,Bitter melon,Chili.Among them,7 species were found to be affected by B.dorsalis,there were Nanfeng orange,Satsuma,Persimmon,Waxberry,Loquat,Peach,Pear.There were two peaks of B.dorsalis in the region during the peak period of the year.The first time was from June to July,mainly affecting peaches and pears;the second time was from October to November,which mainly damages Satsuma,and the second damage was more serious.In the citrus-producing area from the end of December to the end of April next year,no B.dorsalis was found to harme,and the first infestation occurred in early May.The host was a cricket and the last time it was damaged in mid-December,the host was Satsuma.Before the main citrus fruits were attacked,the pears were attacked by B.dorsalis.In the citrus-producing area,five citrus varieties,Shatangju,Chuntian orange,Ponkan,Shatian pomelo and Sweet orange,were not harmed by B.dorsalis.According to the chronological order,the occurrence regulation of B.dorsalis in the citrus-producing area was:Loquat → Waxberry and Peach → Peach and Pear → Pear → Satsuma → Satsuma and Persimmon→ Nanfeng orange,Satsuma and Persimmon → Satsuma.2.A systematic sampling investigation was carried out on the fruit of different orchards in the mango-producing area(Nanning Wuming),there were 18 species hosts,they were:Nanfeng orange,Shatangju,Kumquat,Murcott,Wogan,Shatian pomelo,Tainongyihao mango,Sijimi mango,Guava,Waxberry,Pear,Loquat,Papaya,Tomato,Cucumber,Towel gourd,Bitter melon,Chili.Among them,9 species were found to be affected by B.dorsalis,there were Kumquat,Guava,Tainongyihao mango,Sijimi mango,Shatangju,Nanfeng orange,Waxberry,Loquat and Pear.There were two peaks of B.dorsalis in the region during the peak period of the year.The first time was from January to February,mainly affecting Guava,Shatangju and Kumquat;the second time was July,which mainly damages Tainongyihao mango,and the second damage was more serious.There were something be damaged by B.dorsalis every month in the mango-producing area,the hosts that were first killed in the year were Shatangju,Guava,Kumquat and Sijimi mango,and the hosts that were the last victims were also Shatangju,Guava,Kumquat and Sijimi mango.Before the main mango fruits were attacked,the loquats were attacked by B.dorsalis.In the mango-producing area,all mango varieties were harmed by B.dorsalis,but the damage of Tainongyihao mango was higher than that of Sijimi mango.According to the chronological order,the occurrence regulation of B.dorsalis in the mango-producing area was:Shatangju,Guava,Kumquat and Sijimi mango → Shatangju,Guava and Kumquat → Guava and Kumquat → Kumquat and Loquat → Loquat →Pear and Tainongyihao mango → Waxberry,Pear and Tainongyihao mango → Pear and Tainongyihao mango → Kumquat and Tainongyihao mango → Kumquat → Nanfeng orange and Kumquat → Sijimi mango,Nanfeng orange and Kumquat → Sijimi mango and Kumquat →Shatangju,Sijimi mango and Kumquat.3.The factors influencing the feathering of B.dorsalis were studied.The results showed that the different densities of sturgeons,different depths of soil,different soil qualities and different pH values had significant effects on the emergence rate,but the effect on the pupa period was not significant.Among them,the cormorative emergence rate and the diurnal period of the diffirent pupation positions were all different,the highest emergence rate was 97.33 ± 2.67%in the "Lie" position,and the lowest in the "Head downward" position was 78.00 ± 7.57%,the longest pupa period in the "Lie" position was 11.19 ± 0.52 d,and the shortest pupa period in the "Head of 45° inclined downward" position was 10.46± 0.09 d.The emergence rate and the pupa period of different soil depths were all different.The depth of the soil layer was 5 cm,the highest emergence rate was 96.67 ± 1.33%,and the emergence rate of the cormorants was the lowest at 9 cm,only 64.00 ± 15.87%.The soil depth was 5 cm,the shortest pupa period was 10.90 ± 0.20 d,and the longest pupa period was 11.02 ± 0.22 d at 3 cm.The emergence rate and pupa period of B.dorsalis in different soil textures were different.The emergence rate in clay was the highest at 96.00 ± 4.00%,the emergence rate in the loam was the lowest at 56.67 ± 3.71%,the pupa period of sandy and clay soil were longer at 10.44 ± 0.02 d,and the loam soil was the shortest at 10.26 ± 0.12 d.Both the emergence rate and pupa period of B.dorsalis in different pH soils were not the same.The soil pH=5.85 had the highest emergence rate of 51.33 ± 5.46%,the soil pH=9.98 had the lowest emergence rate of 16.67 ± 5.21%,the soil pH=8.38 had the longest pupa period was 12.13 ± 0.06 d,and the shortest pupa period was 11.73 ± 0.31 d when soil pH was 7.34.4.Feeding with artificial feed,B.dorsalis adults who had a temperature of 25 ± 1 ℃,a relative humidity of 70 ± 5%and a photoperiod of 14L:10D had an average longevity of 87.53 ± 1.82 d,which was significantly longer than the average longevity of male adults 82.17 ± 1.81 d;the average of the pre-oviposition period was 12.05 ±1.38 d,and the average of the oviposition period was 74.23 ± 23.04 d.5.The spawning options of B.dorsalis were studied:Select 10 local hosts in the citrus-producing area in late October as a combination,including Nanfeng orange,Satsuma,Sweet orange,Shatian pomelo,Persimmon,Raisins,Cucumber,Bitter melon,Towel gourd,and Chili were selected by the B.dorsalis in this combination.As a result,the eggs produced the highest number of eggs laid on the mandarins in Satsuma,reaching 784,and the spawning amount on the Towel gourd was the lowest,only 64.The specific preference of spawning selection was as follows:Satsuma>Nanfeng orange>Persimmon>Shatian pomelo>Sweet orange>Bitter melon>Chili>Cucumber>Raisins>Towel gourd.Select 10 local hosts in the mango-producing area in late October as a combination,including Wogan,Murcott,Kumquat,Shatian pomelo,Nanfeng orange,Papaya,Bitter melon,Cucumber,Towel gourd and Chili.The combination of spawning options resulted in the highest number of eggs spawned on kumquat,reaching 1,257 grains,and the least eggs on Cucumber were 390 eggs.The specific preference of spawning selection was as follows:Kumquat>Nanfeng orange>Wogan>Murcott>Shatian pomelo>Papaya>Towel gourd>Bitter melon>Chili>Cucumber.The regulation of preference for spawning of different levels of Shatangju and Sijimi mango for B.dorsalis was:Overripe>Medium maturity>Unripe.