Study On The Occurrence Regulation Of Bactrocera Dorsalis(Hendel)in The Major Persimmon Producing Areas Of Guangxi

Bactrocera dorsalis(Hendel)is an important pest that severely damaged the fruit and vegetables in the main persimmon producing areas.In order to reveal the occurrence regularity and provide a theoretical basis for the comprehensive control of B.dorsalis in the main persimmon producing areas,the occurrence and overwintering characteristics of B.dorsalis were studied by combining field investigation and laboratory experiments.The main results were as follows(1)Different fruit trees constituting regions of the main persimmon producing area(Gongcheng County)presented different occurrence regulations of B.dorsalis.In Huayu village,there were 19 main kinds of fruit,but only Yellow peach,nectarine Zhongyou 5,Waxberry,Sanhua plum,Nai plum,Furong plum,Jujube,Persimmon,Hawthorn and Shatangju were damaged by B dorsalis.The occurrence regulation of B.dorsalis in Huayu village during the year were as follows:Peaches(Yellow peach and No.5 of nectarine)were damaged in late May ?Waxberry in early June? Sanhua plum and Nai plum in late June ?Nai plum and Furong plum in early July?Furong plum and jujube in late July?Jujube and Persimmon in early August?Persimmon from late August to October merely ?Persimmon and Hawthorn in November?Persimmon and Shatangju in December ?Persimmon in early January of the following year.In the Lianhua village where fruit trees were relatively less planted,there were 13 main kinds of fruit,but only Nai plum,Pear,Jujube and Persimmon were damaged by B.dorsalis.The occurrence regulation in Lianhua village were as follows:Nai plum in late June? Nai plum and Pear in early Julyv?Jujube and Pear in late July?Jujube in early August ?Persimmon from late August to early January of the following year.(2)From March 2018 to March 2019,Methy-leugenol was used to monitor the occurrence dynamics of the B.dorsalis males in the field.The results showed that the B.dorsalis males could be trapped in the whole year in Huayu village.The occurrence peak of B.dorsalis in different host orchards counted 2-6 times and which most orchards counted 4-5 times.The nurmber of B.dorsalis male adult was extremely low from late January to early May,with only 9 males were trapped from late February to early March.The population of B.dorsalis gradually increased in late May and the first peak occurred in late June.The occurrence peak of B.dorsalis was from late June to early December and the last peak was in early December.Then the population decreased sharply after late December.In each affected host orchard,the population of B.dorsalis increased along with the maturity of the host.The male of B.dorsalis could be trapped all year round in Lianhua village.The B.dorsalis population remained at an extremely low level from late December to early June of the following year.For example,only one male adult of B.dorsalis was trapped in persimmon orchard in early March.The population increased significantly in late June and the first peak of B.dorsalis population occurred in early July and the period of higher occurred of B.dorsalis from late June to early December and the last peak of B.dorsalis was in early December.After late December,the B.dorsalis population decreased sharply.(3)There were the selective taxis difference of laying eggs and larva feed of B.dorsalis among different host species at the same time.In early May,the oviposition selection order of B.dorsalis for five kinds of local fruit was as follows:Yellow peach>Qingxue nectarine>No.5 of nectarine>Baiyu nectarine>Taiwan nectarine.In late May,the oviposition preference order of B.dorsalis for five kinds of local fruit was as follows:Baiyu nectarine>Yellow peach>No.5 of nectarine>Waxberry>Taiwan nectarine.In late July,the oviposition preference order of B.dorsalis for five kinds of local fruit was as follows:Pear>Furong plum>Wampee>Grape>Chili.In early August,the order of oviposition preference of B.dorsalis for three kinds of local fruit was as follows:Wampee>Ginkgo>Jujube.In late September,the order of oviposition preference of B.dorsalis for two kinds of local fruit was as follows:Persimmon>Passion fruit.In late November,the order of oviposition preference for four kinds of local fruit was as follows:Persimmon>Shatangju>Hawthorn>Passion fruit.B.dorsalis laid significantly more eggs on the same kind of fruit with higher different maturity.For example,on yellow peaches,the average number of laid eggs by B.dorsalis on yellow peaches with red peel was 113.00 eggs at most,while on yellow peaches with cyan peel was only 14.00 eggs.On persimmons,the average number of laid eggs by B.dorsalis on yellow ripe fruit was 49.00 eggs at most,slightly less than 48.50 eggs with red ripe fruit and B.dorsalis did not lay eggs on cyan persimmons.The amount of laid eggs by B.dorsalis on different sizes of fruit of the same species varied from host to host,and not all of them increased with the growth of mature host fruit.For example,the eggs the big yellow peach fruit,the middle fruit and the small fruit was 298.67 eggs,264.33 eggs and 124.00 eggs,respectively,while the amount on the big persimmon fruit?medium fruit and small fruit were 111.25 eggs,116.00 eggs and 53.50 eggs,respectively.(4)Field trapping was carried out with yellow plates.The results showed that two species of fruit flies were trapped in Huayu village,namely B.dorsalis and Bctrocera tau(Walker),among which B.dorsalis was the dominant species.Three species of fruit flies,B.dorsalis,B,tau and Bactrocera cucurbitae(Coquillett),were trapped in Lianhua village,of which B.dorsalis was the dominant species.(5)B.dorsalis overwintered mainly by adults and pupae in the main persimmon producing area.The pupae in persimmon orchard distributed in the soil and fruit(the side contacting with soil).The pupae in the soil mainly distributed in the depth of 0-5 cm.The number of pupae in the soil near of the root and in the middle of the crown was significantly higher than that in the water falling part of the crown.It indicated that the soil near of the root and in the middle of the crown was more conducive to pupation of B.dorsalis.After winter,the survival rate of B.dorsalis pupae near the root and crown of the tree were 41.00 ± 4.82%and 31.60 ± 3.67%,respectively with no significant difference.The pupation rate of B.dorsalis in late December,late January and late February was 33.83 ± 5.47%,45.11 ± 3.56%and 42.11 ± 3.06%respectively and there was no significant difference among them.