Population Dynamics,Emigration And Infestation Regulations Of Bactrocera Dorsalis (Hendel) In Major Plum Production Areas Of Hezhou City

In recent years,with the adjustment of the agricultural structure in Hezhou,the planting area of plums has been expanding.The abundant host resources and the pleasant climate environment have provided favorable growth and reproduction conditions for Bactrocera dorsalis(Hendel),leading to an increasing risk of the insect disasters in Hezhou.Under these backgrounds,this paper combined field sampling with lab experiment to explore the occurrence,emigration and infestation,and behavioral reaction of B.dorsalis in major plum production areas of Hezhou successively.Below is a summary of major research results and conclusions:(1)In the major plum production area of Hezhou city,the male B.dorsalis in major orchards can be traped by two kinds of traps which are attractive bottle and yellow sticky cards.The B.dorsalis trapping reached a peak in the concentrated maturation period of fruit from the first half of July to the lasthalf of September.Besides,correlation analysis was conducted on the population fluctuation pattern and meteorological factors of different orchards in the same period.These results indicated a significantly positive correlation between three kinds of temperature factors and the population dynamics of B.dorsalis.Based on the above analysis,it could be seen that major factors affecting the population dynamics of B.dorsalis included the maturity period of host fruits,area of fruit bearing and temperature.(2)In the major plum production areas,B.dorsalis infestation the first mature host fruits of the year-loquats and acid plum that began in the the latter half of the April..In May and June,the major host plants that suffered from the infestation were Sanyue plum(May)and Sanhua plum(June).Then,the emigration and infestation alternated among the host fruits,including grapes,peaches,wampees,and citrus fruits that subsequently entered the maturity period.Research showed that the last main infestation is the late harvest of autumn and winter fruits-sugar sugar orange and persimmon.The sequence and infestation degree of B.dorsalis in various host vegetables and fruits were related to the host species,maturity and picking period and occurrence quantity of B.dorsalis in the same period.There were two peaks of emigration and infestation of B.dorsalis in a year.The first phase was from June to July,with the main infestation targets being peaches and sanhua plums.The second phase was from September to October,with the main infestation targets being guavas.(3)In major plum production areas of Hezhou city,B.dorsalis were overwintering with pupae.The pupation amount in different orchards ranked in a descending order,namely Tribute orange > Sugar orange > Mashui oranges.The pupation amount in the canopy drip line was lower than that near to the tree root.The pupae were mainly distributed the range of 0?5 cm under groud,which accounted for 85.76 ± 8.10% ? 95.01 ± 4.80% of the total pupae,and the deepest pupa generation area could reach 8 cm below the land.(4)B.dorsalia exhibited the highest spawning preference in the yellowing period of plum in different maturities.The correlation analysis suggested that the spawning selection of B.dorsalis on different parts of plums with same maturity was significantly negatively correlated with fruit surface hardness.The B.dorsalis female preferred to oviposit on host plums with a low fruit surface hardness but high maturity.The research results suggested that the fruit surface hardness and colors were major factors affecting oviposition of B.dorsalis females.(5)The electroantennogram(EAG)and the Y-type olfactometer were used to measure EAG and orientation behavioral response of male and female adult B.dorsalis towards 11 volatile substances from plum.Results showed that EAG response waveforms of male and female adult B.dorsalis towards 11 volatile substances were obvious,and that their electrophysiological response rules of the same volatile substances atdifferent concentration gradients were similar.Specifically,the response relative value of high concentrations was significantly higher than the response relative value of low concentrations.Besides,EAG response of female and male adults B.dorsalis towards different volatile matters was significantly different.At specific concentrations,the stimulus response of female B.dorsalis towards the volatile matters,such as ethyl caprylate,butyl acetate and ethyl hexanoate were obvious,and the EAG relative response value was above 100%.Meanwhile,the response of male insects towards ethyl hexanoate and hexyl acetate were relatively obvious,with the EAG relative response value being above 80%.As to the smell-oriented response,the female and male adults of B.dorsalis showed the same tendency of selection of esters,such as ethyl butyrate,butyl acetate and leaf acetate,but the degree of their tendency was different.Futhermore,the analysis results showed that extractions of volatile matters of plums at different degrees of maturity were combined to indicate that esters,including ethyl caprylate and ethyl hexanoate,whose relative content in the mature plums was high were one of major factors resulting in preference of plums with a high degree of maturity for their oviposition among female adults of B.dorsalis.Therefore,the above esters can be adopted as basic components for in-depth research of the component screening of new-type attractant with the botanic source for B.dorsalis.