Oversummering And Overwintering Biology Of Bradysia Odoriphaga And Green-control Techniques Of The Pest

Bradysia odoriphaga Yang et Zhang,commonly known as chive maggot,is a major biological disasters which restricting the development of Chinese chives industry.B.odoriphaga is a kind of peculiar vegetable underground pest in China,which was researched lately in domestic,and still blank abroad.Even the basic biological characteristics on B.odoriphaga were not clear enough,it brought great difficulties to the prevention and control work.Currently,farmers mainly use chemicals to control B.odoriphaga,even apply high toxic pesticides banned on vegetables,causing food poisoning when eat leeks and lasting damage to farmland ecosystem.For an economic,practical,green pollution-free method against B.odoriphaga,we studied on the law of population dynamics in field,the biological characteristics on over-summering and over-wintering,and disaster mechanism.And then we screened pesticides,application methods,application periods,and new techniques of physical control.In addition,for the molecular mechanisms on over-summering,over-wintering and disaster,etc.,we researched reference genes in B.odoriphaga to calibrate the target genes.The main research conclusions in this article are as follows:?1?Confirmed the population dynamics and the space distributing character of B.odoriphaga in fields.B.odoriphaga has three to four generations in chive fields annually but is harmful all the year round in greenhouses in Beijing area,and the hazard summit period is in spring and autumn.The peak of adults is from April to May.Adults and larvae are very rare from July to August,gradually increase in September,and October is the peak period again.B.odoriphaga adults can't be found in open field in winter,but can be found in greenhouses.B.odoriphaga adults mainly acts close to the ground.B.odoriphaga eggs,larvae and pupas are mainly distributed in soil at a depth of 0-5 cm.?2?Clarifiedthe over-summering and overwintering biological characteristics.B.odoriphaga was predominantly found in local chive fields in summer.The population of B.odoriphaga in summer was generally low,but was positively related with soil humidity.Larvae mainly hide in leaf-sheath or soil under high soil humidity.However,they mainly hide in bulbs,roots or false stem when the soil was droughty.B.odoriphaga chiefly overwinter as 4th instar larvae about90.78%,inside chive bulbs or in soil,while other stadiums averaged about 9.22%.?3?Screened high efficiency and low toxicity pesticides,and presented scientific and reasonable application methods and application periods against B.odoriphaga.The efficiency of different insecticides against B.odoriphaga on 28th day was Clothianidin,Thiamethoxam,Imidacloprid,Hexaflumuron,Dinotefuran?Phoxim?Lufenuron,Cyromazine.The control efficiency of various application methods against B.odoriphaga was'twice root-irrigation'?'fixed-point spray'?'conventional root-irrigation'.The techniques that'controlling pests in summer to reduce pests damage in autumn'and'controlling pests in winter to reduce pests damage in spring'had favorable control efficiency against B.odoriphaga.Chinese chives were harvested without pesticide residue.Therefore,the techniques that'twice root-irrigation','controlling pests in summer to reduce pests damage in autunm'and'controlling pests in winter to reduce pests damage in spring'are worthy to be recommended to control B.odoriphaga.?4?Invented the technology of combiningO₃ water with films?short for COF?against B.odoriphaga;revealed the effect of ozone water on the growth and seed germination for Chinese chives.O₃ water irrigated in open fields had no obvious control efficacy on B.odoriphaga,but covered with plastic film had significant control efficacy.O₃ water led to malformation or death of adults,larvae and pupae.O₃ water promoted the early growth of Chinese chives,increased the plant height,but was not conducive to germinate new roots again after fibrous roots clipped.When the seeds of Chinese chives were soaked with O₃ water and then washed instantly with clean water,they normally germinated.Therefore,ozone water against B.odoriphaga is worthy to be recommended under closed environment.?5?Invented creatively the new technique of soil coated with plastic films and exposed to the sun?short for SFS method?against B.odoriphaga;cleared the mechanism and the optimal condition for using SFS method against B.odoriphaga.After coationg film under strong sunlight for one day,the control efficiency against B.odoriphaga was high as 100%.The yields of Chinese chive of treatment groups showed no significant difference compared with control group after 20 days.Four stages of B.odoriphaga?adults,eggs,larvae,and pupas?,were dead at a constant temperature of40?for 1.33 h,1.83 h,2.83 h and 3.67 h,respectively;while at 44?only for 0.50 h,0.83 h,1.33 h and 1.50 h,respectively.Both adults and eggs were more sensitive to temperature compared with larvae and pupas.Wathet anti-dripping film of 0.12 mm thickness was the optimal to increase soil temperature;when the height of square frame covered plastic film was 30 cm,soil temperature was the highest,and the time of keeping the soil temperature over 40?was maximum.?6?Screened suitable reference genes in B.odoriphaga to calibrate the expression of functional genes,laid a foundation of the related molecular mechanism on over-summering,overwintering,and high temperature lethal effect,etc.The most appropriate sets of internal controls were RPS15,RPL18,and RPS18across developmental phases;RPS15,RPL28,and GAPDH across temperatures;RPS15and RPL18 across pesticide treatments;RSP5,RPS18,and SDHA across photoperiods;ACTb,RPS18,and RPS15 across diets;RPS13 and RPL28 across populations;and RPS15,ACTb,and RPS18 across all samples.According to the population dynamics,over-summering and over-wintering biological characteristics of B.odoriphaga,this study had invented'twice root-irrigation','controlling pests in summer to reduce pests damage in autumn'and'controlling pests in winter to reduce pests damage in spring','COF technology',and'SFS method',and so forth against B.odoriphaga.In addition,screened suitable reference genes in B.odoriphaga,which laid a foundation of the related molecular mechanism on over-summering,over-wintering,and high temperature lethal effect,etc.Especially,based on biological characteristics that B.odoriphaga could not endure high temperature,we had invented creatively the new technique of soil coated with plastic films and exposed to the sun?short for SFS method?against B.odoriphaga.The control efficacy of SFS methods in multiple regions?Beijing,Tianjing,Hebei,Shangdong,Anhui,Zhejiang,Gansu,etc?were as high as 100%.Meanwhile,the demonstrating conference on SFS method against B.odoriphaga was held on July 5th,2017 in Shouguang,Shangdong province.Several experts and the relevant leader of planting industry department,the ministry of agriculture regard SFS method as a green,economic,simple,practical revolutionary new technique against the root-feeding pests,and is also the model of ecological control technique for pests.They suggested publicize and popularize the SFS method widely,which will provide new idea for controlling soil diseases and pests on other vegetables.