Biological Characteristics Of Bradysia Odoriphaga And Pesticide Screening

Bradysia odoriphaga is a endemic pest species to China, the larvae cluster damage Leek root, causing Leek seedlings death, serious damage can result in total destruction, has become the main limiting factor of leek production. This insect has a habit of submerged hazards, and its occurrence regularity and study on biological characteristics of weak, leading to forecast and control technique of lagging, once began damaged is difficult to control in production, often use large doses of highly toxic pesticides filling the root, not only caused excessive pesticide residues in soils and leek, poses great threat to human health and the environment, but due to continuous heavy use of pesticides causes its resistance. Therefore, research supplement biological characteristics of Bradysia odoriphaga, looking for pollution-free, residue-free, pollution-free measures for comprehensive control of Bradysia odoriphaga is currently a serious problem. The study on the occurrence regularity of Bradysia odoriphaga adult in Xuzhou, determined the relationship between temperature and developmental period indoor, systematic observation of adult emergence law and oviposition, determined the effect of soil environment on the larval development, high effect and low toxicity screening of single and mixture studies, Preliminary study on the effect of biomass charcoal influence on the occurrence and chemical control of Leek root maggot effect. The main findings and conclusions were as follows:Master the adult of Bradysia odoriphaga in Xuzhou annual occurrence. There were 5 peaks of population curve in a year, the overwintering generation feathered peak in late March and early April, generation larvae eclosion peak in early June, in late of July and early August, mid-September, between late October and early November. Spring adult is more concentrated, and the amount is greater than autumn, adults should serve as a year-round control focus of the spring.Bradysia odoriphaga shortened generation development period with the rise of temperature, at 15℃, 20℃, 25 ℃and 30℃. The longest development period of the whole generation was found at 15℃,which was 78.2 d. and the shortest was at 30℃, which was 23.4 days. Others at 20 d and 25 d were 32.0 d and 26.1 d respectively. The developmental zero of egg, larva, pupa of Bradysia odoriphaga was 4.2℃, 9.0 and ℃2.6℃. and the effective accumulative temperature was 90.4 d、295.1 d and 101.1 d, respectively. The lifespan and the amount of effective eggs laid per female were shortened with the temperature increasing. The longest life-spans were 11.9 d and 10.7 d for unmated female and male adult, respectively, and 7.6 d and 6.9 d for mated ones at 15℃, respectively. The amount of effective eggs was 109.4 per female. Under 30℃, the lifespan of unmated female and male ones were 2.6 d and 2.9 d, and mated female and male were 1.9 d and 2.7 d, respectively, the effective eggs laid per female was 49.4. The life table of Bradysia odoriphaga at test temperature was established. Deaths are concentrated in young larvae and pupa. The most favorable range of development temperature was 20 to 25℃ ℃.At 25 ℃, the adults eclosion peak appear on 5~10 d after emergence, the daily emergence was focused on 2:00~10:00, the female eclosion peak concentration in 4:00~10:00, the male has 2 eclosion peaks, at 2:00~8:00 and 18:00~24:00.The female could spawn 1~2 in life, lay large amount of eggs on the 2nd day, the daily oviposition peak occurred at 12:00~24:00. The effects of ratio of female to male on the amount of eggs laid per female and the longevity of the adults were no significant difference, the life-spans were 2d for female, and the male was 4d, the effective eggs laid per female was 80.Preliminary defined the relationship between soil environment such as soil type, temperature, humidity and soil organic matter content and larva development. The Soil temperature at 20℃~30℃, Soil water content at 20%~30%, organic manure content at 10%and better permeability could favour Bradysia odoriphaga occurrence and damage.Determination of a variety of high-efficient and low-toxicity insecticides to Bradysia odoriphaga toxicity, screened four single dose: imidacloprid, thiamethoxam, acetamiprid and diflubenzuron. The co-toxicity of single dose toxicity, the results showed that diflubenzuron with Imidacloprid or thiamethoxam in the ratio of 1:5 was the best. The best ratio of Imidacloprid or thiamethoxam with acetamiprid was 5:1.Rudimentary application of biomass carbon can reduce the number of adults of Bradysia odoriphaga and reduce the rate of damaged plants, there was no significant effect of chemical control.