Courtship Behavior And Sex Pheromone Of Chinese Chive Fly, Bradysia Odoriphaga (Diptera:Sciaridae)

The Chinese chive fly, Bradysia odoriphaga Yang & Zhang (Diptera:Sciaridae), is a most serious pest of Chinese chive, Allium tuberosum Rottle ex Spreng (Liliaceae). The larvae of B. odoriphaga feed on the roots and stems, that causing plants to die. Less use of insecticidal treatments, the fly can cause more than 50% yield loss in Chinese chive and may be sometimes even destroy the entire production. Chemical insecticides (e.g., organophosphates, carbamates,) is the most prevalent management practice against B. odoriphaga larva in China now. However, the pest remains very difficult and low efficient to be controlled because the larvae live in the soil, hardly contact with applied insecticides. Therefore, we proposed that we may find a way through study on its courtship behavior and sex pheromone to control adults which are in air as an alternative to application of insecticide into soil. Here are the results:1) The population dynamic of Chinese chive fly in greenhouse in BeijingAfter screening the methods to survey and monitoring populations in field, a field survey on the population dynamics of B. odoriphaga in greenhouse Chinese chive ecosystem was conducted in Shunyi district, Beijing, China during March,2013 to March,2014. The results showed that there were 2 peaks of larval population in early May and late June, respectively. For adult’s population, there were 3 peaks in the end of April, the end of May with highest population and the late June, respectively. From mid July to late August, both of adult and larvae could not be observed in the field. Our data showed that damage rate of chive plants exceeded 80% after late April. This survey provides a basis for control of B. odoriphaga in greenhouse Chinese chive field in Beijing. Furthermore, the results of the effects of temperature on mortality and sex ratio of the fly showed that higher temperature, over 35℃, most flies dead and this may be one of the reasons which cause populations in greenhouse field very low during summer. This result can provide the basic information for field monitoring and controlling of the pest.2) Courtship and mating behavior of B. odoriphagaTo develop behavioral control method for adults of the pest, the observations on its courtship and mating behavioral activities were conducted under laboratory conditions. Virgin male flies performed obviously courtship which includes orienting, wings extending and vibrating, chasing, and curling abdomen before mating. However, female flies performed orienting, wings extending and up-down abdomen. Further, male flies performed chasing and mating more at night, and wing vibration more during the day. A comparison experiment results showed that wing vibration, chasing, and tail curling are specific behaviors used in male courtship. Courtship and mating mostly occurred within 3 days after emergence, and male courtship and mating activities declined significantly with age. The extracts of female body tails attracted male flies, in contrast, the extracts of male body tails did not attract females. Our results suggest that B. odoriphaga male performs obvious courtship behavior which may be evoked by the sex pheromone released by female flies. Our results may improve the program of integrated management of the pest by development of the use of sex pheromones in mating disruptions or trap-and-kill methods, to alternate the opposed one to employing insecticides in the soil to control larvae based on the understanding of the fly’s courtship and mating behaviors.3) Identification of sex pheromone and field applicationVolatile compounds were collected by solid phase micro extraction (SPME) and headspace method from live B. odoriphaga males and females respectively and analyzed by gas chromatographic mass spectrometer (GC-MS). There are six compounds are female specific and were used in behavioral experiments to examine their functions. Only three were of the compounds attractive to males in a T-maze bioassay in laboratory. And the results of the experiment with a series of proportions of these three compounds mixture showed that at one proportion mixture blend was most attractive to males and in different distances from 10cm to 50cm. Three types of trap were designed according to the previous experiments results, and a field experiment was conducted in greanhouse in Beijing from March to April. Only yellow sticky card with attractant at concentration of are most effective to attract males. And these results showed quite useful for monitoring and controlling of the pest in agricultural systems.