Field Investigation Of The Onion Fly And The Effects On The Population Of Delia Antiqua In Different Humidity Conditions

Delia antiqua, is a worldwide agricultural pest belonging to the genus Deliathe, family Anthomyiidae of order Diptera, which is a destructive underground pests with wide distribution. They mainly do harm to the liliaceous plants by drilling into the plant root. Then, the root will be cankered and the leaves gradually turn yellow and wilting. As the result, it will cause a great deal of damage to production of allium crops. In recent years, onion fly is in the increasingly fierce trend of occurrence of allium crops, caused massive death in crop production and serious economic losses. So the investigation and research on it will be imperative. This study is mainly combining by outdoor investigation and laboratory research, exploring the effect of environmental humidity on the onion maggot biological characteristics and population.Through the systematic field investigation we found that early and mid June and late September is the flourishing period of Delia antique in Yangling, a large number of pupa appeared in early October and late July, the reason for this phenomenon is high summer temperature, we should take steps before late May and mid September. After the precipitation, the high soil humidity lead to the larval stage shorten and some larvae into pupa stage. The experiment results shows that the most suitable relative humidity for the population of onion flies is RH 40%-50%.Too low relative humidity(RH 30%) made the incubation period and developmental duration longer, the mortality of larvae increased and the life of adult Delia antique shorten. And high relative humidity(RH 70%) could make brooding time,incubation period and developmental duration shorter,it also shorten the life of adult Delia antique. Under favorable humidity(RH 50%), the intrinsic rate of increase of Delia antique population is 0.097 d-1, the net reproduction rate of Delia antique population is 113.79 offspring per individual, the finite rate of increase of Delia antique population is 1.10d-1, the mean generation time of Delia antique population is48.63 d.