Study On The Control Of Spodoptera Exigua (H(?)bner) In The Bunching Onion Field In Chongqing

Beet armyworm, Spodoptera exigua (Hubner), which originated in Southeast Asia, is a widely distributed polyphagous pest of numerous host plants, including 28 species of crops and 32 species of vegetables which sustain heavy damage. Now some domestic researches have reported the beet armyworm's damage on the shallot and its elementary management by insecticides. In this research, further study was conducted in shallot field to explore some crucial life habit, economic threshold and comprehensive management methods. Results are as follows:1. Life habit of beet armyworm in the bunching onion field.Among kinds of shallots in Chongqing, beet armyworms mainly damage bunching onion {Allium fistulosum L.var.caespitosum Makino) , which is planted from March to April and propagates two or three times by division of the bush until September. The output ranges from 2500 to 3000kg per 667 m2. Insecticide is sprayed 2.5 times averagely during each growing period, depending on the occurrence of the larvae in the field.The larvae climb up along the tubular leaf after egg hatch and gather in shade feeding. 3~4 days after hatched, larvae spread around and feed alone. Phenomenon of drilling the leaf occurs during this period. Old larvae hide in culm cluster or soil nearby for pupation. Female adults always select healthy and strong leaf to lay eggs on.2. Forecast of beet armyworm development in the field.Occurrence of larvae in the field is forecast roughly by Insect Pest Forecasting Lamp. The predicated result merely based on the lamp's information is qualitative. Four bands of oval's development were listed after oval dissection experiment on beet armyworm. Meanwhile, the rule of the eggs number changing with the days is also found. Analysis showed the number of eggs laid on...