STUDIES ON THE BIONOMICS AND CONTROL METHODS OF THE SAWFLY HEMICHROA CROCEA(GEOFFROY)

The sawfly,Hemichroa crocea (Geoffrey) is a new forest insect pest in China.It severely defoliates the alder Alnus cremastogyne Burk in Sichuan Province.There are two generations per year in Wusheng County.Full-grown larvae drop to the ground.Here they spin cocoons in the top 3~5 cm of soil and aestivate or overwinter as prepupae.The adults of the second generation emerge in the following mid-March when the temperature is above 12℃ and the larvae appear during late March.The adults of the first generation emerge in late October when the temperature is at about 15℃.The larvae of the second generation appear during early November and mature in late November.The use of 80% Dichlorvos at a dilution of 1:2000,or 25% Sha-Chong-Shuang of 1=800,or 40% Omethoate of 1:1500,or 40% ZML Fenvalerate of 1:12000 in controlling the first to third instar larvae reached very high mortality.Besides,digging up the soil in which the pest aestivate or overwinter could destroy the prepupae and the pupae.