| Curculio davidi Fairmaire belongs to Coleoptera family Curculionidae genus,and is one of the most harmful pests to the fruits of Castanea and always rampant in the principal areas for chestnuts producing of China.It has a long history to cultivate chestnut in Dechang County,which possesses cultivars in good quality and large quantity,becoming the vital local industry and also a method to help native habitants out of poverty.The damages from Curculio davidi becomes severe over the past years and threatens the chestnut industry,however,it is difficult to predict and prevent losses resulted from Curculio davidi due to the lack of relevant materials.Thus carrying out the studies of Curculio davidi becomes quite critical on its biological features,regulation of occurrence and pollution-free control methods,which will guarantee the steady productivity of chestnut and development of this industry,improving the eco-development of rural areas to meet the demand of anti-poverty.This study observed and tested the biological features and regulation of its behavior,and explored three pollution-free control methods.The main results are as follows:1).The adult individuals emerged from late May to late June(30 days in all)in 1250 to 1350 m.The amount of unearthed Curculio davidi varied day to day and the maximum period was from late May to early June with the sexual ratio of 1:1.The pace of unearthed Curculio davidi showed a trend of descent with slowing down in early June and leveling off in late June.Both the amount and pace of unearthing was greatly influenced by weather,and rainy days gave Curculio davidi advantages to come out the ground.The phenology of chestnut was closely related to the emerging of adults,possessing a territory feature as well.The filling stage of cupule was also the stage for nutrition uptake,courtship and oviposition,which should be highly attached as it was the critical stage for controlling Curculio davidi.2).The adults flew to the chestnut trees after unearthing and began to eat male inflorescence,shoot,petiole,damaged tissue,cupule and seed in late filling stage of chestnut.There were no significant courtship features.When getting involved,the adults exhibited an attempting courtship with face-to-back copulation lasting tree to six hours.The oviposition location was often chosen to the cupule and bottom of seed(usually on the cotyledon surface),and the oviposition aperture would disappear with the growth of seed but not with cupule.The amount of eggs were usually from one to eight in seed and the incubation duration was six to eight days.The female individuals were more likely to lay eggs in cupule with thin skin and short,few and soft prickles.In addition,they chose chestnut from precocious one to medium mature one,then to serotinous one from time to time.3).There was no significant taxis reaction in both male and female adults and the rate of taxis to the opposite sex was 35.56% in both individuals,suggesting that there was no significant volatile sex pheromone between male and female adults.The taxis test to food showed the concentration of honey has no significant impact on Curculio davidi,maintaining a rate of 40-55%.The taxis test to light manifested the Curculio davidi adults were most sensitive to reflective black and purple light with a percentage of 56.11 and 55.00 respectively.4).Honey water with 30% concentration induced 3.4 adults each day,showing no significant effect.The reflecting black and purple light induced 2.3 and 1.9 adults per day respectively.Honey induction and light induction were greatly influenced by weather and other factors,needing further exploration.However,after being put into soil for 30 days,Beauveria tenella had a pretty significant control that 76.67% of underground mature larvae of Curculio davidi was infected and killed. |
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