Studies On The Bionomics Of Lissorhortrus Oryzophilus Kusche And It's Control Methods

Rice water weevil Lissorhortrus oryzophilus Kusche is one of the disastrous pests in rice production as well as a key object of plant quarantine.The rice water weevil were found occasionally in several counties in Hanzhong City,a main rice production area in southern part of Shaanxi Province,in recent years.Biology and bionomics of the rice water weevil as well as its effective control methods were systematically investigated and studied in order to provide scientific and practical support in this paper.1.From 2006 to 2007,with the assistance of the staff from local Plant Protection Department in Hanzhong City,we did systematically investigation on rice water weevil,and finally fully comprehended its distribution in Hanzhong.The epidemic regions covered 10 counties,80 towns,719 villages and 4486 brigades,including Liuba,Mianxian,Chenggu, Xixiang,Zhenba,Ningqiang,Yangxian,Nanzheng,Lueyang and Hantai.This pest took place at both seedling bed and transplant field,the total infested area amounted to 18 061 mu and 180 780mu respectively.2.Through observation in the field,the biological behavior and regularity of outbreak of rice water weevile in Hanzhong rice production region were preliminarily understood.The pest took place from March to September,and its group migration reached the peak in the last ten-day of April,and from the end of May to the middle of June respectively.After migrated to rice field from seedling bed,the pest continued to exert damage to plants.The female adults started to oviposit in seedling fields during the first 20 days of May,entering ovipostion climax in late June and lasting to early July.The larvae began to hatch in early June.From mid-June to early July,the larvae reached the peak,and decreased greatly from mid August to late August.From late June to early July,fully grown larvae began to pupate,reaching climax in early and mid July. The number of pupae would reduce largely during the first twenty days of September.The F1 adults appeared in early July.From late June to early August,rice water weevil reachd its eclosion summit.According to these results,the favorable periods for the pest management should not be missed in order to prevent outbreak of rice water weevil.3.Investigation on the rest time and niche on rice seedlings,field distribution pattern and overwintering site of rice water weevil were carried out.It is found the distribution pattern of rice water weevil showing a combination of individually surviving and taking place in patches, and they always infested assembly.The pest mainly fed on the middle and lower parts of rice stalk,usually taking place in the morning and evening,showing photophobia to some extend. Generally,the nearer the rice fields to the river,the more serious the damage would be caused by rice water weevil.It is also found that the rice water weevil overwintered mainly close to banks of water ways.The pest overwintered underground at epidermal layer 0-5 cm,and could transfer from ridges to ditchs in early autumn,and finish transfering in November.4.Due to an extreme diversity of pesticides for control on rice water weevil in the market, especially because of their various effects,among them several kinds pesticides,which were used most commonly on rice water weevil management in recent years,were chose for field experiments.The results showed that the following agro-chemicals had relatively high effect to control rice water weevil,3%Andean music benzene granules 1kg/mu,10%Phorate phoxim 1 kg/mu.5%of Regent(80ml/mu spraying) has good effect on the larvae.The following reagents are effective on the adult,5%of Regent 60ml/mu,36.8%of water-amine(Victoria Rice) EC Weidao 60 ml/mu and 20 percent digoxin·triazolam EC Phoxim triazophos 75ml/ mu.Thus we could come to the conclusion that these reagents can be recommended and promoted to control rice water weevil.5.In Mianxian county,Hanzhong City,introducing and popularizing base was established in the area,where the loss caused by rice water weevil was very serious,and the base area extended to about 25 000 mu during a 3-year period.In demonstration base,the loss rates caused by diseases and pests were below 8%,and 78%less than in control area.Additionally, the average yields increased by 12.85%.These results applied that the demonstration base had made significant economic,social and ecological benefits.