Study On Occurrence And Control Countermeasures Of Harmful Organisms With Rapeseed In Huangzhong County Of Qinghai

Huangzhong County is an agricultural county in Qinghai Province.The three largest crops in this county are wheat,rapeseed and potato,amongst there is the largest planting area for rapeseed.In the process of crop production and management,the controlling of harmful organisms will directly affect the yield,quality of the crops and the benefits for farmers.In order to better forecast crop harmful organisms and to provide theoretical basis for high efficient control,an all-round and systematic large-scale investigation on rapeseed harmful organisms was conducted in Huangzhong County.In this study,the species,biological features and occurrences of harmful organisms with rapeseed were investigated in Huangzhong County.The ways that harmful organisms take to affect the rapeseed were analyzed,and the efficient and comprehensive controlling countermeasures were put forward,especially some green technologies to control Phyllotreta spp,Ceuthorrhynchus asper and Meligethes aeneus.The main results obtained are listed as follows:1)There were 37 rapeseed pests in Huangzhong County,including 2 diseases,6 insect pests and 29 farmland weeds.The diseases included Sclerotinia scolerotiorum and Peronospora parasitica.The pests included Phyllotreta spp,Ceuthorrhynchus asper,Meligethes aeneus,Plutella xylostella,Evergestis extimalis and Aphidoidea.The weeds mainly included Elsholtzia densa,Chenopodium album,Brassica campestris,Hypecoum leptocarpum,Sonchus arvensis,etc.2)The symptoms,habitats and occurrence rules of rapeseed diseases,the identifying characteristics,damage characteristics and occurrence rules of insect pests,and the types and quantity of weeds were further clarified in Huangzhong County.Sclerotiniasclerotiorum occurred in late July to early August.Phyllotreta spp and Ceuthorrhynchus asper occurred from early May to late June.Meligethes aeneus and Plutella xylostella occurred from early June to late July.Plutella xylostella and Evergestis extimalis occurred from late July to early September.The aphidoccurred mainly from early July to late August.Weeds causing serious damage in wet areas along the river mainly included Poa annua,Mentha haplocalyx,Polygonum aviculare,etc.In the lower hilly areas,Herba Taraxaci,Hypecoum leptocarpum,Sonchus arvensis were the most harmful species,while in the hilly areas Brassica campestris,Elsholtzia densa,Chenopodium album were the most harmful species.Combined with meteorological information,the forecasting information would be released 10 ~ 15 days before the occurrence of crop diseases and insect pests,which can guide the large-scale control.3)Comprehensive control measures and green control techniques of rapeseed pests were further clarified in Huangzhong County.Based on agricultural,biological,physical and chemical control measures,comprehensive control measures mainly included pesticide seed dressing,soil treatment,thinning and weeding,pest control and field weed control.Green control technologies included color plate trapping,sex attractant trapping,insecticidal lamp trapping,biological pesticide prevention and control,etc.4)The control techniques of rapeseed flea beetle,stem weevil and sap beetle were optimized and put forward,including the utilization of carbosulfan and other conventional pesticides,pesticide additives and yellow-blue plate.At the early stage of rapeseed emergence,seed dressing with 40% carbosulfan emulsifiable concentrate 300 mL/ha had a significant effect on controlling rapeseed flea beetle,with a damage index of 20%.In the 15 d post-seedling investigation,seed dressing with 40% carbosulfan emulsifiable concentrate 150 mL/ha was the best to control stem weevil of rapeseed seedling,with the damage rate of 15%.From the viewpoint of population decline and control effect,the pesticide adjuvant Qigong led to greater population decline rate and control effect on rapeseed pests with other pesticides.After adding Qigong into Jiqi chemicals,the control effects on striped flea beetle,blue flea beetle,stem weevil and sap beetle were increased by 18.52%,5.57%,0.75% and 8.00% respectively.After adding Qigong into beta-cypermethrin,the control effects on yellow striped flea beetle,blue striped flea beetle,stem weevil beetle and sap beetle were increased by 11.11%,32.77%,46.38% and 9.34%,respectively,which shows that the control effect of pesticides was largely improved by the adjuvant.The blue plate had better trapping effect on sap beetle,while the fully degradable yellow plate had better trapping effect than the common yellow plate,and was easier to degrade after being deeply buried.