Studies On Research And Control Weed In The Tobacco Field In Yunnan

An investigation of weeds classification and the group distribution in the tobacco field had been made in Yunnan province, and the growth and decline regularity of weeds, the impact and harm on tobacco, and the relationship between weeds and tobacco disease and insect pests were researched, and 14 kinds of herbicide and black mulch film were to be done the screening test of preventing and killing off weeds, a harm test of herbicide was made. The main research results were as fellows:1. The group had been collected and ordered more than 1 000 pieces of photos of weeds, identified the main 30 families and 138 varieties of weeds in tobacco fields in Yunnan province.2. The growth and decline regularity of weeds has been clarified as: with sufficient moisture, the germinating of weeds has close relationship with field moisture and rainfall; without abundant rainfall and artificial irrigation after tobacco transplant, the weeds has no condition of germinating.3. The impact and harm of weeds on tobacco is: without preventing and killing off of weeds during the entire field crop growing period, without artificial weeding after covering or uncovering the mulch film, the fresh weight of weeds may reach over 300 times of that of artificial weeding, the weeds may result in tobacco plant height 2.3～2.4 cm shorter than that of normal weeding, the tobacco leaf surface area factor reducing 0.16～0.19, tobacco leaf output dropping by about 25% and economic benefits dropping about 28%. Tobacco leaf yield per mu (Y1), value per 666.7 m~2(Y2) and fresh weight of weeds has an obvious negative relationship(Y1=153.3158-0.0103X; Y2=1464.0642-0.1313X) .4. The relationship between weeds and tobacco disease and insect pests is: the incidence of anthracnose, brown spot, green peach aphid, tobacco budworm and cotton leafworm has close relationship with quantity of weeds in tobacco field, the more luxuriantly the weeds grow, the more seriously tobacco disease and insect pests occur.5. The preventing and controlling method were to put forward , which were that uncovering mulch film and soil dressing + using herbicide after of weeds burgeoning + furrow weeding"for the first time, which was in conformity with the characteristics of Yunnan tobacco planting.