Preliminary Study On The Influence Of Different Cultivation Methods On The Konjac Soft Rot Disease

Konjac is the herbaceous plant of Amorphophallus Areaceae. Since 80s of the 20^th century, the industry of konjac has developed very quickly, especially in the poor western areas of China, such as Sichuan Basin, Yungui Plateau, Wulin areas and Daba mountain areas where konjac has been the one of the most important characteristic cash crops .The soft rot disease(Erwinia carotovora (Jones) Holl. Pv. carotovora Dye) is the greatest threat to the production of konjac, and it is difficult to control and prevent the spread of pathogen only by using one pesticide. In this paper, several experiments were designed to reveal different agricultural techniques and pesticides on the control of soft rot disease. The result showed:1. Comparing to the incidence of the disease among 9 breeds of the elephant foot yam , and the konjac plants were grown in different altitude (800 m of Enshi city, 1200 m of Jianshi county and 600m of Xianfeng county), it showed that the incidence of breed "BM-1" was the lowest, reducing the incidence of the disease by 14.16% compared with the control.2. The effects of the seven different sowing times on the incidence of the disease were investigated. There were no significant difference among seven sowing times in case of uniform size and physiological ages of seed elephant foot yams. So the planting period was not the crucial factor affects the soft rot disease.3. The relationship between the incidence of the disease and the different amount of fertilizers were investigated, and the results showed that the incidence of the disease was significantly positively correlated with the amount of applied nitrogen fertilizers(R=0.92), but was negatively correlated with the amount of applied potassium and phosphorus fertilizers(R=-0.977 and -0.57, respectively).4. The relationship between different shading treatment and the incidence of soft rot disease was studied. The result suggested that it is a better way to plant corn along with the konjac.5. The effects of 10 different chemical pesticides treatments on the incidence soft rot disease were analyzed. It was showed that combining two or more germicides could reduce the incidence of the soft rot disease.6. The effects of different water content of the elephant foot yamkonjac on the incidence of soft rot disease were investigated. The results showed that the incidence of the soft rot disease was the lowest when the elephant foot yamkonjac consisted of 15 percentage of water.7. The influence of cultivated model such as intercrop on the incidence of soft disease was analyzed, the result demonstrated that soft rot disease significantly reduced when intercropping the elephant foot yam, Konjac with corn or the cash forest at an elevation of above 800m. On the other hand, the incidence of rot disease of konjac cultivating at the sunny slope would be higher than the shady slope below 800m.8. To analyze the effect of shady extent on the soft rot, different shading degrees by altering the density of corn and konjac were designed. It was showed that the incidence of soft rot disease was significantly decreased when the corn is about 1200-1500 per acreage and konjac is about 2500-3000 per acreage.