Effect of Furrow Mulching with P.E. Black Film and Dripping of Phosphorus Acid on Control of Phytophthora Root and Fruit Rot (Phytophthora capsici) Occurred in Field-grown Watermelon

摘要

The experiment was carried out to investigate the possibility in control of Phytophthora root and fruit rot (Phytophthora capsici) in field-grown watermelon during summer season. The disease started to occur in 29 June in the experiment field. To investigate which method was more effective against the disease, four methods, such as fungicide application, furrow mulching with P.E. black film, and dripping of phosphorus acid at root area and fruit setting area, were combined. They did not show any difference in the early stage. When harvest season was coming, the incidence was developed rapidly and reached to 100% and other treatments couldn't reduce the disease incidence very much, but furrow mulching with black film influenced the reduction of the disease significantly. Regression equations between the pathogen density and the diseased vine rate, the pathogen density and the diseased fruit rate, and the diseased plant rate and the diseased fruit rate were [diseased vine rate (%) = 40.17 + 5.07 × pathogen density (r =0.552 )], [diseased fruit rate (%) = 31.24 + 5.15 x pathogen density (r~2=0.566**)], and [diseased fruit (%) = -3.30 + 0.90 ×diseased vine rate (r =0.943 )], respectively. This result indicated that fruit infection would be influenced much more by infected vine rather than by pathogen density in soil.