멜론 흰가루병의 피해해석 및 경제적 방제수준 설정 = Economic Threshold and Yield Loss Assessment due to Powdery Mildew Caused by Sphaerotheca fusca, in Melon

다국어 초록 (Multilingual Abstract)

This study was carried out to develop the economic threshold for powdery mildew in melon, at Gimje and Iksan of Jeonbuk province. To establish the relationship between degree of incidence of powdery mildew with yield and sugar content in the spring and the fall cultivation season, seven levels of disease incidence were maintained, at the melon cultivation experimental sites. In the spring cultivation season, the degree of infected leaf area was controlled under 5, 10, 20, 30, 50, 70, over 70% by spraying fungicide, and under 5, 6~10, 11~ 15, 16~20, 21~30, over 30% of infected leaf area without any spray of fungicide, in the fall cultivation season. Powdery mildew was diagnosed as Sphaerotheca fusca. Powdery mildew caused decrease in fruit weight, fruit length and sugar content. This decrement increased with the increase in degree of incidence of the disease. In the spring cultivation season, fruit wt. decreased by 248g, length 1.5cm and sugar content by 0.68brix, due to 30.60% increase in incidence of disease while in the fall cultivation season, fruit wt. decreased by 34g and sugar content 0.55brix, due to 12.44% increase in disease incidence. The incidence of powdery mildew was increased from 0.9% in early time to 60.8% in the spring and from 24.8 to 75.3% in the fall cultivation season at non-sprayed site. In the spring season, wt. ＆ sugar content of melon fruit was not affected at the incidence level under 10% and 30%, respectively. In the fall season, at under 20% level of incidence, fruit sugar content was remain unaffected. Disease intensity exhibited negative and significant correlation with the fruit weight and sugar content. The adverse effects of the disease on these characteristics resulted to low yield, exhibiting significant negative correlation with disease intensity. There existed a close correlation between percentage of infected leaf area with yield and sugar content, grown in the poly-house (spring: r=-0.86, r=-0.73, fall : r=-0.64, r=-0.87 ). The economic injury level for powdery mildew was 13.3% according to Y=4.8X＋64.88, R2=0.74, r=0.86 and the economic threshold of powdery mildew at level 80% was below 10.6%.