渭北旱塬苹果黑星病的初侵染来源

 苹果黑星病是世界各苹果产区的重要病害之一,也是我国渭北旱塬苹果产区的新病害。近5年调查研究证明,渭北旱塬苹果落叶上分生孢子数量随时间推移呈急剧下降趋势,在春季苹果芽鳞萌动之前,分生孢子呈无色透明薄片状,均已失去存活力,芽鳞内外检测到分生孢子的数量很少,且均已丧失萌发力。果园中孢子捕捉结果表明,子囊孢子出现在先,分生孢子在后,两者出现时间相差15d以上,且捕捉到分生孢子的日期是在黑星病发病以后。对洛川县、白水县、长武县、永寿县、泾川县和平凉市等地苹果黑星病普查中未发现发病枝条,以菌丝体在枝条上越冬的可能性极小。综合以上试验结果,初步确定子囊孢子是渭北旱塬苹果黑星病的初侵来染,分生孢子不能越冬。

Inoculum of primary infection of Venturia inaequalis in arid plateau of Weibei,Shaanxi

Apple scab,caused by Venturia inaequalis(Cooke) Wint.,is regarded as one of the most serious diseases of apple all over the world.It is a new disease of apple on arid plateau of Weibei,Shaanxi province.The current investigation was conducted over a period of 5 years.Results showed that the number of conidia per square centimeter of apple scab lesion on fallen leaves was decreased greatly with time elapsing.The conidia in fallen leaves were colorless,transparent,with thin flake,and lost the viability before bud sprout.The average number of conidia in each bud collected from cultivars of Fuji and Gala in orchard on April 2nd 2003 was very few,but there were no viable conidia detected.The airborne ascospores and conidia of V.inaequalis were trapped with spore trapper and the results indicated that ascospores appeared before conidia.There were more than 15 days between ascospore and conidium appearance.At the same time,the date of conidia appearance was after that of symptom of apple scab.No diseased twigs were found in investigation of apple scab in Luochuan,Baishui,Changwu,Yongshou,Jingchuan,and Pingliang in arid plateau of Weibei.So,mycelium overwintered in twigs had very low probability.According to these results,the inoculum of primary infection of V.inaequalis is ascospore and conidia can not overwinter on arid plateau of Weibei.