贡柑黑腐病发生规律研究

2011—2012年采用盆栽苗人工接种和田间调查相结合的方法,研究了贡柑产区近年为害严重的黑腐病(病原菌为Alternaria citri)的发生规律。结果表明:在人工接种条件下,其病原菌可以从没有伤口的叶面侵入,但更易从伤口入侵;贡柑和默科特桔最感病,其次是椪柑和南丰蜜桔,在有伤口和连续下雨的条件下马水桔、沙糖桔和温州蜜柑的嫩芽也偶被感染,橙类、柚类、柠檬和金柑抗病。在田间,贡柑、默科特桔最感病,其次是南丰蜜桔、椪柑,马水桔、沙糖桔、温州蜜柑未见发病。刚抽发的嫩梢和幼果易感病,组织越嫩越易感病,老叶、成熟果实感病少,幼树和刚结果树以及嫩梢多的树发病重。该病原菌孢子萌发需要高湿,下雨、高温、高湿有利于该病的发生和流行。夏梢发病最重,其次是春梢和幼果,秋梢发病轻。在人工接种条件下,只要下雨和温度达到15～30℃,1～3天即可显症,病斑沿着叶脉快速扩展。发病快、扩展快是其难防治的最大原因。

Study on Occurrence Regularity of Black Rot of Gonggan Citrus

The occurrence regularity of black rot of gonggan citrus was studied using artificial inoculation and field investigation methods in 2011—2012.The results showed that the pathogen could invade plant from the surface of healthy leaves without wound although it was easier for the pathogen to invade from the wound.By artificial inoculation,Gonggan and Murcott were the most susceptible cultivars followed by Ponkan and Nanfengmiju.The new buds of mashuiju,shatangju and satsuma mandarin were occasionally infected when there were wounds and continuous rain.Orange,pomelo,lemon and kumquat were resistant varieties.In the field,Gonggan and Murcott were the most susceptible varieties,followed by Nanfengmiju and Ponkan,and there was no infection on Mashuiju,shatangju and satsuma mandarin.Generally,young shoots and young fruits were susceptible,and mature leaves and mature fruits were less susceptible.Heavy infections occurred mostly on the young trees,fruiting trees and trees with a lot of young shoots.Spore germination requires high humidity,and therefore,rainy,high temperature and high humidity conditions facilitate the infection and spread of the disease.Summer shoots were the most severely infected,followed by spring shoots and young fruits.Autumn shoots were the least infected.Symptoms appeared within 1~3 days of infection by artificial inoculation of the spore under 15~30 ℃ and rainy conditions.The pathogen invaded rapidly along the veins,making it difficult to control the disease.