柠檬红锈藻病为害与药剂防治

Occurrence and Chemical Control of Red Rust Alga in Lemon

柠檬红锈藻病（CephaleurosparasicasKarst）是造成柠檬树未老先衰，柠檬减产的一种枝干病害，在云南省柠檬产区发生普遍，且为害较重。通过不同龄期柠檬植株和枝干对红锈藻病的抗病性调查，结果表明：红锈藻病在柠檬植株定植2～5年发病，以定植3～4年发病最重，发病率均为100％，病情指数分别为72．20％和84．27％；柠檬枝干2～5年生均发病，发病率为100％，以2、3年生枝干病情指数最高，分别为82．56％和87．68％；定植1年植株和1年生枝干均不发病。9种杀菌剂的大田筛选试验表明：75％百菌清和46％氢氧化铜的防治效果较好，施药后2d的防效分别为56．79％和48．47％，施药后5d的防效分别为100％和75．19％。但46％氢氧化铜等铜制剂与其他杀菌剂、杀虫剂混合使用时易造成柠檬幼果药害。

Lemon red rust alga caused by Cephaleuros parasicas Karst is a widespread and serious disease of lemon branches in Dehong , Yunnan province , and it results in the premature senility of lemon tree and the decrease in lemon yield .The resistances of lemon plants and branches at different ages to red rust alga were investigated .It was found that red rust alga occurred in the lemon plants which have been planted for 25 years.Its occurrence in 3-year-old and 4-year-old plants was more serious with the incidence of 100%, and their disease indexes were 72.20%and 84.27%respectively.The 25-year-old lemon branches were infected by this alga with the incidence of 100%, and the disease indexes of 2 -year -old and 3 -year -old branches were 82.56%and 87.68%respectively.Red rust alga was not found in one -year-old plants and one-year-old branches.The field tests for the screening of 9 kinds of fungicides showed that 75%Chlorothalonil and 46%Copper hydroxide had better control effects against this alga, and their control effects were respectively 56.79%and 48.47%2 days after spraying, and 100%and 75.19%5 days after the application .However, the mixed application of 46% Copper hydroxide with other fungicides or pesticides easily caused phytotoxicity to the young fruits of lemon .