Control Effects of 9 Fungicides on Citrus Canker

HUANG Ze-pei, ZHOU Ya-lin, LONG Jian-guo, MO Jun-ping, SUN Wei-si

1. Plant Protection and Inspection Station of Agricultural and Rural Bureau of Mayang County, Mayang 419400, PRC;

2. Agricultural Technology Extension Station of Agricultural and Rural Bureau of Mayang Miao, Mayang 419400, PRC

Abstract In order to screen out effective fungicides for controlling citrus canker,the control effects of 9 fungicides on Jinhong bingtang orange canker were studied.The results showed that 77% cupric calcium sulfate WP, 30% copper oxychloride SC, 46% copper hydroxide WG, 30% thiodiazole-copper SC and 40% zinc thiazole SC had better comprehensive control effect on citrus canker, 6% benziothiazolinone WG had an average effect, 3% zhongshengmycin AS, 2% kasugamycin AS and 33.5% oxine-copper SC had poor control effect. Therefore, fungicides could be used alternately or choose compounded preparation. In addition, adjuvants could be considered in use, which was an effective way to enhance efficacy, reduced dosage and delayed pesticide resistance.

Key words Citrus canker; Copper preparation; Biological agents; Thiazoles;Heterocyclic; Control effect; Efficacy test

1. Introduction

Citrus canker is a bacterial disease caused by

Xanthomnoas axonpoodis

pv.

citri

, which is mainly distributed in Yunnan, Guangxi,Jiangxi, Hunan and other citrus planting areas in China. The disease mainly damages the new leaves, branches and young fruits of citrus,and affects the growth of citrus trees (especially young trees). When the damage is serious, it will cause a large area of fallen leaves, dead branches and fruit drop of citrus trees, which not only has a huge impact on the yield of citrus, but also seriously affects the quality of fruit. Usually, the pathogen can survive for several months under dry conditions. Therefore, after citrus picking, the pathogen can live in the diseased branches and leaves, especially in the autumn shoots. After next spring, the pathogen will overflow from the diseased spots on the host branches and leaves and spread through insect vectors, natural wind and rain and some agricultural operations. At the same time, it can also spread through seedlings, cuttings and scions.

Mayang Miao Autonomous County is an important production area of Bingtang orange in Hunan and even the whole country, enjoying the reputation of "the hometown of Bingtang orange in China"; Bingtang orange has become a major pillar industry in Mayang. In recent years, the occurrence and prevalence of citrus canker disease in Mayang orange were increasing. At present, copper preparations are mainly used to control the disease,combined with daily agricultural management,which has a certain control effect, but still cannot stop the occurrence of citrus canker in successive years.In addition, the continuous and large-scale use of copper preparations has certain risks to environmental pollution. In this study, 9 kinds of fungicides were selected to carry out the field control effect test, and some good fungicides were selected to provide the basis for the control of citrus canker.

2. Materials and Methods

2.1. Test site

The experimental orchard was located in the citrus base of Sannong Brothers Forestry Development Co., Ltd., Lanli Town, Mayang County. The orchard was windward sloping paddy field with red and yellow sandy soil, and canker disease has occurred over the years. The cultivar was Jinhong Bingtang orange, which was 9 years old and grew well. The management of fertilizer and water was consistent with that of surrounding citrus orchards.

2.2. Test reagent

There were 10 treatments in the experiment.Treatment 1, 77% cupric calcium sulfate WP 500 times(Adama Beijing Agricultural Technology Co., Ltd.);treatment 2, 46% copper hydroxide WG 1 500 times solution (DuPont company, USA); treatment 3, 300 times solution of 30% copper oxychloride SC (Hunan Shengyu Co., Ltd.); treatment 4, 33.5% oxine-copper SC 800 times solution (Zhejiang Haizheng Chemical Co., Ltd.); treatment 5, 30% thiodiazole-copper SC 400 times solution (Zhejiang Longwan chemical Co.,Ltd.); treatment 6, 3% zhongshengmycin AS 500 times solution (Fujian Kaili Biological Products Co., Ltd.);treatment 7, 2% kasugamycin AS 300 times solution(Shandong Rushan Hanwei Biotechnology Co., Ltd.);treatment 8, 6% benziothiazolinone WG 100 times solution (Adama Beijing Agricultural Technology Co.,Ltd.); treatment 9, 40% zinc thiazole SC 750 times solution (Zhejiang Xinnong Chemical Co., Ltd.);treatment 10, water control. There were 2 orange trees in each treatment plot, which were repeated for 3 times and random block arrangement, isolation zone between plots. The 9 chemical treatments and the control were all added with metriam WG (BASF China Co., Ltd.) and leaf fertilizer Meizuo (organic matter≥110 g/L, Zn+B 21～30 g/L (Valragro S.A.,Italy). Among them, 22% Thiamethoxam & Lambdacyhalothrin SC (Syngenta Nantong Crop Protection Co., Ltd.) and 45% Hydrazine & Pyridaben SC(Shaanxi Welch Crop Protection Co., Ltd.) were added in the first application.

2.3. Application method

The test was applied 3 times, the first time was on April 27, 2020, the second was on May 15, and the third was on June 3, all were sprayed by crown spray method.

2.4. Investigation method

15 d after the third application (June 17), the canker disease investigation was carried out at fixed points. Each tree was sampled from five directions:East, South, West, North and middle. All leaves on 10 fruits and 2 new shoots were investigated at each point. The number of leaves and fruits at all levels were recorded, and the disease index and control effect were calculated.

Classification criteria refer to field efficacy test criteria for citrus canker: grade 0, no lesion; grade 1, 1～5 lesions per leaf (fruit); grade 3, 6～10 lesions per leaf (fruit); grade 5, 11-15 lesions per leaf (fruit);grade 7, 16～20 lesions per leaf (fruit); grade 9, more than 21 lesions per leaf (fruit).

The formula of control efficacy was as follows:

Incidence rate (%)=sick leaf (fruit)/total leaf number (fruit)×100%

Disease index=〔∑(number of diseased leaves(fruits) at all levels×relative value)/(number of investigated total leaves (fruits)×9)〕×100

Relative control effect (%)=(disease index of control area-situation index of treatment area)/situation index of control area×100

3. Results and Analysis

3.1. Safety evaluation

In the whole process of the experiment, after the application of 9 kinds of chemicals, the growth of citrus fruits and leaves was normal, the sprouting of new shoots was normal, and there was no phytotoxicity reaction; and there was no obvious effect on other non-target organisms and other diseases and insect pests; it indicated that the tested chemicals were safe for the growth of citrus in the dose range.

3.2. Control effects on citrus leaf canker

The control effects of 9 pesticides on citrus leaf canker were shown in Table 1. The control effects of 77% cupric calcium sulfate WP 500 times solution,30% thiodiazole-copper SC 400 times solution, 30%copper oxychloride SC 300 times solution and 46%copper hydroxide WG 1500 times solution were better, and the relative control effects were 93.82%,91.45%, 86.12% and 85.99% respectively; the control effect of 40% zinc thiazole SC 750 times solution was average, and the relative control effect was 79.19%;the control effects of 3% zhongshengmycin AS 500 times solution, 2% kasugamycin AS 300 times solution, 33.5% oxine-copper SC 800 times solution and 6% benziothiazolinone WG 1000 times solution were poor, and the relative control effects were 44.46%, 56.59%, 59.81% and 67.01% respectively.The incidence and disease index of young fruits treated with the 9 fungicides were the lowest in the 77% cupric calcium sulfate sulfate WP 500 times solution, only 6.12 % and 0.831; 2% kasugamycin AS 300 times treatment was the highest, up to 21.69% and 5.842; the incidence rate of control was 57.22%, and the disease index was 13.459.

Table 1 Control effects of 9 pesticides on citrus leaf canker

3.3. Control effects on citrus fruit canker

The results showed that the control effects of the 9 pesticides on citrus fruit canker were shown in Table 2. The control effects of 300 times solution of 30% copper oxychloride SC and 750 times solution of 40% zinc thiazole SC were very good, and the relative control effects were 96.77% and 92.83%respectively; the control effects of 30% thiodiazolecopper SC 400 times solution, 77% cupric calcium sulfate WP 500 times solution, 46% copper hydroxide WG 1500 times solution and 6% benziothiazolinone WG 1000 times solution were 89.60%, 87.76%,85.66% and 83.48% respectively; 2% kasugamycin AS 300 times solution, 33.5% oxine-copper SC 800 times solution and 3% zhongshengmycin AS 500 times solution had poor control effect, and the relative control effect was 60.32%, 62.00% and 76.34%respectively. The incidence of young fruits treated with 9 fungicides was the highest in the 300 times solution of 2% kasugamycin AS, reaching 21.03%; the second was achieved by using 46% copper hydroxide WG 1500 times solution and 33.5% oxine-copper SC800 times solution, both of which are 10.67%; 30%the incidence rate of young fruit treated by copper oxychloride SC 300 times was lowest, only 3%. The incidence rate of control was significantly higher than that of the 9 treatments, up to 35%. The disease index of the 9 treatments was the highest in the 300 times solution of 2% kasugamycin AS, reaching 4.100,followed by the 800 times solution of 33.5 % oxinecopper SC, reaching 3.926; the third was treated with 3% zhongshengmycin AS 500 times solution,which reached 2.444; the disease index of the control treatment was as high as 10.333.

Table 2 Control effects of 9 fungicides on citrus young fruit canker

4. Summary and Discussion

At present, chemical control is the main method to control citrus canker. The results showed that 9 fungicides had certain control effects on citrus leaf canker. Among them, 3% zhongshengmycin AS 500 times solution, 2% kasugamycin AS 300 times solution, 33.5% oxine-copper SC 800 times solution and 6% benziothiazolinone WG 1 000 times solution had poor control effects on citrus leaf canker; 77%cupric calcium sulfate WP 500 times solution, 30%thiodiazole-copper SC 400 times solution, 30% copper oxychloride SC 300 times solution and 46% copper hydroxide WG 1 500 times solution had good control effect on citrus leaf canker. 3% zhongshengmycin AS 500 times solution, 2% kasugamycin AS 300 times solution, 33.5% oxine-copper SC 800 times solution had poor control effect on citrus fruit canker, 30%copper oxychloride SC 300 times solution, 40% zinc thiazole SC 750 times solution had good control effect on citrus fruit canker, 30% thiodiazole-copper SC 400 times solution, 77% ccupric calcium sulfate WP 500 times solution, 46% copper hydroxide WG 1 500 times solution, 6% benziothiazolinone WG 1 000 times solution had better control effect on citrus fruit canker.

Comprehensive analysis showed that 77% cupric calcium sulfate WP 500 times solution, 30% copper oxychloride SC 300 times solution, 46% copper hydroxide WG 1 500 times solution, 30% thiodiazolecopper SC 400 times solution, 40% zinc thiazole SC 750 times solution had better comprehensive control effect on citrus canker. In the production and application, it can be used in turn or in combination.In addition, additives can be considered in the use of drugs, which is also an effective way to strengthen the efficacy, reduce the dosage and delay the emergence of drug resistance.

At the same time, the control requirements of new and old citrus orchards were different. In order to control citrus canker in "new orchard", strict quarantine, establishment of disease-free nursery,seedling treatment, strengthening management and other measures can be taken to build disease-free area, supplemented by other agricultural management measures and chemical control. It is suggested that comprehensive prevention and control measures should be taken for the old orchard with persistent occurrence of citrus canker: first, clean the orchard in winter, dispose and destroy the residual value of canker pathogen infection, dead leaves and fallen fruits in a centralized way, and spray disinfectant to kill the residual pathogens on trees and soil, so as to reduce the number of pathogens; second, strengthen the control of citrus leaf miner. Timely control of citrus leaf miner can reduce the occurrence of citrus canker; the third is to strengthen the management of water and fertilizer, supplemented by reasonable wiping summer shoots, cultivating spring and autumn shoots, effectively reducing the occurrence of citrus canker; the fourth is to take timely chemical control,with each interval of 15 d. The tree crown spraying method is used for spraying. In the early stage, the shoots are mainly preserved, and in the late stage, the protection of young fruits is the most important part,with spraying chemicals for 3～4 times.