Evaluation of the Effects of High-efficiency Compound Formulations on the Prevention and Control of Sugarcane Brown Rust

Wenfeng LI Rongyue ZHANG Hongli SHAN Xiaoyan WANG Jie LI Yinhu LI Yingkun HUANG

Abstract ［Objectives］This study was conducted to screen high-efficiency compound formulations and precise application technologies for the prevention and control of sugarcane brown rust.

［Methods］ Zineb, dinconazole, mancozeb, azoxystrobin, pyraclostrobin, difenoconazole·azoxystrobin, chlorothalonil and carbendazim were selected for field efficacy tests.

［Results］ Four formulations, (65% zineb WP 1 500 g+75% chlorothalonil WP 1 500 g+potassium dihydrogen phosphate 2 400 g+agricultural synergist 300 ml)/hm2, (12.5% dinconazole WP 1 500 g +75% chlorothalonil WP 1 500 g+potassium dihydrogen phosphate 2 400 g+agricultural synergist 300 ml)/hm2, (80% mancozeb WP 1 500 g+75% chlorothalonil WP 1 500 g+potassium dihydrogen phosphate 2 400 g+agricultural synergist 300 ml)/hm2 and (30% difenoconazole·azoxystrobin SC 900 ml+potassium dihydrogen phosphate 2 400 g+agricultural synergist 300 ml) had good control efficacy on sugarcane brown rust, and showed disease indexes all below 18.79 and control efficacy over 80.53%. The four formulations are ideal high-efficiency compound formulations for the prevention and control of sugarcane brown rust. They can be sprayed manually and by unmanned aerial vehicles on the foliar surface from July to August, once every 7 to 10 d, continuously for 2 times.

［Conclusions］ This study provides new technical support for accurate and efficient prevention and control of sugarcane rust.

Key words Sugarcane; High-efficiency compound formulation; Precise application; Brown rust; Control efficacy evaluation

Received: March 26, 2022  Accepted: May 29, 2022

Supported by China Agriculture Research System of MOF and MARA (CARS-170303); Yunling Industrial Technology Leading Talent Training Project (2018LJRC56); Special Fund for the Construction of Modern Agricultural Industry Technology System in Yunnan Province; Nanhua Research and Development Institution-Enterprise Cooperation Project.

Wenfeng LI (1964-), female, P. R. China, researcher, devoted to research about sugarcane diseases.

*Corresponding author. E-mail: huangyk64@163.com.

Sugarcane brown rust caused by Puccinia melanocephala H.Sydow & P. Sydow. is a worldwide fungal disease that seriously affects sugarcane production［1-3］. The disease was first reported in Java, Indonesia in 1890［3-4］, and is now distributed in many sugarcane-growing countries and regions in the world and often prevalent, causing disasters and huge economic losses［1,5-8］. Sugarcane brown rust became prevalent in the Gengma sugarcane area of Yunnan in 1982［9］, and then it has been reported and distributed in various sugarcane planting areas in mainland China［10-13］. For many years, sugarcane brown rust has occurred frequently in the main sugarcane-producing areas in China, and it is one of the most serious fungal diseases affecting sugarcane［14-17］. From 2015 to 2018, the susceptible varieties Yuetang 60, Dezhe 03-83, Brazil 45, Liucheng 03-1137 and Guitang 29 were planted on a large scale in the main sugarcane producing areas of Yunnan and Guangxi. Coupled with the long duration of early rainy seasons and the large-scale outbreaks of sugarcane brown rust caused by rainy and high humidity, the reductions in yield and sugar content are serious［2,17］, and brown rust has become the main obstacle to the high-quality development of the cane sugar industry.

At present, most studies on sugarcane brown rust are the isolation and identification of causative pathogens, the biological characteristics of pathogens, the phylogenetic analysis of pathogen populations and the detection of disease resistance genes［11-19］. Few scholars have made preliminary investigation, analysis and exploration on the occurrence of damage, variety resistance and prevention and control［12-17］. However, the research on the prevention and control of sugarcane brown rust is relatively lagging behind, and there are few explorations on the chemical control of sugarcane brown rust. Especially, the practice of field efficacy screening and demonstration application has not been reported. Nowadays, in view of the large-scale outbreak of brown rust on sugarcane and the prevention and control problems, sugarcane farmers lack effective and ideal fungicides to choose from, and the types, doses, and time of fungicides used are unreasonable, and the overall prevention and control effect is poor. In order to screen high-efficiency compound formulations and precise application technologies for the prevention and control of sugarcane brown rust, from 2018 to 2019, efficacy tests by artificial foliar spraying and production demonstration verification by UAV (unmanned aerial vehicle) flight prevention  were carried out on sugarcane brown rust in high-incidence areas including Nanhua Gengma, Huaqiao, Mengyong and Mengsheng Company in Lincang City, Yunnan Province and Menglian Changyu Company, aiming to provide new products and new technical support for the accurate efficient prevention and control of sugarcane brown rust disease.

Materials and Methods

Test agents and sources

The test gents were 65% zineb WP (Dongguan Ruidefeng Biotechnology Co., Ltd., Guangdong Province), 12.5% dinconazole WP (Jiangsu Huifeng Agrochemical Co.,Ltd.), 80% mancozeb WP  (Guangdong Yuantian Bioengineering Co., Ltd.), 25% azoxystrobin EC (Fumin Ecological Agricultural Technology Co., Ltd.), 25% pyraclostrobin suspending agent (Shandong Huimin Vanda Biological Technology Co., Ltd.), 30% difenoconazole·azoxystrobin suspending agent (Shandong Huimin Vanda Biological Technology Co., Ltd), 75% chlorothalonil WP (Guangzhou Agrochemical Factory), and 50% carbendazim WP (Guangzhou Agrochemical Factory).

Control object

The object was sugarcane brown rust induced by Puccinia melanocephala H.Sydow ＆ P. Sydow.

Generation situation of test sites

The test sites were located in the sugarcane areas of Nanhua Gengma, Huaqiao, Mengyong and Mengsheng Company in Lincang City, Yunnan Province and Menglian Changyu Company. The experimental sites had been continuously planted with sugarcane for many years, and the sugarcane varieties were ‘Yuetang 60’ and ‘Liucheng 03-1137’, which are highly susceptible to brown rust. The plants were newly planted or ratoon cane, with a row spacing of 1 m. In dry land, the soil was brick red soil with medium fertility, and water and fertilizer management and sugarcane growth were uniform.

Formulation screening tests

In 2018, formulation screening tests were carried out in the areas with high incidence of sugarcane rust in Nanhua Gengma, Huaqiao, Mengyong and Mengsheng Company in Lincang City, Yunnan Province and Menglian Changyu Company, respectively. The test formulations were as follows: treatment 1 (65% zineb WP 1 500 g+75% chlorothalonil WP 1 500 g+potassium dihydrogen phosphate 2 400 g+agricultural synergist 300 ml)/hm2, treatment 2 (12.5% dinconazole WP 1 500 g+75% chlorothalonil WP 1 500 g+potassium dihydrogen phosphate 2 400 g+agricultural synergist 300 ml)/hm2, treatment 3 (80% mancozeb WP 1 500 g+potassium dihydrogen phosphate 2 400 g+agricultural synergist agent 300 ml)/hm2, treatment 4 (25% azoxystrobin EC 1 200 ml+potassium dihydrogen phosphate 2 400 g+agricultural synergist 300 mL)/hm2, treatment 5 (25% pyraclostrobin SC 600 ml+potassium dihydrogen phosphate 2 400 g+agricultural synergist 300 ml)/hm2, treatment 6 (30% difenoconazole·azoxystrobin SC 900 ml+potassium dihydrogen phosphate 2 400 g+agricultural synergist 300 ml)/hm2, and control formulas: treatment 7 (75% chlorothalonil WP 1 500 g+potassium dihydrogen phosphate 2 400 g+agricultural synergist 300 ml)/hm2 and treatment 8 (50% carbendazim WP 1 500 g+potassium dihydrogen phosphate 2 400 g+agricultural synergist 300 ml)/hm2, and CK (blank control), a total of 9 treatments, each having 3 repetitions, forming 27 plots, each of which had an area of 66 m2. The experiment adopted randomized block arrangement. During the onset period in early July, each formulation at the set dosage per hectare was mixed with 900 kg of water according to the experimental treatment, and artificial foliar spraying was carried out with an electric knapsack sprayer, once every 7-10 d, continuously for 2 times. The blank control was not treated with any agrochemicals, only sprayed with the same amount of water, and other agricultural management was the same.

Demonstration of production with test formulations

According to the screening and evaluation results of the formulations in 2018, the formulations with better control effects were selected in 2019 for the demonstration of formulation production in the high incidence areas of sugarcane brown rust of Nanhua Gengma, Huaqiao, Mengyong and Mengsheng Company in Lincang, Yunnan Province and Menglian Changyu Company. The demonstrated formulations were as follows: treatment 1 (65% zineb WP 1 500 g+75% chlorothalonil WP 1 500 g+potassium dihydrogen phosphate 2 400 g+agricultural synergist 300 ml)/hm2, (12.5% dinconazole WP 1 500 g+75% chlorothalonil WP 1 500 g+potassium dihydrogen phosphate 2 400 g+agricultural synergist 300 ml)/hm2, treatment 3 (80% mancozeb WP 1 500 g+potassium dihydrogen phosphate 2 400 g+agricultural synergist agent 300 ml)/hm2, treatment 6 (30% difenoconazole·azoxystrobin SC 900 ml+potassium dihydrogen phosphate 2 400 g+agricultural synergist 300 ml)/hm2 and CK (blank control), five treatments in total, each having a demonstration area of 15 hm2. During the disease period in early July, the agents in quantities per hectare according to the demonstration treatment setting were added with 4 500 ml of special adjuvant for flight control and 16 500 ml of water, and sprayed to leaves in a mode of drone flight control, once every 7-10 d, twice in total. The blank control was not treated with any agents, only sprayed with the same amount of water. Other agricultural management was the same.

Investigation of control efficacy

In September and October of each year, when the disease fully developed in the blank control, each treatment plot of the screening test was sampled at 3 points, and 20 plants were continuously investigated at each point, totaling 60 plants; and 4 representative fields were selected for each treatment in the production demonstration, and each field was sampled at 3 points, at each of which 20 plants were continuously investigated, totaling 60 plants, for the visual observation of the disease status and infection area percentage of all fully expanded leaves, the recording of total number of investigated plants and the number of diseased plants at all levels and the calculation of disease index and control effect. According to the standard of J.C. Comstock (1992), the disease grading of sugarcane brown rust was carried out: level 1: leaves are asymptomatic, level 3: lesions account for 0% to 25% of the leaf area, level 5: lesions account for 26%-50% of the leaf area, level 7: lesions account for 51% to 75% of the leaf area, and level 9: lesions account for 76%-100% of the leaf area［7］.

Disease index=∑［Number of diseased plants at each level×Corresponding level］/［Total number of plants investigated ×The highest level］×100

Control efficacy(%)=(Disease index in treatment area-Disease index in control area)/Disease index in control area×100

Data processing

The investigation results were compared for significance of differences using SAS 9.0 statistical analysis software by the Duncan’s new multiple range method.

Results and Analysis

Control efficacy of various formulations on sugarcane brown rust

As shown in Table 1, the four formulations, treatment 1 (65% zineb WP 1 500 g+75% chlorothalonil WP 1 500 g+potassium dihydrogen phosphate 2 400 g+agricultural synergist 300 ml)/hm2, treatment 2 (12.5% dinconazole WP 1 500 g+75% chlorothalonil WP 1 500 g+potassium dihydrogen phosphate 2 400 g+agricultural synergist 300 ml)/hm2, treatment 3 (80% mancozeb WP 1 500 g+potassium dihydrogen phosphate 2 400 g+agricultural synergist agent 300 ml)/hm2 and treatment 6 (30% difenoconazole·azoxystrobin SC 900 ml+potassium dihydrogen phosphate 2 400 g+agricultural synergist 300 ml)/hm2 had good control effects on sugarcane brown rust in the screening tests in the five sugarcane areas, and the control effects were stable and consistent. The average control efficacy of the four formulations was, respectively, 86.93%, 86.46%, 87.2%, and 81.17%, which were significantly higher than those of other formulation treatments and control formulation treatment 7 (75% chlorothalonil WP 1500 g+potassium dihydrogen phosphate 2 400 g+agricultural synergist 300 ml)/hm2 and treatment 8 (50% carbendazim WP 1 500 g+potassium dihydrogen phosphate 2 400 g+agricultural synergist 300 ml)/hm2, and there were no significant differences between the later three. The average control efficacy of treatment 4 (25% azoxystrobin EC 1 200 ml+potassium dihydrogen phosphate 2 400 g+agricultural synergist 300 mL)/hm2 and treatment 5 (25% pyraclostrobin SC 600 ml+potassium dihydrogen phosphate 2 400 g+agricultural synergist 300 ml)/hm2 was, respectively, 71.24% and 71.63%, which were slightly better than that of control formulation treatment 7 (75% chlorothalonil WP 1 500 g+potassium dihydrogen phosphate 2 400 g+agricultural synergist 300 mL)/hm2, but significantly higher than the average efficacy of treatment 8 (50% carbendazim WP 1 500 g+potassium dihydrogen phosphate 2 400 g+agricultural synergist 300 ml)/hm2.

Control efficacy of various formulations on sugarcane brown rust in production demonstration

As can be seen from Table 2, the four formulations, treatment 1 (65% zineb WP 1 500 g+75% chlorothalonil WP 1 500 g+potassium dihydrogen phosphate 2 400 g+agricultural synergist 300 ml)/hm2, treatment 2 (12.5% dinconazole WP 1 500 g+75% chlorothalonil WP 1 500 g+potassium dihydrogen phosphate 2 400 g+agricultural synergist 300 ml)/hm2, treatment 3 (80% mancozeb WP 1 500 g+potassium dihydrogen phosphate 2 400 g+agricultural synergist agent 300 ml)/hm2, and treatment 6 (30% difenoconazole·azoxystrobin SC 900 ml+potassium dihydrogen phosphate 2 400 g+agricultural synergist 300 ml)/hm2 achieved good control effects on sugarcane brown rust in the production demonstration by UAV flight control in the five sugarcane areas, and the control effects were stable and consistent. The average disease indexes of the four formulations were 13.64, 14.79, 12.84, and 18.79, respectively, and their average control efficacy was 85.87%, 84.68%, 86.7%, and 80.53%, respectively.

Conclusions and Discussion

The results of this study showed that such four compound formulations as (65% zineb WP 1 500 g+75% chlorothalonil WP 1 500 g+potassium dihydrogen phosphate 2 400 g+agricultural synergist 300 ml)/hm2, (12.5% dinconazole WP 1 500 g+75% chlorothalonil WP 1 500 g+potassium dihydrogen phosphate 2 400 g+agricultural synergist 300 ml)/hm2, (80% mancozeb WP 1 500 g+potassium dihydrogen phosphate 2 400 g+agricultural synergist agent 300 ml)/hm2, and (30% difenoconazole·azoxystrobin SC 900 ml+potassium dihydrogen phosphate 2 400 g+agricultural synergist 300 ml)/hm2 achieved a good field effect in the manual spraying test and UAV flight control demonstration verification on sugarcane brown rust, and the control efficacy was stable and consistent, so they are ideal high-efficiency compound formulations for the prevention and control of sugarcane brown rust disease. In the early stage of the disease from July to August, one of them can be chosen and added with 900 kg of water per hectare, and the liquid can be used for artificial foliar spraying with an electric knapsack sprayer or a motorized high-pressure sprayer, or 4 500 ml of special adjuvant and 16 500 ml of water are added per hectare for UAV flight control, once every 7-10 d, continuously for two times. The control efficacy on sugarcane brown rust disease can reach more than 80%, and the disease index can be controlled below 19%. Furthermore, the effect of increasing yield and increasing sugar is remarkable.

Zineb, dinconazole, mancozeb and chlorothalonil have systemic treatment or protective effects. Their action sites and mechanisms complement each other, and their combined application is highly complementary and has obvious synergistic effects. Such application method also delays the development of drug resistance of pathogens while reducing the frequency and dosage of drug application, reducing residues in crops and soil and improving ecological security. The results of this study showed that such four compound formulations as (65% zineb WP 1 500 g+75% chlorothalonil WP 1 500 g+potassium dihydrogen phosphate 2 400 g+agricultural synergist 300 ml)/hm2, (12.5% dinconazole WP 1 500 g+75% chlorothalonil WP 1 500 g+potassium dihydrogen phosphate 2 400 g+agricultural synergist 300 ml)/hm2, (80% mancozeb WP 1 500 g+potassium dihydrogen phosphate 2 400 g+agricultural synergist agent 300 ml)/hm2, and (30% difenoconazole·azoxystrobin SC 900 ml+potassium dihydrogen phosphate 2 400 g+agricultural synergist 300 ml)/hm2 had a very obvious synergistic effect in the prevention and control of sugarcane brown rust, with control efficacy all over 81.17%, which was significantly higher than that of carbendazim or chlorothalonil (49.31%, 66.14%). According to the experimental observation, the four compound formulations are safe and harmless to beneficial organisms in sugarcane orchards, do not affect the environment and ecology, and also have a good effect on the combined treatment of sugarcane brown streak disease, tip rot, red rot and other complex infections, thereby worthing popularizing and applying in sugarcane areas in a large area.

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