Evaluation of the Effect of High-efficiency Compound Formulations on the Prevention and Control of Sugarcane Brown Stripe

2022-07-13 20:59WenfengLIXiaoyanWANGHongliSHANRongyueZHANGYinhuLIJieLIYingkunHUANG
农业生物技术(英文版) 2022年3期

Wenfeng LI Xiaoyan WANG Hongli SHAN Rongyue ZHANG Yinhu LI Jie 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 stripe disease. [Methods]Carbendazim, benomyl, chlorothalonil, azoxystrobin, pyraclostrobine and difenoconazole·azoxystrobin were selected for field efficacy tests. [Results] Three formulations, (50% carbendazim WP 1 500 g+75% chlorothalonil WP 1 500 g+potassium dihydrogen phosphate 2 400 g+agricultural synergist 300 ml)/hm, (50% benomyl WP 1 500 g+75% chlorothalonil WP 1 500 g+potassium dihydrogen phosphate 2 400 g+agricultural synergist 300 ml)/hm and (25% pyraclostrobin 600 ml+potassium dihydrogen phosphate 2 400 g+agricultural synergist 300 ml)/hm had good control effects on sugarcane brown stripe disease, and showed disease index below 14.02 and control efficacy above 84.41%. The three formulations are ideal high-efficiency compound formulations for the prevention and control of sugarcane brown stripe disease. 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 brown stripe disease.

Key wordsSugarcane; High-efficiency compound formulation; Precise application; Brown stripe disease; Control efficacy evaluation

Sugarcane brown stripe disease caused by Helminthosporium stenospilum Drechsler is an important fungal disease that damages sugarcane leaves. The main hosts of this pathogen are sugarcane, corn, Sorghum halepense (Linn.) Pers., barnyard grass, foxtail, etc.[1-2]. Sugarcane brown stripe disease was first discovered in Cuba in 1924[3-4], and more than 20 sugarcane-growing countries have reported the disease so far. The disease is widespread around the world in different periods, often causing economic losses to varying degrees[5-7]. Brown stripe disease has been reported in all sugarcane-growing provinces and regions in China, and it generally occurred sporadically before the 1980s[8-12]. In 1975, continuous rainy and humid conditions in Dingan County, Hainan led to the outbreak of brown stripe disease on sugarcane, and the incidence rate in severely diseased areas reached 100%, which seriously affected the normal growth of sugarcane[13]. In 1996 and 1997, due to the long-term rainy season and the planting of high-susceptibility variety ‘Guitang 11’ on a large scale in the Maitreya sugarcane area of Yunnan, brown stripe disease of sugarcane occurred in a large area for two consecutive years, causing serious damage[14]. In 2001, the increase of precipitation in Mengshan County, Guangxi Province from 60% to 160% compared with previous years, coupled with long-term fertilization lacking phosphorus and potassium, resulted in the prevalence of sugarcane brown stripe disease, which was rare in this area for more than 20 years[15]. From 2015 to 2018, susceptible varieties, ‘Xintaitang 25’, ‘Yuetang 93-159’, ‘Guitang 11’, ‘Guitang 02-761’, ‘Guitang 42’ and ‘Yunyin 3’ were planted in large scales, which, coupled with rainy and high humidity, led to large-scale outbreaks of sugarcane brown stripe disease in major sugarcane producing areas such as Lincang, Puer, Yuxi, Banna and Honghe in Yunnan and Yizhou and Chongzuo in Guangxi, causing disasters and serious yield reductions. Sugarcane production is facing increasingly severe disaster threats[2,16-17]. In fields suffering from serious sugarcane brown stripe, the rate of infected sugarcane plants is more than 80%, and at first glance, it looks like "burning". The yield is reduced by 18% to 35% generally, even more than 40% in severe cases, and the sucrose content is reduced by 15% to 30%[2,8]. The outbreak of sugarcane brown stripe disease has become one of the main obstacles to high and stable quality of sugarcane at this stage. Therefore, fully understanding the harm of sugarcane brown stripe disease and the importance of prevention and control and developing and taking effective measures for controlling the outbreak of sugarcane brown stripe disease will be the primary task and fundamental guarantee for promoting the high-quality development of the sugarcane industry.

At present, there are few research reports on sugarcane brown stripe disease at home and abroad, and most of them are preliminary investigations on the occurrence and prevention of the disease[18-21]. A few studies are preliminary investigation, analysis and exploration on the occurrence of damage, variety resistance and prevention and control[21-23]. However, the research on the control of sugarcane brown stripe disease is relatively lagging behind. There have been few explorations on the chemical control of sugarcane brown stripe disease, and especially, the practice of field efficacy screening and demonstration application has not yet been reported. Nowadays, in view of the large-scale outbreak of sugarcane brown stripe disease and the prevention and control problems, sugarcane farmers lack effective and ideal agrochemicals to choose from, and the types, doses and time of agrochemicals 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 stripe disease, from 2018 to 2019, efficacy tests and production demonstration verification were carried out on sugarcane brown stripe disease using 50% carbendazim WP, 50% benomyl WP, 75% chlorothalonil WP, 25% azoxystrobin EC, 25% pyraclostrobin SC and 30% difenoconazole·azoxystrobin SC by artificial foliar spraying in high-incidence areas including Nanhua Gengma, Huaqiao, Mengyong and Shuangjiang 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 stripe disease.

Materials and Methods

Test agents and sources

The test gents were 50% carbendazim WP (Guangzhou Agrochemical Factory); 50% benomyl WP (Xuzhou Shennong Chemical Co., Ltd.); 75% chlorothalonil WP (Guangzhou Agrochemical Factory); 25% % azoxystrobin EC (Fumin Ecological Agricultural Technology Co., Ltd.); 25% pyraclostrobin suspending agent (Shandong Huimin Vanda Biotechnology Co., Ltd.), 30% difenoconazole·azoxystrobin suspending agent (Shandong Huimin Vanda Biotechnology Co., Ltd).

Object of prevention

The object was sugarcane brown stripe induced by Helminthosporium stenospilum Drechsler.

Generation situation of test sites

The test sites were located in the sugarcane areas of Nanhua Gengma, Huaqiao, Mengyong and Shuangjiang 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 ‘Xintaitang 25’ and ‘Yuetang 93-159’, which are highly susceptible to brown stripe disease. The plants were newly planted or stubble 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 20dy, formulation screening tests were carried out in the areas with high incidence of sugarcane brown stripe disease in Nanhua Gengma, Huaqiao, Mengyong and Shuangjiang Company in Lincang City and Menglian Changyu Company, respectively. The test formulations were as follows: treatment 1 (50% carbendazim WP 1 500 g+75% chlorothalonil WP 1 500 g+potassium dihydrogen phosphate 2 400 g+agricultural synergist 300 ml)/hm, treatment 2 (50% benomyl WP 1 500 g+75% chlorothalonil WP 1 500 g+potassium dihydrogen phosphate 2 400 g+agricultural synergist 300 ml)/hm, treatment 3 (25% azoxystrobin EC 1 200 ml+potassium dihydrogen phosphate 2 400 g+agricultural synergist agent 300 ml)/hm, treatment 4 (25% pyraclostrobin SC 600 ml+potassium dihydrogen phosphate 2 400 g+agricultural synergist 300 mL)/hm2, treatment 5 (30% difenoconazole·azoxystrobin SC 900 ml+potassium dihydrogen phosphate 2 400 g+agricultural synergist 300 ml)/hm, control formulas: treatment 6 (75% chlorothalonil WP 1500 g+potassium dihydrogen phosphate 2 400 g+agricultural synergist 300 ml)/hm and treatment 7 (50% carbendazim WP 1 500 g+potassium dihydrogen phosphate 2 400 g+agricultural synergist 300 ml)/hm, and CK (blank control), a total of 8 treatments, each having 3 repetitions, forming 24 plots, each of which had an area of 66 m. The experiment adopted randomized block arrangement. During the onset period in mid-August, 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 two 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 stripe of Nanhua Gengma, Huaqiao, Mengyong and Shuangjiang Company in Lincang, Yunnan Province and Menglian Changyu Company. The demonstrated formulations were as follows: treatment 1 (50% carbendazim WP 1 500 g+75% chlorothalonil WP 1 500 g+potassium dihydrogen phosphate 2 400 g+agricultural synergist 300 ml)/hm, treatment 2 (50% benomyl WP 1 500 g+75% chlorothalonil WP 1 500 g+potassium dihydrogen phosphate 2 400 g+agricultural synergist 300 ml)/hm, treatment 4 (25% pyraclostrobin SC 600 ml+potassium dihydrogen phosphate 2 400 g+agricultural synergist) and CK (blank control), 4 treatments in total, each having a demonstration area of 20 hm. During the disease period in mid-August, 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 November and December 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 Yang et al.[23], the disease grading of sugarcane brown stripe 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%-40% of the leaf area, level 7: lesions account for 41% to 65% of the leaf area, and level 9: lesions account for 66%-100% of the leaf area.

Disease index=[(Number of diseased plants at each level×Corresponding level)/(Total number of plants investigated×The highest level)]×100% (1)

Control efficacy=(Disease index in treatment area/Disease index in control area)×100% (2)

Data processing

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

Results and Analysis

Control effects of various formulations on sugarcane brown stripe disease

As shown in Table 1, the 3 formulations, treatment 1 (50% carbendazim WP 1 500 g+75% chlorothalonil WP 1 500 g+potassium dihydrogen phosphate 2 400 g+agricultural synergist 300 ml)/hm, treatment 2 (50% benomyl WP 1 500 g+75% chlorothalonil WP 1 500 g+potassium dihydrogen phosphate 2 400 g+agricultural synergist 300 ml)/hm, treatment 4 (25% pyraclostrobin SC 600 ml+potassium dihydrogen phosphate 2 400 g+agricultural synergist 300 ml)/hm had good control effects on sugarcane brown stripe in the screening tests in the five sugarcane areas, and the control effects were stable and consistent. The average control efficacy of the three formulas was, respectively, 88.47%, 87.61%, and 85.91%, which were significantly higher than those of other formulation treatments and control formulation treatment 6 (75% chlorothalonil WP 1 500 g+potassium dihydrogen phosphate 2 400 g+agricultural synergist 300 ml)/hm and treatment 7 (50% carbendazim WP 1 500 g+potassium dihydrogen phosphate 2 400 g+agricultural synergist 300 ml)/hm, and there were no significant differences between the three. The average control efficacy of treatment 5 (30% difenoconazole·azoxystrobin SC 900 ml+potassium dihydrogen phosphate 2 400 g+agricultural synergist 300 ml)/hm was 72.58%, slightly better than that of the control formulation treatment 7 (50% carbendazim WP 1 500 g+potassium dihydrogen phosphate 2 400 g+agricultural synergist 300 ml)/hm2, but significantly higher than that of the control formulation treatment 6 (75% chlorothalonil WP 1 500 g+potassium dihydrogen phosphate 2 400 g+agricultural synergist 300 ml)/hm. Treatment 3 (25% azoxystrobin EC 1 200 ml+potassium dihydrogen phosphate 2 400 g+agricultural synergist 300 ml)/hm had the worst average control efficacy of 56.75%, which was not significantly different from that of treatment 6 (75% chlorothalonil WP 1 500 g+potassium dihydrogen phosphate 2 400 g+agricultural synergist 300 ml)/hm.

Control effects of various formulations on sugarcane brown stripe in production demonstration

As can be seen from Table 2, the 3 formulations, treatment 1 (50% carbendazim WP 1 500 g+75% chlorothalonil WP 1 500 g+potassium dihydrogen phosphate 2 400 g+agricultural synergist 300 ml)/hm, treatment 2 (50% benomyl WP 1 500 g+75% chlorothalonil WP 1 500 g+potassium dihydrogen phosphate 2 400 g+agricultural synergist 300 ml)/hm and treatment 4 (25% pyraclostrobin SC 600 ml+potassium dihydrogen phosphate 2 400 g+agricultural synergist 300 ml)/hm achieved good control effects on sugarcane brown stripe disease in production demonstration by UAV flight control, and the control effects were stable and consistent. The average disease index of the three formulas was 11.25, 12.54, and 14.02, respectively, and their average control efficacy was 87.49%, 86.05% and 84.41%, respectively.

Conclusions and Discussion

The results of this study showed that such three compound formulations (50% carbendazim WP 1 500 g+75% chlorothalonil WP 1 500 g+potassium dihydrogen phosphate 2 400 g+agricultural synergist 300 ml)/hm, (50% benomyl WP 1 500 g+75% chlorothalonil WP 1 500 g+potassium dihydrogen phosphate 2 400 g+agricultural synergist 300 ml)/hm and (25% pyraclostrobin SC 600 ml+potassium dihydrogen phosphate 2 400 g+agricultural synergist 300 ml)/hm showed a good field effect in the manual spraying test and unmanned aerial vehicle flight control production demonstration and verification on sugarcane brown stripe disease, and the control effect was stable and consistent, so they are ideal high-efficiency compound formulations for the prevention and control of sugarcane brown stripe 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 unmanned aerial vehicle flight control, once every 7-10 d, continuously for two times. The control efficacy on sugarcane brown stripe disease can reach more than 84.41%, and the disease index can be controlled below 14.02%. Furthermore, the effect of increasing production and increasing sugar is remarkable.

Carbendazim, benomyl 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. In this study, aiming at the prevention and control of brown stripe disease in the large elongation period of sugarcane, such three compound formulations as (50% carbendazim WP 1 500 g+75% chlorothalonil WP 1500 g+potassium dihydrogen phosphate 2 400 g+agricultural synergist 300 ml)/hm, (50% benomyl WP 1 500 g+75% chlorothalonil WP 1 500 g+potassium dihydrogen phosphate 2 400 g+agricultural synergist 300 ml)/hm and (25% pyraclostrobin SC 600 ml+dihydrogen phosphate Potassium 2 400 g+agricultural synergist 300 ml)/hm2 were screened out, and the best spraying period and precise spraying technology were analyzed clarified, which provides new formulations and new technology support for precise prevention and control of sugarcane brown stripe disease. The results showed that the synergistic effect of the three formulations in the prevention and control of sugarcane brown stripe disease was extremely significant, and the control effects were over 85.91%, significantly higher than that of the single use of carbendazim or chlorothalonil (68.02%, 57.49%), while the cost of drugs per hectare was only 270 yuan. It can be seen that the three formulations are ideal efficient complex formulations for the prevention and control of sugarcane brown stripe disease, and they are suitable for UAV flight control and have high operating efficiency. It can effectively solve the problems of late spraying of high-stem crops and labor shortage, and opens up a new, simple and efficient way for the effectively prevention and control of sugarcane diseases in the middle and late stages. According to the experimental observation, the three compound formulations are safe and harmless to beneficial organisms in sugarcane plantations, do not affect the environmental ecology, and also have a good effect on the combined treatment of sugarcane top rot, red rot, brown spot and other compound infections. They are worth popularizing and applying in a large area in sugarcane areas, so as to realize the effects of one drug for multiple prevention, economical efficiency, agrochemical reduction and harm control and sugarcane quality and efficiency improvement.

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Editor: Yingzhi GUANG Proofreader: Xinxiu ZHU