Effects of Spraying Plant Extract Mixture on Growth and Development and Diseases of Flue-cured Tobacco

Zhigao Zhang

Fuzhou Tobacco Company in Jiangxi Province,Fuzhou 344000,China

Abstract [Objective]The paper was to study the effects of plant extract mixture on growth and development,photosynthetic indexes and disease control of flue-cured tobacco.[Method]Using field test method,a total of five treatments were designed in the test,including T1(control,conventional pesticide control),T2(conventional pesticide control+spraying plant extract mixture at 15 and 30 d post transplanting),T3(conventional pesticide control+spraying plant extract mixture at 15,30 and 45 d post transplanting),T4 (conventional pesticide control+spraying plant extract mixture at 15,30,45 and 60 d post transplanting),and T5(conventional pesticide control+spraying plant extract mixture at 15,30,45,60 and 75 d post transplanting).In addition,flue-cured tobacco in treatments T2-T5 were sprayed with antiviral agent once at 30 d post transplanting,and sprayed with quality promoting agent at 30 and 75 d post transplanting,respectively.[Result]The agronomic traits and photosynthetic indexes of all treatments were improved by spraying plant extract mixture,and those in T5 treatment were the best.Spraying plant extract mixture had significant control effect on brown spot;the disease index in T5 treatment was the lowest,and the control effect was the best.The results showed that spraying plant extract mixture promoted the growth and development of flue-cured tobacco,reduced the disease index of brown spot,and improved the quality of tobacco leaves.[Conclusion]Spraying plant extract mixture has positive effect on growth and development and disease control of flue-cured tobacco.

Keywords Flue-cured tobacco;Plant extract mixture;Agronomic characters;Brown spot

In recent years,continuous cropping obstacle of tobacco is increasingly severe,which not only aggravates the occurrence of diseases and pests,but also reduces the quality of flue-cured tobacco[2].As a result,people are becoming more and more dependent on the use of pesticides and fertilizers,the resistance of pests and bacteria increases correspondingly,and the soil environment is also damaged[3-4].Therefore,it is particularly important to explore the effects of pure botanical agents on the prevention and control of rhizome diseases in flue-cured tobacco field and the quality of tobacco leaves[5-7].The effects of plant extract mixture on the growth,development and diseases of flue-cured tobacco were studied through plot test,in order to provide reliable basis for realizing sustainable development of tobacco production in Fuzhou tobacco area of Jiangxi Province.

1 Materials and Methods

1.1 Experimental conditions The trial was carried out in 2020 in Zhangshu Village,Ganzhu Town,Guangchang County,Jiangxi Province,116°22′40″E and 26°53′46″N.The experiment field was dryland of purple soil with medium and uniform fertility,flat ground,convenient drainage and irrigation,and no highly residual herbicides were used in the previous crop.

1.2 Materials Yunyan 87 was selected as the tested variety.Plant extract mixture(herbal antifungal agent),herbal antiviral agent and quality promoting agent provided by Zunyi Jinxi Agricultural Science and Technology Co.,Ltd.were selected as the tested agents.The main ingredients of the agents were Artemisia apiacea,Forsythia suspense,Sophora flavescens,Stemona japonica,Cortex Phellodendron chinense,Artemisia argyi and Cnidium monnieri.

1.3 Experimental methods Based on conventional pesticide control against pests and diseases,a total of five treatments were designed in the test,including T1(control,conventional pesticide control),T2(conventional pesticide control+spraying plant extract mixture at 15 and 30 d post transplanting),T3(conventional pesticide control+spraying plant extract mixture at 15,30 and 45 d post transplanting),T4(conventional pesticide control+spraying plant extract mixture at 15,30,45 and 60 d post transplanting),and T5(conventional pesticide control+spraying plant extract mixture at 15,30,45,60 and 75 d post transplanting).Each plot covered an area of 40-50 m2.All plots were in randomized block arrangement,three replicates each treatment,with a total of 15 plots.In addition,flue-cured tobacco in treatments T2-T5 were sprayed with antiviral agent once at 30 d post transplanting,and sprayed with quality promoting agent at 30 and 75 d post transplanting,respectively.Field tobacco planting density,fertilization and other field management were conducted according to local high quality tobacco production technology plan,and all agricultural operations were carried out on the same day.

1.4 Measurement items and methods

1.4.1 Investigation of agronomic traits and SPAD.According to YC/T142-2010 Survey and Measurement Methods for Tobacco Agronomic Traits,the plant height,maximum leaf length,maximum leaf width,number of effective leaves and agronomic traits of tobacco plants were measured in resettling stage,squaring stage and topping stage,respectively.Five tobacco leaves were selected from fixed points of each plot to determine SPAD-502plus.

1.4.2 Determination of photosynthetic indexes.In resettling stage,squaring stage and topping stage,the central leaves of five tobacco plants with consistent growth were selected from each plot at 9:00 am-12:00 am of the day with sufficient light conditions to determine photosynthetic indexes,respectively.The photosynthetic indexes were determined by CI-340 portable photosynthesis meter.

1.4.3 Disease investigation.Disease investigation and classification were carried out according to national standards.

1.4.4 Data analysis and processing.All data were statistically analyzed by Excel2007 and SPSS24.0,and plotted by Origin2018.

2 Results and Analysis

2.1 Effects of different treatments on agronomic traits of flue-cured tobacco As shown in Table 1,the agronomic traits of T3,T4 and T5 treatments were higher than that of T1 treatment(control)in the resettling stage,and the maximum leaf length of T5 treatment was significantly higher than that of T1 treatment(control),while the increase effect of other indexes was not obvious.In the squaring stage,the plant height,maximum leaf length,maximum leaf width and maximum leaf area of T4 and T5 treatments were significantly higher than those of T1treatment(control).In the topping stage,the agronomic traits of all treatments were higher than those of T1 treatment (control),and the plant height of T5 treatment was significantly higher than those of other treatments;the maximum leaf length of T5 treatment was significantly higher than that of T1 treatment(control).In the initial baking period,the agronomic traits of all treatments were higher than those of T1 treatment(control).Except for the number of effective leaves,the other agronomic traits of T5 treatment were significantly higher than those of T1 treatment(control),and the agronomic traits of T2,T3 and T4 treatments were all improved compared with T1 treatment(control).

Table 1 Effects of different treatments of plant extract mixture on agronomic traits of flue-cured tobacco in different stages

2.2 Effects of different treatments on SPAD value of flue-cured tobacco As shown in Table 2,the SPAD value of fluecured tobacco in various treatments showed an increasing trend in the resettling stage,and the SPAD values of T2,T3,T4 and T5 treatments were significantly higher than that of T1 treatment(control);the SPAD value of T4 and T5 treatments were significantly higher than those of T3 and T2 treatments,while there was no significant difference in SPAD value between T2 and T3 treatments,or between T4 and T5 treatments.In the squaring stage stage,the SPAD values of all treatments successively were T5＞T4＞T3＞T1＞T2,in which the SPAD values of T4 and T5 treatments were significantly higher than those of T1,T2 and T3 treatments,and there was no significant difference among other treatments.In the topping stage,the SPAD values of all treatments successively were T5＞T4＞T3＞T2＞T1;the SPAD values of T3,T4 and T5 treatments were significantly higher than that of T1 treatment(control);there was no significant difference in SPAD value between T2 treatment and T1 treatment,while the SPAD values of T3,T4 and T5 treatments were significantly higher than that of T2 treatment;the SPAD value of T5 treatment was the largest,which in-creased by7.46% compared with T1 treatment(control).In the initial baking stage,the SPAD values of T2,T3 and T4 had no significant difference with that of T1 treatment;the SPAD value of T5 treatment was significantly higher than that of T1 treatment;and the SPAD values of all treatments successively were T5＞T4＞T2＞T3＞T1.

Table 2 Effects of different treatments of plant extract mixture on SPAD value of flue-cured tobacco in different stages

2.3 Effects of different treatments on photosynthetic indexes As shown in Fig.1,there was no significant difference in photosynthetic rate and stomatal conductance among different treatments in the resettling stage,while there were significant difference in intercellular carbon dioxide concentration and transpiration rate between T5 and T1 treatments.The intercellular carbon dioxide concentrations of T2,T3,T4 and T5 treatments were increased by 5.87%,9.73%,12.7%and 21%compared with T1 treatment.In the squaring stage,the photosynthetic rates of T4 and T5 treatments had significant difference with that of T1 treatment,and the photosynthetic rates of various treatments successively were T5＞T4＞T3＞T2＞T1.The intercellular carbon dioxide concentration in T5 treatment was significantly higher than those in T2,T3,T4 and T1 treatments,while there was no significant difference between T2,T3 and T4 treatments.The stomatal conductance of T3,T4 and T5 treatments were significantly higher than those of T1 and T2 treatments,and there was no significant difference in transpiration rate among various treatments.In the topping stage,the other indexes of T3,T4 and T5 treatments were significantly higher than that of T1 treatment except stomatal conductance,and intercellular carbon dioxide concentration and transpiration rate showed an increasing trend.

2.4 Effects of different treatments on the occurrence of diseases As shown in Table 3,the disease indexes of brown spot in all treatments sprayed with plant extract mixture were lower than that of T1 treatment in the survey on May 25.With the increase of spraying times,the disease index of brown spot in all treatments gradually decreased.The disease index of T5 treatment decreased by 16.56%compared with that of T1 treatment,and its control effect was the best.The disease indexes of brown spot in all treatments sprayed with plant extract mixture were lower than that of T1 treatment in the survey on June 10.The disease indexes of T2,T3,T4 and T5 treatments showed a decreasing trend,and the control effect also increased obviously.The disease index in T5 treatment was the lowest(9.85)and the control effect was the highest(39.90%).The disease indexes of T2,T3,T4 and T5 treatments were all lower than that of T1 treatment on June 25,and the disease index of T4 treatment was the lowest,which was 35.30%lower than that of T1 treatment,while the control effect was the highest(35.30%).

Table 3 Effects of different treatments of plant extract mixture on flue-cured tobacco brown spot

3 Discussion

Plant extract mixture uses water extracts of Chinese medicinal materials such as A.apiacea and S.flavescens to substitute pesticides,which can achieve the effects of fertilizer reduction and pest control,forming a new mode of"traditional Chinese medicine agriculture"with high safety,high yield and quality,and high competitiveness[7].The results of this study showed that spraying plant extract mixture for different times had certain influence on agronomic characters of flue-cured tobacco.The maximum leaf length,leaf width and leaf area of flue-cured tobacco were significantly increased by spraying plant extract mixture in the resettling stage and the squaring stage.In the topping stage,the plant height of T5 treatment was significantly higher than that of T1 treatment,and there were no significant differences in the number of effective leaves,maximum leaf length,maximum leaf width and leaf area among various treatments.In the initial baking stage,the plant height,maximum leaf length,maximum leaf width and leaf area of each treatment sprayed with plant extract mixture were significantly higher than those of T1 treatment.The comprehensive results of various stages showed that plant extract mixture combined with antiviral agents and quality promoting agents significantly improved the growth and development of tobacco plants,which also promoted SPAD value and photosynthetic index of flue-cured tobacco to some extent.The results suggested that spraying plant extract mixture promoted the metabolism of plants,ensured the healthy growth of plants,and induced plants to enhance immune ability.

Spraying plant extract mixture had certain inhibitory effect on the occurrence of flue-cured tobacco diseases,and the inhibitory effect increased with the increase of spraying times,while spraying plant extract mixture for five times received the best effect.In this test,brown spot was the major disease of flue-cured tobacco,and no other diseases occurred in the field.The occurrence of brown spot in the treatment sprayed with plant extract mixture was significantly reduced compared with the control.In terms of disease index of brown spot,the disease index of T5 treatment decreased by 1.00,6.54 and 8.91 respectively compared with the control.In terms of control effect,with the increase of spraying times of plant extract mixture,the control effect against the disease also increased,and T5 treatment showed the best overall performance.Compared with traditional pesticides,plant extract mixture has no side effects and pesticide residues,and reduces the risk of excessive pesticide residues in tobacco production to a certain extent.Therefore,plant extract mixture has a very good prospect.

4 Conclusions

The effect of spraying plant extract mixture was not significant in the early growth stage of flue-cured tobacco.With the advance of growth period and the increase of spraying times,the influence on the growth and development of flue-cured tobacco also increased.The agronomic characters and photosynthetic indexes of flue-cured tobacco were improved in varying degrees after spraying plant extract mixture,and the occurrence and species of diseases during the growth period also reduced.In conclusion,T5 treatment(conventional pesticide control+spraying plant extract mixture at 15,30,45,60 and 75 d post transplanting)had the best effect and performance on the growth,development and disease control of fluecured tobacco.