Allicin + Kasuramycin: new strategy for green prevention and control of bacterial diseases under the trend of "Dual reduction in chemical fertilizers and chemical pesticides"

1. Introduction

In recent years, global climate change has led to more frequent occurrence of plant bacterial diseases, such as rice bacterial leaf streak, cucumber bacterial angular leaf spot and bacterial root rot. Due to the characteristics of outbreak, prevalence, destructiveness and difficulty in control of plant bacterial diseases, chemical control is a necessary measure. According to a report released by Market Research Future (MRFR), the value of the global fungicide market will maintain a growth trend from 2020 to 2023. The demand for fungicides in major global agricultural regions and countries such as the United States, European Union, and Brazil is expected to continue to rise during this period. Chloronitrobenzenes (such as chloronitrophenol, trichloronitrobenzene), copper-based fungicides (such as copper sulfate, copper oxide), iron-based fungicides (such as ferrous sulfate), zinc sulfate fungicides (such as Zinc sulfate, zinc ammonium sulfate), amino acid fungicides (such as amino acid copper, amino acid zinc), cyclohexanone fungicides (such as Cyclohexanone, Cyclohexanone oxide), triazole fungicides (such as Azoxystrobin, Tebuconazole, Carbendazim), phenolic fungicides (such as chlorophenol, cresol), amide fungicides (such as benzamide, piroxamide) and other products will still be the main fungicides for disease control. In China, due to the policy adjustment and the promotion of ecological agriculture, the use of fungicides in China may decline.

The long-term incorrect use of chemical pesticides has not only brought serious environmental pollution problems, but also greatly increased the resistance of target diseases, seriously affecting the quality and safety of agricultural products and biodiversity, and affecting the sustainable development of human society. Considering the serious disease resistance and the risk of personal health problems, Streptomycin officially withdrew from the Chinese agricultural market on June 15, 2018. According to China's policy, Streptomycin has been completely banned from production and use in agriculture. The United States has gradually reduced the use of methyl bromide since 2005. According to the Montreal Protocol, the United States nearly banned the use of methyl bromide in 2013.

Chemical fungicides play an important role in agricultural production, and the complete ban of chemical fungicides will cause huge losses in agricultural production. Under the current situation of rapid green development of the global plant protection industry, it is urgent to change the disease control strategy. As early as 2015, the Ministry of Agriculture of China launched the "Action Plan for Realizing Zero Growth in Pesticide Use by 2020", and completed the goal ahead of schedule in 2017. Compared with the traditional chemical pesticides, botanical pesticides have the technical advantages of low toxicity, less resistance, and less pollution. As the largest agricultural country in the world, China must consider the sustainability of future agricultural development and actively promote the research and development of green methods for plant disease prevention and control to reduce the use of chemical pesticides. This provides a good opportunity and huge space for the development of botanical pesticides.

Under the new situation and new requirements of global crop protection, Chengdu Newsun Crop Science Co., Ltd. (hereinafter referred to as "Chengdu Newsun"), based on the new ideas of "scientific dosage, alternation and chemical reduction, synergistic effect" , and the support of the existing research data, explored and integrated a core application technique with "botanical pesticide + chemical pesticide" to achieve chemical reduction and efficiency increase. Under the premise of improving the control efficacy, this technique reduces chemical resistance in plants, ensuring the duration of the efficacy, and reducing environmental pollution and pesticide residues.

2. Research status of garlic bulb extract

Garlic is the bulb part of the Allium plant in the Liliaceae family. As a medicine and food homologous plant, it is rich in nutrients and essential amino acids and is widely consumed by human. Garlic is a selenium-rich agricultural product. It has the functions of sterilizing and antibacterial, anti-cancer and anti-mutation, increasing biological activity, reducing cardiovascular and cerebrovascular diseases, and regulating the body's immunity. It is known as "natural antibiotic". Its medicinal value mainly lies in its sulfur containing compounds, the most important active ingredient allicin.

Fig. 1 Medicinal part of garlics

Since Pasteur clearly proposed that garlic has certain antibacterial activities in the 19th century, researches in this area have attracted the interest of many scholars, and garlic is therefore known as "plant-based natural broad-spectrum antibiotic". Cysteine is an essential molecule for bacterial reproduction and growth, and the oxygen atom contained in allicin can combine with the sulfhydryl group to inhibit bacterial growth . Allicin has a certain inhibitory effect on some pathogens, mainly against bacteria. It can be used to prevent diseases caused by bacterial pathogens in citrus, kiwi fruit, melons, solanaceous vegetables, leafy vegetables and other crops, such as angular spot, soft rot, canker, bacterial wilt, and etc. .

According to the report of Agropages, Chengdu Newsun has launched Allicin 5% ME formulation, a botanical bactericide, which has been registered in China and was launched on September 18, 2016. It can prevent bacterial diseases such as cabbage soft rot and cucumber bacterial angular spot, and prevent fungal diseases such as pepper wilt and Chuanxiong root rot, and achieve good disease resistance management.

Fig.2 Registration information of Allicin in ICAMA

Through the research and development concept of co-extraction technology and active molecular group of natural products, purify and separate the active ingredients in medicinal plant raw materials in different stages, significantly improve the utilization rate of  medicinal plant raw materials, reduce production costs, and significantly increase market competitiveness.

Fig.3 Allicin 5% ME contains various active ingredients

The nanometer level of the pesticide formulation produced by emulsification technology increases the adhesion and coverage of the active ingredients to the plant leaves and pathogens. Add high molecular surfactant to reduce the dynamic surface tension of the spray liquid, reduce droplet bouncing, improve speading and retention, greatly improve the utilization rate, and the efficacy of botanical pesticides in the fields.

Fig.4 Dynamic surface tension test of Allicin 5% ME formulation (1000 times dilution)

The appearance of Allicin 5% ME formulation is a light yellow homogeneous liquid, which disperses in water automatically when it is mixed with water, and is completely and rapidly miscible with water. The pH of the mixed solution is neutral, and can be mixed with any other non-alkaline pesticides, and easy to use. Adding moisturizing component, the spray liquid can resist high temperature environment and reduce evaporation on the leaves. Use environmentally friendly solvents to develop water-based environmentally friendly formulation. The production process of Allicin 5% ME is safe and environmentally friendly, has no pollution to the environment, and safe for storage and transportation.

Fig.5 The storage stability of Allicin 5% ME under cold and heat environments

Chengdu Newsun Allicin 5% ME formulation has excellent compatibility and solubility. After tank mixing with the chemical bactericide, the efficacy and the leaf adhesion and retaintion ability of the chemical bactericide can be improved. It provides a solid technical foundation for the development of plant protection and control strategy of "botanical pesticide + chemical pesticide".

Fig.6 The mixing and compatibility of Allicin 0.5% ME with Kasugamycin 2% AS

3. The use of Kasugamycin in Agriculture

As a broad-spectrum antibacterial ingredient which is widely used in agricultural production, Kasugamycin is widely used in the prevention and treatment of respiratory, digestive tract and genitourinary tract infections in poultry, such as avian influenza, chicken viral cold, chicken diarrhea, chicken dysentery, etc. In addition, Kasugamycin can also be used for the treatment of pigs, cattle and other livestock and poultry. For the prevention of crop diseases, Kasugamycin can inhibit the growth and reproduction of some plant pathogenic bacteria in soil and on leaves through its antibacterial effect. At present, there are more than 100 Kasugamycin technical and formulations registered in China, targeting on various crops and diseases such as rice blast and bacterial angular leaf spot. However, as an antibiotic bactericidal ingredient, long-term use of Kasugamycin may still lead to disease resistance. Through the prevention and control strategy of Allicin + Kasugamycin, the advantages of the two ingredients can be well exerted maximumly and minimize the development of pathogenic bacteria resistance.

4. Research on safety of the combination of Allicin + Kasugamycin

Allicin is a botanical pesticide. It is the extract of garlic bulbs which is derived from plants and used in plants. It has very good compatibility with plants, is safe for non-target organisms, and more friendly to the environment.

In order to verify safety of the combination of Allicin + Kasugamycin, we designed the experiments and verified the results of different concentrations of the combination on citrus leaves, young shoots and fruits. After three times of application, the treatments of Allicin 5% ME and Kasugamycin 2% AS were safe to citrus leaves, sprouts and fruits.

Fig.7 Safety test of different concentrations of Allicin + Kasugamycin

A: Kasugamycin 2% AS 500 times dilution; B: Allicin 5% ME 500 times dilution; C: Kasugamycin 2% AS + Allicin 5% ME (600+1000 times dilution); D: Kasugamycin 2% AS + Allicin 5% ME (800+800 times dilution); E: Kasugamycin 2% AS + Allicin 5% ME (1000+600 times dilution); F: Water

5. Research on the application technique of Allicin + Kasugamycin

At the same time, the results of the field test on citrus canker showed that 21 days after the two applications, the average efficacy of the control kasugamycin 2% AS 500 times dilution was 50.82%. The average efficacy of Kasugamycin 2% AS 600 times dilution + Allicin 5% ME 1000 times dilution was 76.80%. The average efficacy of Kasugamycin 2% AS 800 times dilution + Allicin 5% ME 800 times dilution was 81.96%. The average efficacy of Kasugamycin 2% AS 1000 times dilution + Allicin 5% ME 600 times dilution was 78.44%. The syngergistic effect and control efficacy were remarkable, the dose of Kasugamycin 2% AS was reduced by more than 30%, and the control efficacy was increased by more than 20%.

Fig.8 Test results on citrus canker (21days after 2^nd application)

A: Kasugamycin 2% AS 500 times dilution; B: Allicin 5% ME 500 times dilution; C: Kasugamycin 2% AS + Allicin 5% ME (600+1000 times dilution); D: Kasugamycin 2% AS + Allicin 5% ME (800+800 times dilution); E: Kasugamycin 2% AS + Allicin 5% ME (1000+600 times dilution); F: Water

Table.1 The field test result of Allicin 5% ME on citrus canker (21days after 2^nd application)

The field test results on eggplant wilt showed that after 8 days of root drench, the average control efficacy of Kasugamycin 2% AS 800 times dilution + Allicin 5% ME 800 times dilution on bacterial wilt could reach 92.05%, and the treated plants had normal fruit set and good growth condition.

Fig.9 The field result on eggplant bacterial wilt at 8 days after treatment
(Left: control; Right: Kasugamycin 2% AS + Allicin 5% ME) 

The field test results on mango bacterial angular leaf spot showed that after 7 days of last treatment, the average control efficacy of Kasugamycin 2% AS 800 times dilution + Allicin 5% ME 800 times dilution could reach 89.46%, and the control effect was remarkable.

Fig.10 The field result on mango bacterial angular leaf spot at 7 days after treatment
(Left: control; Right: Kasugamycin 2% AS + Allicin 5% ME)

The test results which were analyzed by Duncan's new atrophy in difference method showed that there was no significant difference in the prevention and control effect between Allicin 5% ME and Kasugamycin 2% AS which means Allicin 5% ME could have same control effect as Kasugamycin 2% AS. Moreover, the difference between the signal product group and the combination group in prevention and control effect reached a significant level. The efficacy of Kasugamycin 2% AS was significantly improved after tank mixing with Allicin 5% ME, and the prevention and control efficacy was the most significant when the both products were used at 800 times dilution.

6. The industrial development potential of the medicinal plant garlic

China is the world's largest country in garlic cultivation, and many regions have a tradition of growing garlic. China currently has two main garlic producing areas in the north and south. In 2017, China's garlic planting area and yield accounted for 51.98% and 78.88% of the world's total, respectively. At present, China is the largest garlic exporter in the world, and the export volume of garlic from 2014 to 2019 has generally shown an upward trend. According to the statistics of the Food and Agriculture Organization of the United Nations, from 2014 to 2017, China's garlic production, export volume and export value have increased steadily. In 2016, garlic export was 1,452,000 tons (81% of the world) and the export value reached $2.06 billion (90% of the world). These data show that China's garlic exports and export value rank first in the world. The complete garlic industry chain provides sufficient raw material supply for garlic-based botanical pesticides production, contributing strong support to the development of green agriculture.

7. Allicin + Kasuramycin: new strategy for green prevention and control of bacterial diseases under the trend of "Dual reduction in chemical fertilizers and chemical pesticides"

The combination of Allicin and Kasuramycin for bacterial disease control has better efficacy than Kasuramycin alone, and the two active ingredients from different sources act on different targets at the same time, and the mechanism of actions are complementary to each other, showing excellent synergistic effect, which provides a strong guarantee for the goal of reducing the dose of chemical pesticides and increasing efficiency. At the same time, the combination of Allicin and Kasuramycin can significantly reduce the application concentration of Kasuramycin, reduce the overuse and residue caused by Kasuramycin, and help the growers to deal with the problems and difficulties in prevention and control of plant bacterial diseases more scientifically. The combination of Allicin and Kasuramycin application technology reduces the environmental safety risks caused by excessive use of chemical bactericides, further improves crop quality, and brings greater value enhancement to agricultural products.

At present, bacterial diseases occur in many parts of the world all year round, which seriously restricts the economic development of various crops such as field crops, fruit trees, vegetables, grain and oil crops, and medicinal plants, and its market size exceeds 10 billion RMB. China's bacterial diseases currently occur in an area of 8 million hectares. According to incomplete statistics, there are about 200 kinds of crop bacterial diseases in China, and 60-70 kinds are common bacterial diseases, such as canker and wilt on solanaceae plants, bacterial angular leaf spot on melons, bacterial gummosis, citrus canker and etc. In recent years, with global warming and frequent extreme weather, the occurrence area of bacterial diseases on melons, vegetables and fruit trees is increasing at an annual rate of 10%, resulting in a 20%-30% reduction in crop yield. Therefore, the use of Allicin + Kasuramycin to prevent and control bacterial diseases has great market potential.

In future, through biopesticides + chemical pesticides, it will reduce the use of chemical pesticides, decrease the dependence of crop production on chemical pesticides, ensure crop safety and yield, reduce chemical pesticide residues and improve fruit quality, which has great industrial value and is an important way to promote the green development and sustainable development of agriculture.

Newsun Crop Science's website: http://www.cdxzy.com
E-mail: newsunagro@cdxzy.com