A fungicidal composition for controlling brown spot of citrus

Abstract

The present application belongs to the technical field of lemon soot disease prevention and treatment, and particularly relates to a fungicidal composition for preventing and treating lemon soot disease. The fungicidal composition for preventing and treating lemon soot disease is composed of fluazinam and cnidim or composed of fluazinam and matrine; wherein, the synergistic mass ratio of fluazinam and cnidim is 1-8:20-1; the synergistic mass ratio of fluazinam and matrine is 1-7:9-1. The present application compounds fluazinam with other fungicidal active ingredients cnidim and matrine, which can improve the prevention and treatment effect on lemon soot disease compared with single component; at the same time, it can also reduce the resistance risk of single fungicidal component, which has important significance for developing fungicides for directly preventing and controlling lemon soot disease.

Description

Technical Field

[0001] This invention belongs to the field of lemon sooty mold control technology, specifically relating to a bactericidal composition for controlling lemon sooty mold. Background Technology

[0002] Sooty mold in lemons affects leaves, branches, and fruit. In the early stages, dark brown speckled mold spots appear on the surface of leaves, branches, and fruit, gradually expanding until a gray, dark brown, or black mold layer forms. Symptoms vary depending on the specific pathogen. *Citrus sooty mold* produces a thin, black, papery mold that is easily torn off and falls off naturally; *Citrus spicata* produces a sooty layer resembling the ash at the bottom of a pot, which flakes off in patches when rubbed, and is predominantly found on the leaf surface; *Citrus butlerii* produces a radial, black or dark brown mold patch that is scattered on both the upper and lower surfaces of the leaves, but does not cover the entire leaf or fruit.

[0003] Indirect control of lemon sooty mold can be achieved by controlling pests such as whiteflies, aphids, and scale insects, but this method is not very effective. Therefore, studying the indoor toxicity of fungicides against the pathogen of lemon sooty mold is of great significance for the control of lemon sooty mold.

[0004] Fluopyram is a key product in the new generation of succinate dehydrogenase inhibitors (SDHI) fungicides. Developed by Syngenta, it is a pyrazolamide fungicide that inhibits pathogen growth and ultimately kills pathogens by interfering with respiratory chain complex II, preventing energy synthesis. While fluopyram, as a new generation SDHI fungicide, has many advantages, long-term use as a single component will inevitably lead to the development and progression of drug resistance in pathogens, posing a risk of resistance development. Summary of the Invention

[0005] The purpose of this invention is to provide a bactericidal composition for the prevention and control of lemon sooty mold, which, compared with the single component fluopyram, can improve the control effect on lemon sooty mold and reduce the risk of drug resistance.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A bactericidal composition for preventing and controlling lemon sooty mold, wherein the bactericidal composition for preventing and controlling lemon sooty mold is composed of fluopyram and osthol, or of fluopyram and matrine; wherein the synergistic mass ratio of fluopyram to osthol is 1-8:20-1; and the synergistic mass ratio of fluopyram to matrine is 1-7:9-1.

[0008] For even better results, the synergistic mass ratio of fluopyram to osthol is 4:1.

[0009] For even better results, the synergistic mass ratio of fluopyram and matrine is 1:7.

[0010] A fungicide, wherein the fungicide is prepared by using the aforementioned fungicide composition for controlling lemon sooty mold as the active ingredient, supplemented with auxiliary ingredients permitted to be added in pesticide science.

[0011] In the bactericide, the bactericidal composition for controlling lemon sooty mold accounts for 1-90% of the total mass of the bactericide.

[0012] In this invention, the pesticide-grade auxiliary ingredients are selected from one or more of solvents, emulsifiers, dispersants, wetting agents, inert carriers, disintegrants, antifreeze agents, thickeners, preservatives, synergists, stabilizers, and deionized water.

[0013] The use of the bactericide in the prevention and control of lemon sooty mold.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] This invention combines fluopyram with other fungicidal active ingredients such as osthol and matrine, which can improve the control effect against lemon sooty mold compared with single ingredients; at the same time, it can also reduce the risk of drug resistance of single fungicidal ingredients, which is of great significance for the development of fungicides that directly control lemon sooty mold. Detailed Implementation

[0016] The technical solution of this invention patent will be clearly and completely described below with reference to specific embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0017] Example Indoor toxicity experiments

[0018] The virulence of each single agent and its mixture was determined by the mycelial growth rate method using Capnodium citri Berk. et Desm, a strain of citrus sooty mold isolated and purified from lemon sooty mold samples.

[0019] 1. Test reagents

[0020] 98% fluopyram technical grade, 98.5% osthol technical grade, and 98% matrine technical grade. The technical grades were completely dissolved and prepared into a 5000 mg / L stock solution using 0.1% (v / v) of emulsifier Tween-80, and stored for later use.

[0021] 2. Single-dose toxicity assay

[0022] The test reagent was diluted with 0.1% (v / v) Tween-80 emulsifier to create five mass concentration gradients. Then, it was mixed with PSA medium (200g peeled potato, 20g sucrose, 17g agar, 1000mL sterile water) at a volume ratio of 1:9. The mixture was then poured into equal volumes of 10mL into 9cm diameter petri dishes to prepare the drug-containing medium.

[0023] Under aseptic conditions, the test strain was inoculated onto PSA plates and incubated at 28°C for 7 days. Afterward, 5mm diameter mycelial discs were punched from the edge of the colony and inoculated into the center of the drug-containing medium (mycelial side down, contacting the medium). One mycelial disc was inoculated per plate, with an equal volume of 0.1% Tween-80 emulsifier as a blank control. Five plates were treated with each concentration of drug solution, and after capping, they were incubated at 28°C for 5 days. The colony diameter was measured using the cross-sectional method, and the average value was taken to calculate the inhibition rate of mycelial growth for different agents. The toxicity regression equation for each single agent was calculated by plotting the logarithm of the drug treatment concentration (mg / L) on the x-axis and the corresponding inhibition rate probability on the y-axis, and the median inhibitory concentration (EC50) was calculated. 50 ).

[0024]

[0025] 3. Combined toxicity assay of mixed-dose formulations

[0026] Based on single-agent toxicity assays, multiple formulations were established and diluted with 0.1% (v / v) Tween-80 emulsifier to create five mass concentration gradients. Then, combined toxicity assays of the mixtures were conducted using the same method as single-agent toxicity assays, with an equal volume of 0.1% (v / v) Tween-80 emulsifier as a blank control. The inhibition rates of different formulations on mycelial growth were calculated. The toxicity regression equations for different formulations were derived by plotting the logarithm of the drug concentration (mg / L) on the x-axis and the corresponding inhibition rate probability on the y-axis, and the median inhibitory concentration (EC50) was calculated. 50 ).

[0027] 4. Data Analysis

[0028] The synergistic coefficient SR of the mixture was calculated using the Wadley method to evaluate the type of combined action of the mixture.

[0029] The synergistic effect of drug combination was evaluated based on the synergistic coefficient SR, i.e. SR < 0.5 indicates antagonistic effect, 0.5 ≤ SR ≤ 1.5 indicates additive effect, and SR > 1.5 indicates synergistic effect. The results are shown in Table 1-3.

[0030] Relative toxicity index TI = (Standard reagent EC) 50 / Test reagent EC 50 )×100

[0031]

[0032] Among them, X1 is the EC of the mixture. 50 Theoretical value, unit: mg / L; P A --Percentage content of A in the mixture, unit: %; P B --Percentage content of B in the mixture, unit: %; A--EC of A in the mixture 50 Value, unit: mg / L; B -- EC50 of B in the mixture 50 Value, unit: mg / L;

[0033]

[0034] Wherein, SR is the synergistic effect coefficient of the mixture; X1 is the EC value of the mixture. 50 Theoretical value, unit: mg / L; X2 -- EC of the mixture 50 Measured value, unit: mg / L.

[0035] Table 1. Results of virulence assays for single agents against *Citrus aurantium*.

[0036]

[0037] Table 2. Results of toxicity assays of fluopyram and osthol at different mass ratios against *Citrus sooty mold*.

[0038]

[0039] Table 3. Virulence test results of fluopyram and matrine at different mass ratios against *Citrus sooty mold*.

[0040]

[0041] As shown in Tables 1-3, when fluopyram, Cnidium monnieri, and matrine are combined in different mass ratios, the synergistic effect against *Corydalis citrinum*, the pathogen of lemon sooty mold, is greater than 1.5, demonstrating a combined synergistic effect. Compared with single-component formulations, this combination can improve the control efficacy against lemon sooty mold; at the same time, it can reduce the risk of drug resistance associated with single fungicides, which is of great significance for developing fungicides that directly control lemon sooty mold.

Claims

1. A bactericidal composition for preventing and controlling lemon sooty mold, characterized in that, The bactericidal composition for preventing lemon sooty mold is composed of fluopyram and osthol; wherein the synergistic mass ratio of fluopyram to osthol is 1-8:20-1.

2. The bactericidal composition for preventing and controlling lemon sooty mold according to claim 1, characterized in that, The synergistic mass ratio of fluopyram to osthol is 4:

1.

3. A bactericide, characterized in that, The fungicide is prepared using the fungicide composition for controlling lemon sooty mold as described in claim 1 as the active ingredient, supplemented with auxiliary ingredients permitted to be added in pesticide science; the auxiliary ingredients permitted to be added in pesticide science are selected from one or more of solvents, emulsifiers, dispersants, wetting agents, inert carriers, disintegrants, antifreeze agents, thickeners, preservatives, synergists, stabilizers and deionized water.

4. The bactericide according to claim 3, characterized in that, The mass of the bactericidal composition for preventing lemon sooty mold accounts for 1-90% of the total mass of the bactericide.

5. The use of the bactericide according to claim 3 in the prevention and control of lemon sooty mold, characterized in that, The pathogen causing lemon sooty mold is *Citrus sooty mold* (Citrus sooty mold). Capnodium citri Berk. et Desm).

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