Serratia marcescens and application of serratia marcescens in prevention and treatment of fall webworms

Abstract

The invention is applicable to the field of microbial pesticides, and provides serratia marcescens and application thereof in prevention and treatment of fall webworm, the serratia marcescens is YZNUH-02, and the preservation number is CGMCC No.36002. The serratia marcescens YZNUH-02 strain provided by the invention is separated from naturally infected fall webworm larvae, and the serratia marcescens YZNUH-02 strain can be applied to prevention and treatment of fall webworm. The composition has strong pathogenicity on hyphantria cunea larvae, has high insecticidal efficiency, takes effect more quickly compared with the existing biological control means, and can quickly control the population quantity of hyphantria cunea. The strain and the related biopesticide belong to microbial source preparations, are green and environment-friendly, cannot cause environmental pollution after being used, cannot cause drug resistance of pests, and accord with the sustainable prevention and control concept.

Description

Technical Field

[0001] This invention belongs to the field of microbial pesticides, and in particular relates to a type of Serratia marcescens and its application in the control of the fall webworm. Background Technology

[0002] The fall webworm (Russula versicolor) is a significant quarantine pest in my country's forestry and landscaping sectors. Characterized by its high reproductive rate and rapid spread, it primarily damages various broadleaf plants, causing severe impacts on the ecological environment. Currently, control of the fall webworm still relies mainly on chemical pesticides. However, long-term use of chemical pesticides has led to significant resistance in the fall webworm, while also causing a series of problems such as environmental pollution and disruption of ecological balance, which does not meet the development needs of green pest control.

[0003] Existing biological control methods mainly include Bt agents, viral agents, and the release of natural enemy insects, but they have significant drawbacks: Bt agents and viral agents have a narrow pathogenic spectrum and are only effective against specific groups of pests; the control effect of natural enemy insects is greatly affected by environmental conditions and is slow to take effect, making it difficult to quickly control the population of fall webworm.

[0004] Serratia marcescens is a Gram-negative bacillus widely found in the environment. Some strains are pathogenic to insects, classifying it as a broad-spectrum insect pathogen with potential control potential against various lepidopteran pests. However, to date, the application of Serratia marcescens in the control of the American white moth has not been fully developed. There is a lack of targeted, highly pathogenic strains and supporting control technologies, failing to meet the actual needs for green and efficient control of the American white moth. Summary of the Invention

[0005] The purpose of this invention is to provide Serratia marcescens and its application in the control of American white moth, in order to solve the problems existing in the background art.

[0006] The present invention is achieved as follows: a *Serratia marcescens* strain, YZNUH-02, with accession number CGMCC No. 36002, was deposited at the China General Microbiological Culture Collection Center on September 22, 2025.

[0007] Another objective of this invention is to provide an application of Serratia marcescens in the control of the fall webworm.

[0008] Preferably, it includes the following steps: Add 25 mL of NA liquid culture medium to a sterile centrifuge tube; Use a sterile inoculation loop to pick up a colony of Serratia marcescens and inoculate it into NA liquid medium; The bacterial suspension was obtained by continuous incubation at 25℃ and 200 rpm / min for 24 hours. Biological pesticides are prepared from bacterial suspensions.

[0009] Preferably, the NA liquid culture medium consists of: 10.0g peptone, 3.0g beef extract, 5.0g sodium chloride, and distilled water to a final volume of 1L, with a pH of 7.0.

[0010] Preferably, the bacterial suspension is obtained by continuous culturing at 25°C and 200 rpm / min for 24 hours, and the concentration of the bacterial suspension is adjusted to 1×10⁻⁶ after continuous culturing. 4 ~1×10 8 cfu / mL.

[0011] Another objective of this invention is to provide a biological pesticide for controlling the fall webworm, the biological pesticide comprising the *Serratia marcescens* and its culture.

[0012] The present invention provides a strain of Serratia marcescens and its application in the control of the fall webworm, which has the following beneficial effects: The *Serratia marcescens* strain YZNUH-02 provided by this invention was isolated from naturally infected fall webworm larvae. It is highly pathogenic to fall webworm larvae, has high insecticidal efficiency, and is faster-acting than existing biological control methods, enabling rapid control of fall webworm populations.

[0013] This strain and related biopesticides are microbial-derived preparations, which are green and environmentally friendly. Their use will not cause environmental pollution or lead to pesticide resistance in pests, aligning with the concept of sustainable pest control. This expands the application areas of *Serratia marcescens*, fills the gap in dedicated *Serratia marcescens* biological control resources for the fall webworm, provides a new technological option for fall webworm control, and effectively compensates for the shortcomings of traditional chemical pesticides and existing biological control methods. Attached Figure Description

[0014] Figure 1 The frontal morphology of Serratia marcescens colonies on culture medium; Figure 2 The image shows the reverse side morphology of Serratia marcescens colonies on a culture medium.

[0015] Figure 3 This is a phylogenetic tree. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0017] The specific implementation of the present invention will be described in detail below with reference to specific embodiments.

[0018] Example 1: Isolation and Purification of Strains Collecting naturally infected fall webworm larvae requires all procedures to be performed in a sterile environment. The specific steps are as follows: 1) Disinfect the surface of diseased fall webworm larvae with 75% ethanol; 2) Rinse three times in sterile water to ensure that the ethanol remaining on the surface of the diseased insects is removed, and then air dry. 3) Place the insects that have undergone surface disinfection into a 1.5mL sterile centrifuge tube, add 0.5mL sterile water, and grind the insect tissue with a grinding rod until it is completely broken to form a bacterial suspension; 4) Dip a sterile inoculation loop into the bacterial suspension and streak it onto an NA solid medium plate. Incubate at 25°C for 24-48 hours. The NA solid medium consists of 10.0g peptone, 3.0g beef extract, 5.0g sodium chloride, 15.0g agar, and distilled water to a final volume of 1L. Adjust the pH to 7.0.

[0019] 5) Select a single colony for purification culture to finally obtain a single colony of Serratia marcescens YZNUH-02.

[0020] Example 2: Strain Identification Colony morphology: Serratia marcescens morphology as follows Figure 1 and Figure 2 As shown, the colonies are round, red, raised, opaque in the center, and have irregular edges.

[0021] Strain identification: The colonies were amplified and sequenced using universal primers for 16S rDNA. The sequencing results were compared and analyzed in the NCBI database, and the strain was finally identified as Serratia marcescens.

[0022] Phylogenetic trees constructed using MEGAX software, such as Figure 3 As shown.

[0023] Strain preservation: The strain was deposited on September 22, 2025 at the China General Microbiological Culture Collection Center (CGMCC), located at No. 1, Beichen West Road, Chaoyang District, Beijing, with accession number CGMCCNo.36002.

[0024] Example 3: Preparation of bacterial suspension All procedures must be performed in a sterile environment. The specific steps are as follows: 1) Add 25 mL of NA liquid culture medium to a sterile centrifuge tube for later use; 2) Use a sterile inoculation loop to take a small amount of Serratia marcescens YZNUH-02 colony and inoculate it into the above NA liquid culture medium; 3) Incubate continuously at 25℃ and 200 rpm / min for 24 h, with NA liquid medium as the control; 4) After cultivation, adjust the bacterial suspension concentration to 1.0 × 10⁻⁶. 8 CFU / mL. The NA liquid culture medium consists of 10.0g peptone, 3.0g beef extract, 5.0g sodium chloride, and distilled water to a final volume of 1L, with the pH adjusted to 7.0.

[0025] Example 4: Insecticidal Activity Assay Preparation of bacterial suspensions at different concentrations (1×10⁻⁶) 4 ~1×10 8 (cfu / mL) Different concentrations of bacterial suspension were used to soak artificial feed for the fall webworm, and then the soaked feed was used to feed the third instar larvae of the fall webworm. Larval mortality was continuously recorded, and Probit analysis was performed using SPSS 26 software to calculate LT. 50 The values ​​are shown in Table 1.

[0026] Table 1. LT of Serratia marcescens YZNUH-02 on 3rd instar larvae of the fall webworm. 50

[0027] Example 5: Verification of Koch's Law The bacterial strain was re-isolated from the dead American white moth larvae; The re-isolated strains were compared with the original Serratia marcescens YZNUH-02 in terms of morphology and molecular biology. Results: The re-isolated strain had the same characteristics as the original strain, confirming that *Serratia marcescens* YZNUH-02 was the pathogen causing the death of American white moth larvae.

[0028] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A type of Serratia marcescens, characterized in that, The *Serratia marcescens* strain described is YZNUH-02, with accession number CGMCC No.36002, and was deposited at the China General Microbiological Culture Collection Center on September 22, 2025.

2. The application of Serratia marcescens as described in claim 1 in the control of American white moth.

3. The application according to claim 2, characterized in that, Includes the following steps: Add 25 mL of NA liquid culture medium to a sterile centrifuge tube; Use a sterile inoculation loop to pick up a colony of Serratia marcescens YZNUH-02 and inoculate it into NA liquid medium; The bacterial suspension was obtained by continuous incubation at 25℃ and 200 rpm / min for 24-48 h. Biological pesticides are prepared from bacterial suspensions.

4. The application according to claim 3, characterized in that, The NA liquid culture medium consists of: 10.0g peptone, 3.0g beef extract, 5.0g sodium chloride, and distilled water to a final volume of 1L, with a pH of 7.

0.

5. The application according to claim 3, characterized in that, The bacterial suspension was obtained by continuous culturing at 25℃ and 200 rpm for 24-48 hours. After continuous culturing, the concentration of the bacterial suspension was adjusted to 1×10⁻⁶. 4 ~1×10 8 cfu / mL.

6. A biological pesticide for controlling the fall webworm, characterized in that, The biological pesticide comprises Serratia marcescens and its culture as described in claim 1.

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