Application of aescin in the preparation of feed repellents for fruit flies

Abstract

This invention discloses the application of aescin in the preparation of a feed repellent for fruit flies. This invention is the first to propose that the natural plant medicine aescin can be used as an insect feed repellent. Verification has shown that it has a significant feeding repellent effect on both adult and larval fruit flies, making it suitable as a feed repellent for fruit fly pests. Further development into a natural drug for controlling fruit fly pests is possible. It is non-toxic and pollution-free to various crops, vegetables, fruits, and other economic crops, will not induce drug resistance, and will not pollute the environment or harm human health, demonstrating excellent application prospects.

Description

Technical Field

[0001] This invention relates to the field of natural medicines and pesticides, specifically to the application of aescin in the preparation of a food repellent for fruit flies. Background Technology

[0002] Fruit flies are insects belonging to the family Tephritidae in the order Diptera. There are many species, and their larvae are all burrowing feeders, damaging various parts of plants, from roots, stems, leaves, flowers, and even fruits. Many species are crop pests, with those in the genus *Bactrocera* being particularly important. Fruit flies possess a stinger at the end of their abdomen, which serves as their ovipositor. The adult fruit fly lays its eggs inside the fruit, and the hatched larvae bore into the flesh, causing localized yellowing and eventually, complete rotting and foul odor, resulting in a large number of fruits falling off the plant. Even if the fruit doesn't rot, the puncture site oozes a resinous substance, causing deformities and sunken areas, hardened skin, and a bitter taste, severely impacting the quality and yield of the fruit. Several fruit fly species have been identified in China, including important pests of citrus, pear, and melon fruits and vegetables, such as the citrus fruit fly (*Bactrocera dorsalis*), the citrus fruit fly (*Bactrocera cirsalis*), the melon fruit fly (*Bactrocera melon*), and the wolfberry fruit fly (*Bactrocera goji berry*). Fruit flies have a very high reproductive capacity and are migratory, making chemical control ineffective.

[0003] The oriental fruit fly (Bactroceradosalis Hendel) is a major pest of citrus crops, widely distributed in tropical and subtropical regions worldwide, posing a particularly serious threat to the production of citrus and other fruit trees. Control techniques for the oriental fruit fly have made some progress in different regions, primarily employing integrated management methods such as chemical control and biological control.

[0004] Chemical control is a traditional method for controlling the citrus fruit fly, primarily involving the spraying of insecticides to control its population. Commonly used insecticides include organophosphates, pyrethroids, and systemic pesticides. However, due to the increasing resistance of the citrus fruit fly to certain pesticides, the effectiveness of single-method chemical control is decreasing, and chemical pesticides may have negative impacts on the environment and ecosystems. Therefore, over-reliance on chemical control is not recommended.

[0005] Biological control is a method of pest control that has gained increasing attention in recent years. It mainly involves using natural enemies of the oriental fruit fly to control its population. These natural enemies include parasitic wasps, predatory insects, and pathogenic microorganisms. Parasitic wasps can parasitize the eggs or larvae of the oriental fruit fly, achieving biological control. In addition, certain insect pathogens, such as fungi and viruses, are also used in biological control. Biological control is environmentally friendly and sustainable, and is gradually becoming a powerful supplement to chemical control.

[0006] In recent years, researching the regulatory effects of functional plants on insect behavior and developing insect behavior regulators has become an important research direction in the field of green pest control in agriculture. Utilizing plant-derived active ingredients to repel or inhibit pest behavior has gradually become an effective alternative to traditional chemical control, attracting increasing attention and application. For the control of the oriental fruit fly, researchers have begun to explore the potential of plant-derived substances, utilizing their natural repellent and inhibitory effects to reduce oriental fruit fly infestations. Specifically, plant extracts or their active ingredients, such as volatile essential oils and phenolic compounds, have been proven to effectively interfere with the phototaxis, chemotaxis, and oviposition behavior of the oriental fruit fly. These plant-derived substances can not only repel adult oriental fruit flies but also, to a certain extent, inhibit egg production and larval survival rates, thereby reducing the risk of pest outbreaks.

[0007] By screening plant-derived substances with high activity and low toxicity, researchers have developed a series of green control products, such as plant extracts and plant essential oil sprays, for the control of the oriental fruit fly. These products not only have good control effects but are also environmentally friendly, without negatively impacting other beneficial insects or the ecosystem. Therefore, plant-derived substances have broad application prospects in the control of the oriental fruit fly and will become an important component of future green agricultural control strategies.

[0008] The taste system is one of the key chemical sensing systems in insects. It plays a crucial role in sensing the chemical composition of food through direct contact and regulating behaviors such as mating, feeding, and oviposition. Among them, the insect Grs, which is involved in recognizing sweet and bitter substances (such as toxic plant metabolites), is very important for feeding decisions.

[0009] Insect repellents are specific agents that interfere with or inhibit the function of insects' taste receptors, preventing them from feeding. These chemicals generally prevent insects from feeding without directly killing them. Insect repellents not only protect plants from insect consumption but also contribute to the protection of ecological balance. Therefore, in plant protection work, insect repellents are an ideal potential insecticide, and their use in pest control can avoid and reduce the harm of chemical pesticides to the environment and humans.

[0010] Escin is a sodium saponin salt extracted from the dried, mature seeds of *Aesculus rotundus*, a plant in the Aesculaceae family. It is a freeze-dried, sterile preparation and a natural herbal medicine with anti-inflammatory, anti-swelling, analgesic, and blood circulation-improving effects. Currently, it is primarily used in pharmaceuticals. There are currently no reports on the use of escin to repel or prevent feeding on insects (such as the oriental fruit fly). Summary of the Invention

[0011] The purpose of this invention is to address the above-mentioned problems by providing an application of aescin in the preparation of a food repellent for fruit flies.

[0012] To achieve its objective, the present invention employs the following technical solution:

[0013] The first aspect of the present invention provides the application of aescin in insect antifeeding.

[0014] A second aspect of the invention provides the use of aescin in the preparation of insect antifeedants.

[0015] In the above-mentioned application technical solution, the insect is a fruit fly.

[0016] Preferably, the insect is a fruit fly (Bactrocera).

[0017] The fruit flies mentioned include the small citrus fruit fly, the large citrus fruit fly (Tetradacus citri (Chen)), the melon fruit fly (Bactroceracucuribitae (Coquillett)), the South Asian fruit fly (Bactroceratau Walker), and the Mediterranean fruit fly (Ceratitis capitata).

[0018] In the above-mentioned application technology, the working concentration of aescin is 0.1 μM or higher, preferably 0.1–1000 μM, 0.1–500 μM, 0.1–200 μM, 1.0–500 μM, or 1.0–100 μM.

[0019] A third aspect of the present invention provides an insect antifeedant, the active ingredient of which includes aescin.

[0020] The insect repellent is a fruit fly, preferably a fruit fly.

[0021] The insect predator also includes a solvent, wherein the solvent is selected from methanol or DMSO.

[0022] In the insect repellent, the concentration of aescin is 0.1 μM or higher, preferably 0.1–1000 μM.

[0023] The beneficial effects of this invention are: it is the first time that the natural plant medicine aescin has been proposed to be used as an insect repellent. It has been verified that it has a significant repellent effect on both adult and larval fruit flies, and can be used as a repellent for fruit fly pests. It can be further developed into a natural drug for the control of fruit fly pests. It is non-toxic and pollution-free to various crops, vegetables, fruits and other economic crops, will not produce drug resistance to chemical drugs, and will not pollute the environment or harm human health, and has a very good application prospect. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the experimental setup and method for the feeding selection of adult oriental fruit flies.

[0025] Figure 2 This is a schematic diagram of the experimental setup and method for the feeding selection of oriental fruit fly larvae.

[0026] Figure 3 This is the result of an experiment on the bidirectional selection behavior of adult oriental fruit flies in feeding.

[0027] Figure 4 This is the result of an experiment on the bidirectional selection behavior of citrus fruit fly larvae in feeding. Detailed Implementation

[0028] The present invention will be further described below with reference to embodiments, but these embodiments are not intended to limit the scope of the invention.

[0029] Unless otherwise specified, the experimental methods described in the following examples are conventional methods.

[0030] Example 1: Feed Selection Test

[0031] 1. Materials and Methods

[0032] The experimental insects were oriental fruit flies that had been cultured in our laboratory for a long time. The laboratory conditions were 27±1℃, 70%±5% relative humidity, and a photoperiod of 14:10 (light:dark).

[0033] The aescin used in this experiment (CAS No.: 6805-41-0) was purchased from Shanghai Yuanye Biotechnology Co., Ltd. Methanol was used as the solvent to dissolve and prepare solutions with concentrations of 1μM, 10μM, 100μM, and 1000μM for the experiment.

[0034] 1.1 Adult feeding preferences

[0035] The adult feeding selection experiment was conducted in transparent acrylic cages (25 cm × 25 cm × 25 cm). Two 3 cm diameter petri dishes were placed diagonally inside each cage. Each petri dish contained 10 ml of a 100 mM sucrose solution, and an aescin solution was added to the lower petri dish (multiple treatment groups with different concentrations of aescin solution were set up, with one acrylic cage representing one treatment). That is, the upper petri dish contained 100 mM sucrose solution, and the lower petri dish contained 100 mM sucrose solution + aescin. Multiple treatment groups with different concentrations of aescin solution were set up, with final concentrations of aescin in the feed solution of 0.1 μM, 1 μM, 10 μM, and 100 μM.

[0036] The experimental design included 30 oriental fruit flies in each treatment group, with three replicates per treatment to ensure statistical validity. Before the experiment, the oriental fruit flies were starved for 18 hours, then placed in acrylic cages and allowed to feed for 30 minutes. The number of oriental fruit flies in each petri dish was then counted. The feeding preference index (PI) was calculated using the formula shown in Formula I.

[0037] PI = (N 上侧 -N 下侧 ) / (N 上侧 +N 下侧 Formula I

[0038] In Formula I, N 上侧 N represents the number of oriental fruit flies in the upper petri dish. 下侧 This represents the number of oriental fruit flies in the lower petri dish.

[0039] 1.2 Larval feeding preferences

[0040] The larval feeding selection experiment was conducted using a bisection dish with a diameter of 9 cm. Feed was added to both sides of the dish. The feed on the left side of the dish consisted of artificial larval feed + sucrose (final concentration in the feed: 100 mM), while the feed on the right side consisted of artificial larval feed + sucrose (final concentration in the feed: 100 mM) + aescin (set at different final concentrations: 0.1 μM, 1 μM, 10 μM, and 100 μM). The artificial larval feed formula was as follows: 18 g agar, 30 g filter paper, 60 g white sugar, 60 g yeast, 75 g wheat germ powder, 180 g corn flour, 4.2 g methylparaben, 2.1 g sorbic acid, 3 g vitamin C, and 1 ml linoleic acid, diluted to 1 L with water to form a paste.

[0041] Thirty third-instar larvae were placed in the center of each dish and incubated in a dark, constant-temperature incubator at 25°C for 30 minutes to allow them to feed. The number of larvae on each side of the dish was then counted. Each treatment was performed in triplicate. The feeding preference index (PI) was calculated using Formula II.

[0042] PI = (N 左侧 -N 右侧 ) / (N 左侧 +N 右侧 )Formula II

[0043] In formula II, N 左侧 N represents the number of oriental fruit flies on the left side of the plate. 右侧 This represents the number of oriental fruit flies on the right side of the plate.

[0044] 2 Results and Analysis

[0045] 2.1 Adult insect feeding preferences

[0046] In the behavioral selection experiment, without the addition of aescin, the oriental fruit fly did not show any obvious preference or avoidance behavior in its feeding behavior. Figure 3 However, in the dual-selection feeding experiment of adults, after the addition of aescin, when the initial concentration of aescin was 0.1 μM, the oriental fruit fly quickly showed a clear preference for feeding in the upper petri dish without aescin, and as the concentration of aescin in the lower petri dish increased, the oriental fruit fly's aversion to aescin gradually increased. Figure 3 The preference index (PI) reached a peak of 0.596 at a concentration of 100 μM for aescin. The PI results are shown in Table 1.

[0047] Table 1. Adult insect double-selection experiment preference index (PI)

[0048]

[0049] 2.2 Larval feeding preferences

[0050] Unlike adults, larvae of the oriental fruit fly did not show a significant preference for aescin at a concentration of 0.1 μM. However, when the aescin concentration increased to approximately 1 μM, the larvae began to avoid feeding, reaching a peak preference index of 0.755 at a concentration of 100 μM. Figure 4 The Preference Index (PI) results are shown in Table 2:

[0051] Table 2. Larval Two-Choice Experiment Preference Index (PI)

[0052]

[0053] The above results indicate that aescin has a significant antifeedant effect on both adult and larval fruit flies of the citrus orientalis, and this effect is dose-dependent.

Claims

1. Use of escin in the feeding deterrence of Bactrocera dorsalis, the working concentration of escin being 0.1 μM or above.

2. Use of escin in the preparation of a feeding deterrent for Bactrocera dorsalis, the working concentration of escin in the feeding deterrent being 0.1 μM or above.

3. Use according to claim 1 or 2, characterized in that: The working concentration of escin is 0.1-1000 μM.

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