JPS6140207B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a fish ectoparasiticide containing O,O-dimethyl O-(5-phenyl-3-isoxazolyl) phosphorothioate (hereinafter abbreviated as methylisoxathion) as an active ingredient. BACKGROUND ART When cultivating eels, carp, goldfish, etc., damage caused by fish ectoparasites is significant, and there is a demand for their precise extermination. Conventionally, O,O-dimethyl (1-hydroxy-2,2,2-trichloroethyl) phosphonate (hereinafter abbreviated as trichlorophon) has been used for this purpose, but its toxic concentration for fish and its effectiveness against parasites are limited. It has the disadvantage that it is dangerous to use because there is not much difference in concentration, and that it cannot exterminate the sessile callus insect. Methylisoxathion used in the present invention is described in Japanese Patent Publication No. 43-6716 as being effective against agricultural pests such as grasshoppers, planthoppers, leafhoppers, mites, and aphids on rice, field crops, and fruit trees, and sanitary pests such as flies and cockroaches. This compound is known as an insecticide, but the present inventors have discovered that it exhibits exceptional effects when used to exterminate parasites on the surface of fish. That is, the methyl isoxathion of the present invention is effective against blood-sucking parasites of fish, such as parasitic crustacean gill tail worms (commonly known as snails, snails, sea snails, etc.), sessile radial worms (calicum, salmincola, etc.), and sessile radial worms ( It is effective against body lice, Ergacillus, etc.) and solitary trematodes that parasitize the gills and skin (Digitatoris, tertiary worms, etc.). In addition, methylisoxathion not only has low toxicity to warm-blooded animals, but is also highly safe to seafood, and TLm is
If it is around 5ppm and 2.5ppm or less, it is completely safe. In addition, the rate of decomposition in water is characteristically extremely fast, which is a common serious drawback of organophosphorus agents, and can result in flaking and fractures of fish spines when overdosed.
The so-called back bending phenomenon does not occur either. In addition, it has excellent effects and does not have any negative effects on phytoplankton. In order to use methyl isoxathion for the purpose of the present invention, it is preferable to formulate it into an emulsion because methyl isoxathion is sparingly soluble in water. Emulsions are prepared in the same way as when used as agricultural chemicals, and 50% emulsions are commonly used. When used, it is common to use a chemical bath method in which a chemical solution is poured into a fish pond containing parasite-infested fish by a method such as spraying and maintained at a predetermined concentration. It is preferable to use a concentration of 0.5 ppm regardless of the type of parasite, and a concentration of 2.5 ppm or less is safe for fish. Next, a test example is shown. Test Example 1 Five adult Argulus japonicus, which adsorb or hang onto the body surface of a fish and suck blood with its proboscis, were attached to each fish, and these were placed in fresh water.
Each fish was placed in a beaker filled with 50% methyl isoxathion, and a serially diluted solution of 50% methyl isoxathion emulsion was added thereto. As a result, as shown in Table 1, at a water temperature of 25°C, methyl isoxathion has a concentration equivalent to the original substance.
At 0.1 ppm, the gill tail worms were annihilated within 2 hours, at 0.005 ppm within 18 hours, and at 0.001 ppm within 48 hours, and they were completely removed from the fish body.

[Table] Test Example 2 Green water with abundant phytoplankton collected from fresh water and a koi pond (dominated by Microcystis) was added at 10.0% each.
In a filled circular glass aquarium, gill tail beetles (A.
Ryuukin 2 with 5 attached (Japonicus)
Accommodate the tails and add 50% methyl isoxathion to these
Serial dilutions of the emulsion and trichlorfon (crystals) were added separately for comparison. The results are shown in Table 2. At a water temperature of 25°C, the minimum concentration of methylisoxathion that kills gill tail insects is 0.001 ppm in fresh water and 0.001 ppm in green water after 48 hours.
The concentration was 0.01ppm (hereinafter referred to as the original concentration), but in the case of trichlorfon, it was more than 0.1ppm in fresh water and more than 0.5ppm in green water, indicating that this product was more than 50 times more powerful than trichlorfon against gill tail insects. .

[Table] Test Example 3 The squid insect (Lernaea cyprinacea) burrows into the body surface or oral cavity of fish and becomes a fixed parasite. Therefore, we carefully extracted 10 female adults from carp.
The specimen was placed in a shear dish filled with 20 ml of clean water, to which a sample dilution solution was added stepwise and the progress was observed at 25°C. Under the transmitted light of a mercury lamp, individuals in which intestinal peristalsis ceased and the insect body became cloudy and opaque were determined to be dead. The results are shown in Table 3. Methylisoxathion was used at a concentration of 2.0 ppm after 24 hours.
At 1.0ppm, each was annihilated after 48 hours, and
Even at 0.5ppm, 7 out of 10 individuals died after 72 hours. On the other hand, even at 20 ppm, trichlorfon was only reduced by half after 72 hours, and was ineffective at 10 ppm.

【table】

[Table] Test Example 4 Two fish infested with 1-8 L. cyprinacea were released into fresh water at 10.0 ml, and a 50% emulsion of methyl isoxathion and a serially diluted solution of trichlorfone crystals were added, and the water was kept for 12 days. I followed the progress. The results are shown in Table 4. At a water temperature of 25°C, methyl isoxathion has a concentration equivalent to the original substance.
Within 4 days at 0.4ppm, within 6 days at 0.2ppm,
At 0.1 ppm, all the insects became cloudy and died within 8 days. On the other hand, trichlorfon is close to a toxic dose.
It was effective even at 10 ppm, with all insects surviving after 12 days.

[Table] Test Example 5 A 50% methyl isoxathion emulsion was used as a product in an eel farming pond (holding about 30,000 eels) where large numbers of squid insects (L. cyprinacea) were parasitic in the eel mouths, resulting in poor feeding. The drug was administered repeatedly three times every week at a concentration of 0.5 ppm (0.25 ppm in terms of the drug substance). As shown in Table 5, the estimated morbidity rate and average number of parasites decreased dramatically with each administration, and complete eradication was achieved after three eradications from the pond. During this time (water temperature 26.0 -
(33.5°C, PH7.3-10.9), food intake significantly improved immediately after the second withdrawal, and completely returned to normal two weeks after use.

[Table] Test Example 6 Solitary flukes that parasitize the gills of fish are generally highly lethal. There, hundreds or thousands of Dactylogyrus spp were parasitic on the gills on both sides, and two of each Ryukin were in a moribund state, such as surfacing inverted or rolling over on the bottom of the tank.
The tail was placed in a beaker filled with 500 ml of fresh water and serial dilutions of 50% methyl isoxathion emulsion and trichlorfone crystals were added. The water temperature was maintained at 25°C, and the gills of dead fish were removed at the time of death, and the gills of fish that had survived after 18 hours were removed and the number of surviving insects was counted. The results are shown in Table 6. In the gills of the drug-free group (control) that died after 3 and 6 hours, approximately 300 and 500 trematodes were infested only in the first gill on the left side, respectively. On the other hand, methyl isoxathion was found to have a fluke killing effect even at a concentration of 0.0125 ppm, and the total amount of fluke killing effect was observed in all gills of surviving fish examined after 24 hours.
Only 154 surviving insects were counted. on the other hand,
In the case of trichlorfon, a total of 430 bodies remained in the surviving fish treated with 0.1 ppm even after 24 hours, indicating that it was far less effective than methylisoxathion.

[Table] Test Example 7 In order to maintain dissolved oxygen in the water and keep the eels in a resting state, it is necessary to have phytoplankton flourish, which is called "water creation." Therefore, since it would not be practical if the phytoplankton were to die when the methyl isoxathion preparation was removed from the eel pond, the effect on this was investigated. Green water collected from an eel pond (containing Chlorella, Ikadamo, Muremikazukimo, and Itokuzumo) is filtered to remove zooplankton, and then diluted with Mitskel's medium and added with 50% methyl isoxathion.
Serial dilutions of % emulsion were added. This was cultured in a constant temperature room at 25℃ for 5 days under continuous electric light.
Measure the light transmittance (maximum absorption) using a photoelectric colorimeter.
575nm) was measured. The results are shown in Table 7. At 10 ppm or more of this product, all green algae were wiped out after 5 days, at 5 ppm the growth was slightly inhibited, but at 1 ppm or less it was completely harmless. Rather, the average transmittance of the control (58.0%)
Compared to this, 0.05ppm of this product is 49.0%,
This suggests that phosphorus is used as a nutrient source for green algae.

【table】

[Table] As is clear from the above test examples, methylisoxathion is far more effective at killing insects than torchlorfone, which has been widely used in fish farms. In particular, it has a great advantage in that it can exterminate the sessile sessile beetle, which was almost impossible to control with conventional products.

Claims (1)

[Claims] 1 O,O-dimethyl O-(5-phenyl-3-
A fish ectoparasiticide containing phosphorothioate (isoxazolyl) as an active ingredient.