JPH0224243B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to an agent for killing algae and fungi that parasitize the cells of seaweed (hereinafter referred to as laver) during cultivation. BACKGROUND ART Diseases that cause great damage in the cultivation process of seaweed include scab disease and pot fungus, and the pathogens thereof are algae fungi belonging to the genus Pythium and Olpidiopsis, respectively. Conventional countermeasures against red rot include drying out the leaves of nori plants in a net or storing them in a freezer at -20°C. Furthermore, the above-mentioned methods are ineffective for pot-shaped fungal disease, and no extermination method has been established. Additionally, malachite green and herbicide MCPB are being used in some areas. Problems to be Solved by the Invention Treatments such as drying out and freezing temporarily stop the growth of nori, and putting it in the freezer requires a great deal of labor and expense, and furthermore, it becomes impossible to cultivate the seaweed during this time. Chemicals such as malachite green and herbicides are highly toxic and persistent, so if they are treated incorrectly, there is a risk that the nori will die, and the chemicals will remain on the nori and may even get mixed into the dried nori of the product. There are drawbacks that can affect human health. Therefore, there is a strong demand in the art for a fungi-killing agent that does not have the above-mentioned problems. Means for Solving the Problems As a result of intensive research, the present inventor has found that gluconic acid solution is the causative agent of red rot and pot fungus, respectively.
It has been found that it has an excellent effect of killing or inhibiting the growth of algae and fungi of the genus Pythium and Olpidiopsis. The present invention provides a fungi-killing agent containing gluconic acid as an active ingredient. The pesticide of the invention consists of a solution of gluconic acid. When using the pesticidal agent of the present invention, the net on which the diseased seaweed is attached is dipped in the pesticide, or
Alternatively, spray the pesticide onto the nori on the net using a sprayer or a roller. In this way, by bringing the chemical solution into contact with the diseased cells of the nori, the parasitic algae and fungi are exterminated and the spread of the disease is prevented. The gluconic acid used in the pesticidal agent of the present invention may be either a solid called glucono delta lactone or a liquid in the form of gluconic acid. The solvent is usually water, most conveniently seawater. The glucono delta lactone dissolves in water and becomes gluconic acid. The concentration of gluconic acid in the pesticide of the invention is related to the contact time and is not critical. However, in both cases of dipping and spreading, the amount is preferably 0.5 to 20% by weight, most preferably 1 to 20% by weight. The contact time becomes shorter as the concentration increases and becomes longer as the concentration decreases. In the case of immersion, the net with glue attached to it is immersed in a chemical solution for a predetermined period of time, and then immediately pulled up and thrown into the sea to wash away the chemical solution adhering to the net. In the case of spraying, the seaweed is taken out of the sea with a net and sprayed, and the contact time is adjusted by putting it back into the sea after a predetermined time has elapsed after the spraying, or by washing it with water. If the concentration of gluconic acid is too low, the contact time will be too long to be practical.
Furthermore, if the concentration of gluconic acid is too high and exceeds 20% by weight, there is a risk of chemical damage unless the contact time is shortened, and too short a contact time will actually make the work more difficult. The pesticidal agent of the present invention may optionally contain an auxiliary agent. Examples of adjuvants include nitrogen, phosphoric acid, amino acids, etc. as nutrients for seaweed, organic acids such as citric acid and malic acid, and inorganic acids such as hydrochloric acid and nitric acid as acidic agents. The effectiveness of the pesticide of the present invention is illustrated by the following examples. The algae-parasitic nori used in the present Examples and Comparative Examples are as follows: A: A nori thallus that is infected with red rot and has a lesion about 5 mm in diameter due to spread of hyphae. Leaf length average 10cm. and B. Nori fronds affected by urn fungus disease, in which 10 or more urn fungus-infested cells are observed in one field of view under a microscope at 600x. Leaf length average 10cm. In each example, 10 sheets each of the above A and B were added to 200% of the pesticide seawater solution of each concentration shown in Table 1.
ml for the indicated contact time followed by washing with seawater. The nori leaves treated with the pesticide were placed in a 500 ml flask with a ventilation tube, and 500 ml of sterile seawater (sea water heated to 70°C and then cooled) was added to the mixture, which was free from both red rot and pot fungus. One piece of an intact, healthy nori leaflet (leaf length 20 cm) was divided into eight equal parts, and the healthy leaf piece was aerated and cultured for 7 days at a temperature of 10 to 15°C, and the degree of infection of the healthy leaf piece was examined. The degree of infection is determined by observing healthy leaf pieces under a microscope (600x magnification). In the case of red rot, dead cells have been penetrated by Pythium hyphae, and in the case of urn bacterium, cells infested with Olpidiopsis fungi are detected. The number seen in one field of view was investigated. This number was determined by surveying 10 visual fields and taking the average value. The effectiveness of the pesticidal agent of the present invention was evaluated based on the degree of infection. In Comparative Example 1, the same procedure as in Example was repeated, except that the above-mentioned algae and fungus parasitic laver A and B were not treated with a pesticide. In Comparative Example 2, the same procedure as in Example was repeated, except that the above-mentioned algae and fungus parasitic laver A and B were not treated with a repellent, and instead, they were dried in the sun for 2 hours. The results are shown in Table 1.

[Table] No infection was observed in the examples. It has a surprising effect compared to the infection degree of the comparative example. It is clear that the action of gluconic acid exterminates algal fungi and prevents them from infecting other nori.

Claims (1)

[Claims] 1. An agent that kills algae and fungi that parasitize the cells of laver, which contains gluconic acid as an active ingredient.