SU390727A1 - - Google Patents

Description

METHOD OF OBTAINING MICROBIAL INSECTICIDE

The invention relates to the field of protection of cultivated plants from insect-1 pests by microbiological means, and more specifically to microbiological methods for the production of insecticidal substances.

A method of obtaining microbiological preparations containing microorganisms belonging to the species Bacillus thuringiensis is already known for controlling harmful insects of the garden, vegetable garden and forest, based on the fact that protein crystals-toxins formed in the spore cells of these microorganisms exhibit a high toxicity to insect larvae. Gamma-endotoxins cause poisoning resulting in the death of insects.

Known drugs have a similar insecticidal effect on the silkworm. In addition, the action of the product continues even after spraying, as in the bodies of insects killed by toxins a secondary infection occurs due to the formation of spores, which is transferred to other individuals, in particular silkworm, wind, rain, animal and insect movement.

A method for producing a microbial insecticide is proposed, including the cultivation of

You. thuringiensis in a liquid nutrient medium, the release of snur and toxins by means of centrifuges and drying, in which, in order to eliminate secondary infection, spores are unable to reproduce, retaining their insecticidal activity. To this end, the culture fluid is treated during the period of minimal formation of toxins with hydrogen peroxide, p-propylactone or ultrasound.

During the period of minimal toxin formation, cultivation is interrupted and hydrogen peroxide is added to the culture fluid at a rate of 0.5-5.0 wt.%, P-propylactone is taken at a rate of 0.25 wt.%. The exposure to ultrasound is carried out at the rate of 20 kilocycles for 20 minutes.

Example. A microorganism belonging to the species you are. thuringiensis, are isolated from dead insects and cultured, and then the most toxic strains are selected.

10 ml of medium consisting of 1 ml of distilled water, 10 g of peptone, 10 g of meat extract and 3 g of sodium chloride are loaded into a test tube and the pH is adjusted to 7.2. After sterilization, the medium is inoculated with selected strains. Cultivate; Fovanpe is carried out with agitation for 72 hours. Spores and gamma toxins are harvested by centrifugation (15 ° C, 7000 rpm, 10 min) and washed with distilled water, then centrifuged again (5 ° C, 7000 rpm, 10 min) and dried in vacuum with retaining the ability their reproduction. The solids are diluted with water to a concentration of 2% by weight and, after stirring, sprayed onto the mulberry leaves, which feed twenty silkworms of the second day of the second age to determine the virulence of the strain. The results are given in table. 1. Table 1 Note. The total number of experimental insects of each strain is 20. From the data table. 1 shows that the strongest virulence strains are A, E, F. These strains are grown in sterile medium (500 ml at 27 ° C for 96 h) of composition, g / l: 5 KH2PO4, 5 K2HPO4, 0, 0002 hydrochloric thiamine, 0.5 M.gSO4, 0.3 MnSO4, 0.01 FeSOi, 0.05 CaCb, 1.5 Na -NHiPOi, 3 citrates of sodium and 10 Casamio acid. After confirming with a phase contrast microscope that the formation of Table 2 is formed - indicates destroyed, + indicates 60 survived. + the effectiveness of toxins is slightly reduced compared to untreated culture fluid; TOKCIIHOB's efficacy is the same as that of the untreated liquid. 65 sufficiently crystalline toxins are stopped, cultivation is stopped, and the culture fluid is processed to deplete the spores of reproduction. As a sample: 5% of the total agent, hydrogen lerexium is added at the rate of 0.065; 0.125; 0.25; 0.5; 0.75; 1.0; 2.0; 3.0; 5.0 wt.%. After 24 hours, take 1 ml of the treated culture fluid and inoculate 10 L1L sterile medium. The results are given in table. 2, from which it can be seen that, when 0.5% by weight is added to the culture liquid; % hydrogen peroxide alive spores were observed. Since after the addition of 0.5% or more of hydrogen peroxide, the surviving spores are not observed at all, each strain is treated with hydrogen peroxide at a rate of 0.5% by weight to make it impossible for the spores to multiply, the spores are harvested by centrifuging (5 ° C, 7000 rpm, 30 min) are washed several times with distilled water, dried under reduced pressure to obtain dry substances. Then a 2% preparation is prepared and evenly applied to the mulberry leaves, which are fed to four silkworms. The result confirms that the treated preparation can completely kill the silkworm in 2–3 hours and that the toxins in the cells are in an active state. The same results are obtained with preparations treated with p-propylactone taken at the rate of 0.25 wt.% Or with ultrasound at the rate of 20 kilocycles for 20 minutes. Experiments were carried out to determine the insecticidal activity of a preparation obtained from a strain (Table 1) as above, on harmful insects. The results are shown in Table. 3. Table 3 From table. 3, it can be seen that the microbial insecticide obtained by depriving the microorganism of its ability to multiply has an insecticidal effect on harmful insects. In addition, the microbial insecticide does not cause a secondary infection and therefore does not adversely affect the silkworm. These dry cells are introduced into the mice in doses of 3 3 per 1 kg of weight, and no poisoning or disturbance of physiological functions occurs. 5 Subject of the invention 1. A method for obtaining a microbial insecticide, including cultivating Bacillus thuringiensis in a liquid nutrient medium, eliminating spores and toxins by centrifuging and drying, characterized in that, in order to eliminate secondary infection, spores deprive the ability to reproduce, retain them insecticidal activity. 2. The method according to claim 1, characterized in that the deprivation of the spores of the possibility of reproduction is carried out by treating the culture with 39072,. b liquid peroxide hydrogen p-propylactone or ultrasound. 3. A method according to claim 2, characterized in that hydrogen peroxide is taken to process the culture fluid at the rate of introduction of 0.5-5.0% by weight. 4. The method of claim 2, wherein p-propylactone is taken at the rate of 0.25 weight.% For treating the culture liquid. 5. A method according to claim 2, characterized in that the treatment of the culture fluid with ultrasound is carried out at the rate of 20 kilocycles for 20 minutes.