New approaches of treating chalk brood

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The fact that chalk brood is the most dangerous bee disease is out of doubt. The tendency of bees to become infected by this disease is great. For the last ten years chalk brood is noticed everywhere. Many researches of this problem (Grobov, Solovieva, 1998; Klotchko, 1999 and others) wrote about the reasons of the spreading or chalk brood. They are: general deterioration of bees resistance to diseases in connection of ecological pollution, breaking the rules of managing and breeding, using low effective therapeutic preparation that leads to the appearance of resistant cultures of Ascosphaera apis. Using one and the same preparation for treating chalk brood leads to appearing resistant cultures as well and gives only temporary improvement. The concentration of the pathogenic organisms reduces and the disease develops in the latent form, spores resistant to the preparation appear and give new forms of the pathogen, that propagating causes relapses of the disease in a more severe form. In order to avoid it the complex of sanitary-veterinary and curative measures should be taken on the apiary and also effective preparations should be alternated. In the last few years a wide variety of active fungicidal preparations was offered for treating chalk brood.

But as the practice have shown, all of them have some very significant drawbacks:

The peculiarities of disease pathogenesis are not taken into account. Preparations are spread all over the combs where there are died larvae. In order to have a therapeutic effect, the preparation must get into larvae's intestine together with honey and pollen.

The interval between treating the hive is too long 5-7 days, and if the concentration of fungicidal preparations is low, resistant cultures will appear.

Laboriousness of the works.

All these taken together made us work out a new, optimal preparation on the basis of raw materials of home manufacture.

The laboratory of vetenary sanitation of apiculture invented a new effective preparation for treating chalk brood- ASKOTAT. This antifungal preparation presents itself an oily concentrate of nystatin and in combintation of other active components. Its fungicidal effect against Ascosphaera apis has been studied in laboratory and on the apiaries. Its specific activity was determined in laboratory conditions according to the methods that had been worked out and modificated. Affected by Ascosphaera apis larvae were taken from the cells and put into sterile test-tubes as test-objects of the experiment. In 10-15 minutes native beer-wort agar (pH 7,0-7,2) was added in to the test-tubes and later 0,02 ml of the tested preparation in the concentration of 0,1; 0,01; 0,005; 0,001%. After incubating 3-5 days in thermostat at a temperature of 28-30C, the samples were examined. The diameter of the fungus colonies that appeared around the larvae was the criteria for fungicidal effect of the preparation. At the same time the activity of nystatin and other components of the preparation in the same concentration. In the control experiment larvae was not treated by the preparation. ( chart 1)

Thus, the obtained results prove the fact that askostat has a better fungicidal effect than nystatin. If the concentration of the preparation is 0,01 or 0,005% together with fungicidal effect, an active growth of microflora is observed that also hinders bacteria development. The data obtained in the laboratory were tested on the apiary .the experiments were held in spring and summer 1997,1998 before the season of main honey collecting.

Test and control groups were made after spring revision. The strength of the family, the amount of the brood in the cells, and the degree of chalk brood contamination.

The preparation askostat was put into honey-sugar candy which was fed to bees. Candy was prepared in two forms:

The first: 800 gr of sugar powder, 200 gr of honey, 10 ml of the preparation;

The second: 700 gr of sugar powder, 200 gr of honey, 100 gr of pollen, 10 ml of the preparation.

The mass was stirred and made in the form of cakes 500 gr each, put into plastic bags with slots 5 mm wide. The bags were put on the frames.

The first, second and third families were given curative candy (without pollen), the fourth, fifth, sixth- the candy prepared with pollen.

The control bee families got cakes without the preparation. Every three days the amount of eaten feed was calculated, the number of cured and ill larvae counted and the percentage of the brood affection in control and test bee families was determined. (see chart 2)

The results of the experiment showed that the preparation has a strong fungicidal effect.

Adding pollen to curative candy intensifies fungicidal effect. This is explained by the fact that bees use pollen for feeding young larvae (older than three days) and together with pollen the preparation gets into their intestine and prevents the development of fungus spores in their organism.

The preparation stays longer in the affected family if it is used with candy, and this definitely makes the preparation more effective and reduces the laboriousness of the curative measures.

The influence of askostat on the productivity of bee families, taking into account egg-laying efficiency of the queen, bees hygienic behavior was studied at the same time.

In order to learn the influence of askostat on the queen's egg-laying efficiency the amount of brood in the nest is counted. As the results showed the amount of brood increased from 26 up to 42%, that can be explained by therapeutic effect of askostat and stimulating influence of active components. In control group the amount of brood was constantly decreasing.

During the experiment affected larvae was removed by worker bees from the nest, adult bees, the queens or larvae died in none of the test group families.

In the course of experiment together with curative measures a number of sanitary-veterinary measures were also taken according to chapters 4.7.1-4.7.5 of The Instructions regulating desinfection, desacaristion, disinsectization, and deratization on apiaries of the Soviet Union, 25.06.1982

The toxicity of the preparation has been also investigated and the analysis has shown that it is nontoxic for bees and in recommended concentration it is not harmful to bee families.

In honey samples taken from experimental and control groups 7 and 14 days later there were no preparation residues found. The results obtained during experiment prove that bees use candy for feeding their feeding of larvae and themselves, but seal into combs. As curative measures with askostat are taken in early spring and summer ( when honey is not taken from hives for sale), the possibility if its presence in honey is minimal.

Askotat has been approved by Vetenary Pharmaceutical Biological council and allowed for usage on apiaries against chalk brood by Veterinary Department.

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English translation © Irina Yelsukova