FUNGICIDAL EFFECT OF CYCLIC PEROXIDES ON THE GROWTH OF THE ENTOMOPATHOGENIC FUNGUS ASCOSPHAERA APIS

Abstract

In recent years, the number of pollinating insects in the world has decreased significantly. A possible reason for this is the toxic effect of agrochemicals, which reduces the immunity of insects, which leads to their increased sensitivity to pathogens. Ascosphaera apis is a dangerous entomopathogenic fungus that affects both honeybees and bumblebees. Ascosphaera apis causes the disease popularly known as "chalk brood" in bees and threatens beekeeping all over the world. All the identified species of fungi belonging to the genus Ascosphaera (Ascomycota: Plectomycetes, Ascosphaearales) were found when bees were affected. The fungus Ascosphaera apis (Maassen ex Claussen) is the etiological agent of invasive mycosis of honey bees called chalk brood. It is a heterothallic organism that forms spores when the mycelia of two different strains of the opposite sex touch each other and fruiting bodies are formed. The disease is transmitted through ingestion of spores from contaminated food by young bee larvae. After infection, the larvae quickly reduce their food intake until they stop eating altogether. Five-day-old bee larvae are most susceptible to the disease, as they have favorable conditions in the internal environment of the intestine for spore germination. Once in the gut of the larva, the spores are activated by CO2 obtained from the cells. They can then germinate into the lumen, forming a mycelium that pierces the cuticle of the larva. In this phase, the larvae look like tiny pieces of chalk or "mummies," which gives the chalk brood disease its name. As the disease progresses, the larvae mummify, changing color from white to dark gray or black due to the presence of spores on the larval cuticle. We investigated the fungicidal activity of cyclic peroxides based on atamar oxygen against A. apis isolated from the honey bee (A. mellifera). Peroxides showed a high inhibition of mycelial growth of A. apis up to 92–100% at a concentration of 10 ml/l. For the most active peroxides, the EC 50 value (half-maximum effective concentration) is determined. Two experimental peroxides showed higher antifungal activity against A. Apis than the commercial fungicide hydrogen peroxide 30%. The studied peroxides did not reduce the ability of bees to fly and did not lead to their death. A new field of application of peroxides in beekeeping has been opened.