Effect of preparations containing humic substances and pure humic acids on colony growth and spore germination of entomopathogenic fungi from the Beauveria genus

The experiment examined the effect of commercially available preparations containing humic substances in comparison with pure humic acids on the growth and germination of spores of entomopathogenic fungi (EPF) of the genus Beauveria in vitro. AmiAGRA, HumiAGRA, Algo-HUM (recommended field dose) and pure humic acids extracted from peat, brown coal and mushroom substrate were added to Sabouraud’s culture substrate. Observation of the growth of colonies of the tested of EPF was carried out every 5 days until day 20, measuring their diameter (mm). In the second stage of the experiment, the culture medium with the addition of preparations and pure humic acids was applied in a thin layer to the surface of glass slides and 0.1 ml of an aqueous solution with spores was introduced. Observation was carried out after 24 h and 48 h, and the results obtained were expressed as percentages of the control. The conducted research showed that on the 20th day of culture (on average), preparations containing humic substances had a sti-mulating effect, while pure acids slightly limited the growth of colonies of the tested species. The growth of the colony of the fungus B. basianna was most strongly stimulated by AmiAGRA, and B. brongniartii by HumiAGRA. The share of germinated spores of the tested species after 48 h of contact with the substrate was higher than after 24 h. It was found that more spores germinated on substrates with the addition of preparations containing humic substances than on pure humic acids.