|
|
Insect pollinators issues and alternative methods of control of fungal, bacterial, and parasitic diseases of bees
MRÁZ, Petr
This Ph.D. thesis is focused on the importance of insect pollinators and pointed out to their loss due to intensive agriculture. Great attention is paid to the honey bee as the main pollinator, especially to the issue of quality nutrition of bee colonies in connection with the support of detoxification of pesticides. Furthermore, the main effort is devoted to alternative possibilities of control of selected bee pathogens and research of their prevalence in the Czech Republic. The work is divided into two main parts: a detailed background research and an experimental part consisting of six subchapters with results from my own research studies. The first study deals with the effect of pollination on the qualitative and quantitative yield parameters of honeysuckle. Several pollination variants were tested and the best result in all monitored parameters was achieved by the pollination with natural pollinators. Variants of manual pollination and without pollination caused uneven maturation of fruits and lower yields. Furthermore, the diversity and abundance of pollinators in the vicinity of this crop were observed and the most suitable pollinators identified which appear to be bumblebees and the honey bee. The second study deals with the impact of agricultural intensity on the diversity and abundance of pollinators in the landscape. Localities with organic and conventional management regimes were compared. Significantly higher diversity and abundance of pollinators was recorded in the locality managed by organic farming. In addition, the contamination load of pesticide residues in bee's body was also monitored. Residues of several pesticides were detected at the site with conventional agriculture, while none of them were detected at the site with organic farming. The third study examines the effect of nutrition, specifically phenolic substances, on the ability of bees to detoxify the pesticide to which they have been exposed. In the experiment, the bees in the cages were fed with a mixture of selected polyphenols, commonly found in pollen, and the pesticide thiacloprid. Mortality and daily feed consumption were monitored for 14 days, and the expression level of detoxification genes was analyzed at specified intervals. Phenolic substances have been shown to have a positive effect on the lifespan of intoxicated bees, as well as higher feed consumption, which may indicate an increased need for these substances. In contrast, the increased expression of detoxification genes was not confirmed. Other studies focus on honey bee pathogens. One of them monitors the occurrence and prevalence of selected major bee pathogens in the Czech Republic and compares different types of habitats, such as urban areas, agriculturally intensively cultivated areas and protected natural areas. Surprisingly, the most often detected pathogen was Lotmaria passim. From the viral diseases, the highest rate of occurrence had DWV complex and ABPV. In general, more eukaryotic pathogens were found in cities and agricultural landscapes. On the contrary, more viral diseases were recorded in the protected natural area. The fifth subchapter consists of 4 publications and deals with the use of essential oils to control the Varroa destructor mite and the entomopathogenic fungus Ascosphaera apis. The first publication compares the growth and development of the fungus A. apis on different culture media and proposes a new medium with the addition of bee brood, on which the greatest sporulation was recorded. Another 2 publications deal with the fungicidal effect of selected essential oils in laboratory conditions. The best results were shown by essential oils of thyme, cedar wood, cloves and cinnamon. The fourth publication deals with the acaricidal effect of selected essential oils on the V. destructor mites and at the same time evaluate the toxicity of these oils to adult bees. Based on these results, essential oils with the highest LD50 to bees / LD50 to mites ratio (sele
|
guest ::
