Control of the soft brown scale, Coccus hesperidum L : in greenhouses of botanical gardens

Abstract: In this bachelor thesis, the control methods for the soft brown scale, Coccus hesperidum L. in greenhouses of botanical gardens, were discussed based on the knowledge gained from a questionnaire answered by gardeners from botanical gardens. C. hesperidum is a common pest in greenhouses. However aggressive ants make it difficult for the natural enemies, released as biological control, to parasitize and predate the pest. The greenhouses of botanical gardens are artificially made environments in semi-closed ecosystem, and the dynamics and the environment in the greenhouses can easily be disturbed. The botanical gardens have rules and normal procedures, which the gardeners have to respect. The preferred method of control is biological control, but in exceptional cases chemicals could be used. This study aimed to examine which methods are suitable in the greenhouses and where further research is needed. I found that C. hesperidum had many different methods of control. Biological control does not always work as intended because it affects many different trophic levels that have to be accounted for. Chemicals can be necessary, if the natural enemies of C. hesperidum do not work as expected. Pheromones are used for bigger crops, and further research for non-chemical treatment for smaller use is needed. Spread and arrival of new pests can often be avoided.