In this paper we aimed to present the results of the monitoring and forecasting the occurrence of the most important harmful organisms in forests and plantations in the province of Vojvodina, Serbia in 2018. Many harmful organism were shown to be present in Vojvodina, including many species of insects and fungi. Based on observations and the use of forecasting models and modules, we made predictions of development and recommendations for the control and suppression of most of these pests. The pathogenic fungus Hymenoscyphus fraxineus was isolated from the symptomatic tissue of Fraxinus angustifolia and the fungus was morphologically characterized. Therefore, we confirm the presence of the fungus on narrow-leaved ash in Vojvodina.