Fogging Canopies (IMAGE) University of Würzburg Caption With the fogging method, insects and other invertebrates can be collected almost completely from tree crowns. All arthropods that are affected by the insecticide drop into the collecting sheets and are collected for identification. Top right: As a result of drought and ash dieback, most F. excelsior trees had died in 2020. Following a mass development of the ash bark beetle Hylesinus fraxini, woodpeckers subsequently destroyed the bark of dead F. excelsior trees. This gives the dead trunks their distinctive structure. Credit Andreas Floren / University of Wuerzburg Usage Restrictions none License Original content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.