From 1984 to 1993, the lab has worked on the development of a user-friendly sampling technique to monitor for the presence of ELB and predict subsequent defoliation. Since English elm is the most susceptible elm, we have focused most of our efforts on this elm. Since there were no previously established treatment thresholds, we chose a damage rating of 4 as our threshold based on our experience with homeowners and tree managers. 1 Accumulated degree days above 11 degrees C from March 1 in northern CA and the occurrence of ELB eggs and larval stages.
Red lines represent updated treatment threshold.