Evaluation location: Ohio, United States
Trees sampled were planted in Indian Mounds Park as part of the National Elm Trial. For all cultivars except for the ‘Valley Forge’ (only two trees available) at the Indian Mound site, three trees were randomly selected to be part of each evaluation. Ten leaves were
randomly selected from each tree. For the majority of the trees, these leaves were collected from
the lower branches which could be easily reached without assistance. For some of the taller
trees, a pole pruner was used. Leaves were selected evenly from all directions, as much as
possible, and were picked both near the trunk and near the tips of the branches to give a wide
breadth of coverage. Leaves were then placed in plastic, zipper-sealed bags labeled with the date
and tree number. After all samples were collected, they were brought back to the laboratory and
either were evaluated immediately or put into a refrigerator (40F) until they could be evaluated. The data from each sample of leaves were recorded within 48 hours of the leaves being picked. For each sample, the total number of adult feeding holes was recorded. The total number of larval
mines in each sample was also recorded. Finally, the length of each leaf was recorded. This measurement was used to estimate the area of each leaf by using the formula for the surface area of an oval (SA=0.5L*0.5(0.67L)*π) where L is the measured length and 0.67L
represents an estimate of the width. Although this estimate is not an exact measurement of the
surface area, this step was necessary normalize and compare the adult feeding damage per leaf
area. The total number of holes in the sample was then divided by the combined surface area of
the ten leaves. The final adult damage was then recorded as the number of holes per surface area
of leaf (holes/cm2)