Evaluation location: Illinois, United States
A male/female pair of field-collected (adult beetles used were field-collected from plants at The Morton Arboretum, Lisle, IL and The Chicago Botanic Garden, Glencoe, IL.) adult Japanese beetles was placed into a 5.7 L (6 qt) capacity Clear-View™ plastic container (SteriliteR, Townend, MA) with approximately 5.0 cm. of finely sifted moist silt-loam soil, and foliage of the candidate Ulmus taxon to be tested. Foliage was kept turgid and fresh using floral water piks. The boxes containing the beetles and foliage were kept at room temperature in the laboratory under natural daylength. The boxes were examined every third day and elm foliage was replaced if wilted or defoliated. At 7, 14, and 21 days from the initiation of the study, the soil in each container was visually examined for eggs, and the total number of eggs per container and adult beetle mortality was recorded. After each egg counting, the original male/female beetle pair was returned to the container. Ten single containers (replicates) containing one male/female pair were used for each of three single trees per Ulmus taxon for a total of 30 beetle pairs per taxon. The study was terminated after 21 days.