Colorado and Rocky Mountain Region Plant Feeding Lists, click HERE.
The plant lists below are screen shots taken of the plants lists from the studies found at
https://webdoc.agsci.colostate.edu/bspm/JapaneseBeetle/Held2004.pdf AND
https://webdoc.agsci.colostate.edu/bspm/JapaneseBeetle/Fleming1972.pdf
Please refer to each study for the entire abstract, description of the data, summary and literature cited. Keep in mind that studies were on plants growing in the New England area of the country. Not all cultivars may be available in commerce or recommended to grow well in Colorado. This information is meant as a reference guide.
Plants Injured Most Severely information from pages 62 and 63. https://webdoc.agsci.colostate.edu/bspm/JapaneseBeetle/Fleming1972.pdf
The Held: Susceptibility of Woody Plants to Japanese Beetle list of plants below include many deciduous and evergreen trees and shrubs, including a susceptibility list for crabapple trees and linden trees.
The plant lists below are screen shots of the plant list from Biology of Japanese Beetle Fleming 1972. This is a lengthy list that includes many plant Families of annuals, perennials, weeds, vegetables, trees and shrubs. The preference of feeding scale includes the initials "Do." which stands for Ditto. This refers to the plant part of feeding or none listed directly above (foliage, flower, fruit).
The sources for the plant lists above -
Relative Susceptibility of Woody Landscape Plants to Japanese Beetle David W. Held 2004
Biology of Japanese Beetle Fleming 1972 The plant lists start on page 61 of the actual document, or page 67 of the pdf.