Japanese Beetles Diagnostic Guide
Native to Japan, the Japanese beetle (Popilia japonica) was first detected in New Jersey sometime around 1916. It has since spread to nearly every state east of the Mississippi and continues to spread each year. The adult beetles are skeletonizers, which means they feed on the leaves of trees by eating the tissue between the leaf veins. Severe Japanese beetle infestations can completely devour all of the tree’s leaf tissue, leaving only the veins behind. They will often feed on flowers and fruit as well.
Trees at Risk
Japanese beetles attack over 400 species of plants including many trees and shrubs such as linden, crape myrtle, flowering crabapple, Norway maple, Japanese maple, flowering cherry, elm, sycamore, black walnut, horse chestnut, plum, gray birch, and others.
Japanese beetle attacks a broad host range of shade trees, shrubs and other woody ornamentals, as well as fruit and vegetable plants. Soil applications of Xytect or Lepitect will provide acceptable levels of stand-alone control. If clients have a low threshold for leaf damage or if infestations are high, consider combining soil applications with a foliar spray tank mix of Xytect and Tengard during the adult flight period.
Spray treatments are required once adult feeding occurs on trees that have not been treated preventively. Tank mixes of Xytect and Tengard will provide a high level of control for 14-21 days. Sprays should begin at the early onset of adult feeding. Protecting trees against early feeding is extremely important. Japanese Beetles are attracted to trees that are being fed on by other beetles.
- When the soil-applied systemic products Xytect or Lepitect are applied, the beetles are not prevented from feeding, but they do die after they feed. Some defoliation should be expected even on treated trees. From a distance, trees will look fine, when viewed up close you will see some damage.
- Combine soil applications with foliar spray applications for clients with low tolerance for leaf damage or in areas that have a history of severe infestations.
- Feeding adult beetles attract more adult beetles to attack.