Japanese beetles, with their metallic green coloring, resemble Egyptian scarabs and are members of the same family. First reported in North America in 1916, according to North Carolina State University, Japanese beetles can inflict a great deal of damage on the landscape, devouring the foliage of trees and shrubs, flowers, fruit and garden crops. Both the larvae grubs and the adult beetles are harmful to the landscape. Depending on the degree of infestation, control may be difficult.
For small infestations of adult beetles, picking the beetles off the plants and crushing them or drowning them in soapy water can be effective.
You can also cover prized plants with cheesecloth during the few weeks in mid-July when adult beetles are most active, to protect the plants from being eaten by the beetles.
Milky spore is a naturally occurring bacteria that kills Japanese beetle larvae. Apply milky spore to the lawn in late September or early October, when grubs are newly hatched and just beginning to feed. Once applied, milky spore will establish itself and multiply, remaining in effect for years
Neem and Pyrethrim
Neem and pyrethrim are natural products that can deter Japanese beetles without harming the environment. Pyrethrim is derived from chrysanthemum blossoms while neem comes from the neem tree. For best effect, these products must be applied every three to four days, and after every rain. Care should be taken to thoroughly coat all leaves of affected trees and shrubs.
Carbaryl (Sevin) is available in both powder and liquid applications. Apply carbaryl powder or spray to the foliage of shrubs, trees and flowering plants to kill adult Japanese beetles that feed on the foliage. Carbaryl may also kill beneficial insects, so should be used only on plants that show beetle damage and in the lowest amount possible to control the beetles.
Spray diazinon on the lawn in mid-September to control Japanese beetle grubs. Water the lawn well after application of the diazinon. You can also spray diazinon on plants in the spring when adult beetles are feeding to control adult beetle infestations.