Japanese Beetles in Brambles in the Home Fruit Planting

Leaves and fruit on the upper parts of the cane are affected more severely than the lower portions, as the beetles prefer sunny areas.  Different varieties of raspberries and blackberries vary in their attractiveness.

Japanese beetles spend the winter and spring as larvae in the soil, feeding on grass roots.  Adult beetles first begin to emerge from the soil in late June or early July, with the highest populations being seen from mid-July through mid-August.  Populations begin to decrease afterward, but the beetles will be present into September.  Populations vary from year to year.

Beetles exude a pheromone that attracts more beetles, so it is helpful to control them while their numbers are still low to minimize further attraction to your planting.  This is the same principle on which Japanese beetle lure traps work, so it's best not to place the trap right in your berry patch.  Beetles can fly substantial distances - over a mile - from other grassy areas if motivated.  When disturbed, beetles fall towards the ground briefly at first, then attempt to regain flight.  Hand removal by either holding a plastic bag below a branch and tapping it to catch the beetles or by using a bucket of soapy water works for small numbers of plants.  Weekly inspections and beetle removal from the time beetles are first noticed until they are gone are recommended.  Insecticide sprays can be used, but given that fruit is present on the plant at the same time as the beetles, other control methods are preferable.