Japanese Beetle Control for Roses
Beginning in June, Japanese beetles start to thrive. If uncontrolled, they can destroy nearly all of your summer rose buds and blooms as well as do some serious damage to the foliage.
What do Japanese beetles look like?
Adult Japanese beetles are about 3/8 inch long with shiny, copper-colored wing covers and shiny green thoraxes and heads. The five small white tufts on each side of the wing covers distinguish Japanese beetles from similar metallic green or coppery beetles.
Japanese beetle damage on roses
Japanese beetles are attracted by the scent of the flowers on rose bushes. They start feeding on the top of the plant and move down as defoliation occurs. Damage to plants is obvious and can occur within just a few hours. The beetles produce pheromones that will attract more males and females to feed and find potential mates. This will bring more beetles into your garden, challenging any control program that you may have.
Japanese Beetle Damage on Rose Bud
Japanese Beetle Damage on Roses
Japanese beetles can also cause extensive damage to foliage:
Japanese Beetle Damage on Rose Foliage
How to control japanese beetles
Insecticides. Many insecticides are labeled to control Japanese beetles on landscape plants (Orthene Turf, Tree & Ornamental Insecticide, Bayer Advanced Garden Multi-Insect Killer Concentrate, Ortho Bug-B-Gon Garden & Landscape Insect Killer Concentrate). Some of these insecticides mimic the scent of the pheromones released by the beetles to attract more beetles that then feed on the plant that has been treated. This may actually cause more damage to the plants as more beetles are attracted because insecticides do not work immediately. In addition, repeated applications are necessary and some products may contribute to build-ups of mites and aphids. Directly spraying beetles with insecticidal soap will kill Japanese beetles but does not provide any residual protection.
Traps. Japanese beetle traps are commonly sold in home improvement and garden centers. Traps work by either mimicing the scent produced by female Japanese beetles or with the scent of sweet-smelling bait. The traps tend to attract many more beetles than they actually catch so infestation and damage to plants can actually increase as a result of having a trap in your garden.
Collecting. Beetles are best collected off the plants in the cool of the early morning when beetles are sluggish. Gently shake the beetles into a container of soapy water or pick them off by hand. This can be a very time-consuming process and will have to be repeated daily.
Milky spore. Milky spore is a naturally occuring bacterium that is lethal to the grubs of Japanese beetles. When applied at the proper rate, milky spore is very effective at killing the grubs and thus breaking the cycle of the Japanese beetle. Milky spore occurs naturally and it is not harmful to beneficial insects, pets, etc. Unfortunately, milky spore applications can be very expensive. An application for a 1/4 acre area costs about $100. In addition, Japanese beetles can still migrate to your garden from neighboring properties.
- Natural Controls. The hard body of the Japanese beetle make them unattractive to predators so control via predatory insects is uncommon. Planting companion plants, such garlic or other types of alliums, along with your roses can help repell Japanese beetles and other insects such as aphids and mites. Another natural method to limit damage to your roses is to cut buds early and let them bloom inside. Cutting the buds on your roses during the early weeks of June will limit the damage to your plants.