In the months of June and July, Japanese beetles swell in population just in time to destroy rose gardens. Attracted by the smell of the flowers, the beetles feed on buds, leaves and stems. Pheromones released from beetles attract more pests looking for mates, adding to the problem. If you fail to get rid of Japanese beetles, you may lose your entire rose garden.
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You can often reduce the amount of trouble you'll have with Japanese beetles by killing them in the grub state. As grubs, the pests develop under your grass. According to Landscape-America, a female Japanese beetle lays between 40 and 60 eggs. Left unattended, these grubs develop into mature, rose-eating adults.
There are several options you can take to kill the grubs. In some regions like the eastern United States, Bacillus popilliae Dutky, also known as bacterial milky diseases, works to kill the grubs. Parasitic nematodes also work as a way to reduce the grub count. Products containing Steinernema carpocapsae have parasitic nematodes in them. There are also chemical lawn applications containing trichlorfon or carbaryl, which you can purchase from home improvement stores or landscaping nurseries.
Collecting Japanese beetles and dumping them in a can of oil or soapy water is an effective way to kill the pests. Early morning is the best time to collect the beetles. In order to be effective, you need to search your plants every morning until you no longer see signs of infestation.
Another way to kill the pests is to spray soapy water or insecticides on your plants. The soap deters the beetles from feeding, leaving them to starve. The insecticide mimics pheromones, attracting the beetles to the poisoned area. Some people feel this can cause more damage as it attracts beetles, but others disagree.
Some people think natural enemies like chickens and other birds help with Japanese beetle control. Birds often eat beetles and can be a good way to keep a beetle population in check; however, the hard shell of Japanese beetles protects them from this approach. Another misconception revolves around the use of traps. While manufacturers market traps as a way to get rid of Japanese beetles, the trap can actually attract more of the pests without the ability to kill them.